AMAs seem to be the cool thing to do lately, so thought I'd give it a try. Have been a mechanic for 15 odd years, worked on everything from Hyundai to Porsche. Recently moved to marine in the last year or so. Will try to answer when I can.
Edit - Wow this was much more popular than anticipated, thanks for the great response everyone, hopefully it's helped a few people out.
Ta for the AMA.
What are your thoughts on changing the oil only every 15,000 k's? The service schedule of our new diesel is only for an oil change every 15,000, but I'd had it drilled into me by a parent that it should be every 10,000, no matter what the schedule says?
Your parents are old and are unlikely to know more about a modern car's servicing needs than the engineers who designed it.
Oil can be replaced as frequently as you can afford it, but if what's in there hasn't reached the point where it's no longer providing adequate protection then replacing it is wasteful.
Changing at 10k definately won't hurt it. Longer service intervals can be ok when better oil is used. I personally don't trust the 30k km intervals though, and there is no way I would leave it that long in my own car that I wanted to keep. The extreme intervals sure do make them attractive when on lease though ;)
I don't have much experience with diesels but it's pretty amazing how unused the oil in modern petrol cars looks after 10,000km. Goes in like honey and comes out looking like slightly darker honey.
@Pantagonist: It's more the additives that break down over time/temperature/wear that you can't see. However, in a diesel, the oil is generally black the first 30 seconds after you start it after just changing the oil, people often think you haven't actually serviced their cars.
What's your thoughts on Penrite? Been using the Enviro 5w/30 in my late model Mazda3 SP25 (I change every 8k/12mth).
PS: This is the best forum thread I've read on here in years. Refreshing to see compared to the usual nonsense.
Penrite is great. I only use their run into in oil in motors I build. Also run their extra zinc in my pathfinder, and their enviro+ in my Passat.
Thanks mate. Happy i made the right choice
My 2010 Subaru Impreza has an engine code - H02S (Heater COntrol Circuit Low Bank 1 Sensor 2)
Is this something you're familiar with? Easy to fix?
https://www.obd-codes.com/p0037
Fixing oxygen sensor codes on Subarus can be as easy as replacing the sensor itself (if it has failed) and as difficult as tearing apart the whole emissions system to fix an issue further upstream that causes the PCM to throw a code that's unrelated to the actual issue.
If you're relatively handy and can locate, remove and reinstall a new sensor yourself then that is generally the cheapest option provided you buy online and know what part you need. If it fixes the problem, great. If it doesn't, you won't be too out of pocket.
That is sound advice. Now to find out which sensor and where to get it.
@Pantagonist: Thanks, Nomandesque! You saved me some time. I didn't realise the significance of the P0037 code that is showing on my ODBII reader. This looks like it'll suit nicely.
Hi Brendanm, Thanks so much for this great AMA. I have a 2010 diesel Hyundai Santa Fe. the battery warning light is on an off intermittently. have tested the battery with multimeter and battery analyser tool, showing good health and correct voltage, 12.6-12.7 volts when engine is not running. Also tested the voltage delivery from alternator, showing acceptable range around 13.9-14.1 volts when the engine is running. I noticed the warning light is almost always triggered when the weather is hot or after the car has been parked under the sun. I did a test with short trip and long trip (150km) with the warning light on, hoping the car would break down somewhere and it still hasn't happened yet. Strangely, sometimes driving it all day can make the light goes away for a couple of days or so before it switches back on again. Turning on/off the air con for a couple of times, could also make the light disappear but doesn't always work. What could be the issue? Appreciate you help in advance.
G'day,
this sounds like problem I had with my 2004 Toyota camry grande V6. my car audio and air condition units were keep turning off then comes back on short second later, this always happens HOT days. sometimes whole car shook then lost the ignition. (yeah very dangerous while you are moving)
First I thought the battery not working but checked out with battery diagnostic machine the Battery were fine.
at the end I found out that it was the ALTERNATOR was ONLY working intermittently; the alternator stop working when the car warms up.
so the the electrical system in the car not getting enough amp power due to intermittent charge from the faulty alternator.
it took almost 3 months to diagnose the problem as if the alternator were producing power when cold start but stopped once car warmed up.
I would check the alternator if it is charging/producing power to the battery.
I would check the alternator if it is charging/producing power to the battery.
Maybe, but…
Also tested the voltage delivery from alternator, showing acceptable range around 13.9-14.1 volts when the engine is running.
Sounds like a different issue to yours, especially as they've driven long distances without any of the electrical issues normally associated with a battery that isn't being adequately charged.
To rule out a power supply issue you could try and do a load test while the vehicle is running. This involves turning every electrical accessory on in the car at the same time (e.g. headlights on high beam, AC on max, window de-icer etc.) to see if engine performance is affected. It's worth keeping the multimeter connected to the battery while you do this to see if the voltage drops below an acceptable level.
Another thought I had was that it could be a voltage regulator issue (i.e. the charging current isn't stable and is actually reaching a voltage level that could damage components). Could be why clicking the AC on and off a few times sometimes fixes the problem as you're hitting the battery with spikes in demand which resets the light as the charging voltage reduces to an acceptable level.
Hi Nomadesque, thank you for responding. I have driven the car with the headlight on, not on high beam though; with AC at 75% to max, didn't feel any noticeable performance loss from the engine. Will do your suggested test with heavy electrical load.
How do we perform a test to isolate voltage regulator issue?
@movi4c: https://youtu.be/1bK0De9XOP0
This video should have everything you need.
It would also be helpful to find out the correct alternator charging voltage range before testing (as outlined in the video). Typically this will be in the factory / workshop service manual for your car which may be obtainable online or through eBay.
G'day hongas, appreciate your response. About the air conditioning unit, mine wasn't actually turning off by itself. The battery warning light sometimes goes away if I switch on then off the air conditioner for a couple of times. Sorry, if I wasn't too clear in my original comment. I did checks on the alternator when the car is warmed, it was charging and producing the correct voltage range. Did the test a few times throughout the day when using the car, always gives me the correct power. I also did the cranking test to see if the voltage drop below 10V, it didn't. So, I am still puzzled where the problem actually lies.
What voltage is being put out when then light is on? This is an interesting one, your car has a "one way clutch" on the alternator. The normal failure mode for these is to lock, and no longer provide the clutch function. However, they can also fail by slipping and losing drive. They are relatively easy to check if you remove the serpentine belt, then stick a screwdriver or similar in near the front of the alternator to lock the internal bits to the housing. Then if you turn the pulley, it should turn freely in one direction and not turn in the opposite direction. If it is sticky, grindy, rough or locked it requires replacement.
Failing that, it's most likely the voltage regulator in the alternator, so a new alternator is required, as noone really repairs them anymore.
Hi Brendanm, Thanks so much for your reply. On Low beam, it is 14.1 volts, High beam gives 14.2 volts. Are these okay? Haven't tried removing the serpentine belt yet.
Sorry I meant when the alternator/battery light is on, have you measured the voltage?
@brendanm: Yes, I have. When the battery light is on. the voltage is showing a range between 13.9-14.1 volts as if there is nothing wrong. The alternator seems to be doing its job.
@movi4c: Sorry missed this reply. That's very odd, it may be an issue in the voltage regulator itself? Haven't struck it before.
@brendanm: Hi brendanm, I'm sorry too, didn't know that you replied and not aware that the AMA is still going. MASSIVE thank YOU for this awesome AMA. Learned a lot. I'm planning to replace the alternator, but just had a thought, could the issue be electrical wiring? like improper connection, wires going bad, rusty pin. If you think this could be a possible culprit, would you mind to point me where to check? Thanks again.
@movi4c: All good mate. It's unlikely it's something like that, as it would (likely) be happening all the time. Before you do the alternator, under the wiring connector and have a look at the terminals. Should be pretty obvious if there is anything wrong there.
Awesome AMA Brendanm! What are your thoughts on capped price servicing vs indy servicing specifically MMA. My case, recently purchased a used 2016 MY16 NX Pajero (pre-DPF) with 45k on the clock (just been serviced prior to purchase). 60k service will be due early next year and according to MMA capped price servicing will be $800. Items replaced according to the maintenance schedule https://www.mitsubishi-motors.com.au/uploads/maintenance-sch… will be:
-Coolant
-Brake fluid
-Fuel filter
-"Air purifier" filter (cabin filter?)
-Engine oil and filter
Rest are inspection items apart from lubing some suspension component and prop shaft.
Also installed a Mann & Hummel catch can (and an EGR defeat device), do you recommend I remove the the catch can (EGR defeat will definitely be coming off) if I do my next service at a dealer? And lastly would you see any benefit in doing an inlet manifold clean (last owner only did city driving if that means anything) at this mileage?
Thanks in advance!
OP posted his comments here about capped price servicing.
Personally I would have thought that an independent mechanic would come in well below $800 for that service. You'd also be saved the hassle of removing your mods and reverting to stock. Stuff like the air purifier probably doesn't even need doing unless you've been driving in dust storms without the air recirculation on.
As for the intake manifold clean, I'd be surprised if a car with 60K on the clock needed it unless it had serious mechanical issues. As you've deleted the EGR there won't be any exhaust gases getting recirculated so the manifold should only be getting clean air passing through now.
Thanks, yes just saw the other comments about capped price servicing after I posted. Will probably opt with an indy for the next service.
Brendanm, do your thoughts differ to this?
They do slightly. I agree an Indy would be much cheaper. Personally I would check the cabin filter, a bit of stuff on them can really lower your blower fan output, and some of them are absolutely filthy.
Cleaning the intake manifold is a good idea as you have only recently done the EGR delete and catch can, they get absolutely filthy on the Mitsubishi's for some reason, the 2.5s even worse than the 3.2s. At least then you will know it's good, and EGR delete and catch can will keep it that way.
I am very interested in tyres/rubbers, I know it’s odd, what are the chances for a 35 middle age IT guy to get into this field and run their own rubber / suspension shop? What would be the most effective path?
There is a lot of money in tyres if you are into marketing. Suspension work can be very hit or miss, the most money is in lifts for late model 4wds, as they are clean and easy to work on, there are kits for all of them, and people are happy to pay if it looks good and rides acceptably. Works well with the tyre business, as they also want larger wheels and tyres to go with the lift. It's something you can own without having to have an insane amount of knowledge of you had one mechanic and a few tyre fitters.
I worked in the retail tyre / suspension / brake industry a long time ago. One of my bosses did similar to you.
He started by finding the most successful tyre shop (it was a discount place) in Sydney, getting a job with them and working like crazy for 18 months to learn how they made money. He started as a fitter but got a new job every couple of months because he wanted to learn. He also made contacts / networked. Then he opened his own shop.
I'm not sure about elsewhere but in Sydney it's a fairly cutthroat business and there's lots of competition.
A really good alignment tech would help your business as most of them are just green zone jockeys and don't really understand the finer points of what they are doing.
I suggest you try before buying as you are dealing with customers and either their pride & joy or with people that really resent spending money on their car. They can be difficult.
We worked at a corporate store that had the highest sales figures in NSW. Three of us seriously contemplated starting our own shop and decided it was too expensive (back then) to do it properly. Maybe it's different now. My apprentice opened his own shop and has been very successful.
I have a Peugeot that needs it's turbo replaced (according to the mechanic) and it's proving to be rather expensive. What turbo company do you recommend so I can buy a new turbo?
Also do you recommend the ones you can buy on ebay? They are cheap but not sure if they will last. Cheers
What is wrong with the turbo? Is it a petrol engine with turbo right at the front as you look in the engine bay, leaking oil?
If it does need a turbo, places like gcg or Mrs can rebuild yours, or supply a new one if it's too far gone. I personally wouldn't trust the eBay ones on a car I wanted to keep.
Yes petrol engine and turbo is right at the front and no oil is leaking. Only thing I can notice is the car finds it hard climbing a hill. The speed goes down and no matter how hard I am pushing the gas it only goes like 70-80 km/hr.
No worries, only reason I ask is that it's common for the oil feed line to crack, and people think the leak is the turbo.
Do you hear a loud whooshing sound like air escaping when accelerating? If so you may have a leak in the intake tract somewhere. If not, it's definately possible that the turbo is seized, have you serviced it regularly? Turbos don't seize for no reason, and I'd be worried that the oil feed line is blocked as well.
@brendanm: No noise or any leaks at all. You wouldn't know anything is wrong untill you try driving up a hill. Sadly I don't know the service history as I only just bought the car second hand 3 weeks ago. I was stupid enough not have it checked prior to the purchase.
@Meercat: Oh ok, no service books? It probably has missed quite a few services, this cause the oil to coke up and block the oil fees to the turbo, causing it to seize. I would recommend having the oil feed line replaced at the same time as the turbo.
I've got a 2002 2WD Hilux. Every now and then (1/2 times per drive) there's a random single loud click/clunking noise (sometimes a loud clunk and sometimes a quieter clunk) that comes from what I think is the right rear suspension. Sometimes it happen or a bump, sometimes it happens on smooth road, sometimes at 60km/h and sometimes at 20km/h, so I can't really figure out what sets it off. Any ideas what it might be? :)
Leaf spring suspension isn't complicated so there are only a few things likely to be causing the noise if it is actually coming from there.
Best would be a visual inspection of the front and rear bushings that connect the leaf springs to the chassis. If you can see cracks in the bushing material then it's replacement time. When I first bought my ute the person I purchased it from said that it had failed inspection due to cracked bushings. When I took them off the pivot bolt had worn all the way through and it was metal on metal.
Second suggestion would be to check the rear wheel bearing for play. Get the rear up on jack stands and check for play in all directions (up and down, in and out, side to side). Given the wheels a spin too and check for noise or binding.
From the description of your noise it sounds more like worn bushings if it's only an intermittent clunk or click.
Bushings were my suspicion as well, the same suspension is squeaking as well. Got a few other issues I need fixing as well so I'll be taking it off to the mechanic in a couple of weeks anyway.
As above, sounds like a bush issue. Not uncommon for the shock bushes to wear a lot on those, as well as the spring shackle bushes. Very occasionally you will get one leaf spring in the pack that will break, again making random noises sometimes.
Thank you for the AMA brendanm. Awesome stuff!
My 2010 Camry has done 65k & has lifetime oil in its auto gearbox, surely it needs changing!?
When I do the engine oil/filter change every year, I always think about doing the auto gearbox but it looks so scary!
Where is the gearbox oil filter located & oil pour in hole? Any advice on oil type & quantity? Should engine be running when checking oil level?
Don't remember but I'm assuming the drainage nut is as easy to locate like it is on the engine.
Instead of doing a full flush, if I change now and repeat at 80k, is that enough to catch up on changes or should the 2nd change be sooner than 80k?
Then change every 40k as per your other comments - so helpful!
What's the change interval for brake fluid, power steering fluid and coolant?
Think they’re not hydraulic powered so how often should the engine valves get adjusted?
Every 20-30k or if they start rattling (tightened ones don't rattle) or as per service book every 90k?
My mechanic tells me it's an expensive job (how much?) and so far hasn't done it but I worry they're overdue.
Many thanks brendanm!
Assuming it's the U760E transmission, follow this guide.
Most modern transmissions don't have an easily replaceable filter that you can get to without dropping the whole thing. Basically you just follow the steps in that instruction sheet and repeat as many times as you want to flush as much of the old stuff out as possible. When you cycle through the gears after filling with fresh stuff that's generally when the torque converter gets flushed out and dirties up your new fluid. For fluid type just search for the recommended one using the website of whichever fluid manufacturer you want to use.
I'd consult the FSM for other fluid change intervals.
Assuming the engine is the 2AZ-FE, here are the valve clearance instructions.
As you said, probably a big job and it doesn't look like the valves themselves are adjustable. The lifter itself has to be replaced to keep the clearances in spec which involves pulling camshafts etc. Sounds expensive. Just so you know, valve clearances normally tighten up over time so you generally reset them to the widest clearance recommended.
Pretty sure you should have a 5 speed auto still in a 2010, which means you should have a dipstick. You can simply remove the drain bung in the trans pan, drain your oil, then refill through the dipstick tube. Yes you check with the engine running, and yes your plan of oil changes sounds good. From memory, dropping the pan to do the filter requires a slight dropping of the subframe to get to the front bolts, I definately wouldn't worry about doing that every 40k.
90k would be fine for valve clearances, as stated above, if they need doing, you need to remove the cams, as well as having to purchase the entire lifter bucket with the correct clearance, as they don't have seperate shims. I would be very surprised if you had any clearances that were out of spec at 90k.
Brake fluid and coolant is more time based, generally every 2 years for brake fluid, as it absorbs moisture, reducing its effectiveness and causing corrosion. You should have super long life coolant, which is good for about 5 years. We always just used a brake fluid tester, and a refractometer for checking the coolant.
So if a car that has done less 50k kms in 8 years hasn’t had a coolant change but the refractometer comes out ok, do you still need to flush and put in new coolant?
Technically not, but I would seriously doubt that it would after 8 years, coolant breaks down and turns acidic over time.
Great AMA,
Why do certain cars require specific service intervals, that vary so wildly?
Ie Corolla is 10,000km, some French cars are 15,000km, whilst others had 30,000kms.
Is there a large risk by servicing it 1,000km later, etc?
Some use better oils, e.g. recommend only a synthetic. Some are rather generous at 30k km, which looks good on pricing when doing a vehicle on a novated lease. 1000km is neither here nor there really. The main problem I see with the extremely long service intervals, is that nothing else in the car is getting checked. Your brakes could be about to go, tyres could be bald, you could have a dodgy hose that is about to blow and overheat your car on the highway. It is simply far too long between having it checked over.
Hey so do you think 6 monthly servicing is safer?
Completely up to you. Yearly is fine, but if you are hitting the 10k/15k mark at 6 months, do it then.
Recently bought a boat with a 115hp 2 Stoke Mercury (The Tower of Power). The engine is old (37 years) and has been serviced / water pump done.
It works great but, considering its age, it there anything I should be careful about? I know 2 stokes generally are ok with high revs but is there a risk of damaging it when pushing her hard while towing etc?
Not really, the main thing is to use a good water seperating fuel filter, and good oil. Water and other rubbish in the carbs can cause blockage in the jets, which can cause a cylinder to run lean, causing damage. Good clean fuel, good oil, and a good water pump will see that thing last a long time.
I assume the lower unit oil was done during the service?
How much do you think the coming electric car era will impact the auto-mechanic industry? I'm talking over the next 10-20 years
Probably quite a lot. A lot more mechanics will have to get trained up with high voltage dc and electronics. The vast majority of the car remains the same, just the propulsion is changing, and people will need to adapt to that. People will be much happy going to one shop that can do the electrical side as well as the mechanical side, rather than a seperate shop for each.
Thanks you for the AMA, very entertaining and informative
My dad's car, corolla fielder 2006. At night, from cold start, when the car starts moving, it squeaks from the right hand wheels area seems to get louder as i press the pedal but then the sound disappear after a minute or two.
Doesnt squeak/squeak much less, ends sooner, when you run the car in mid day
When the car starts moving, or when the engine starts running? If when the engine starts, it would be the fan belt or tensioner.
If it's when the car starts moving, you possibly have worn brake pads on the front, and the noise is the little metal tag that tells you when the pads are worn, scraping on the brake rotor.
when the car start moving. it last for up to a minute ish, if i brake, the sound disappears. once the sound disappears, if i turn the car off and on again it doesn't appear again (until the next night or so), but sometimes stopping at traffic lights and the sound starts again as the car moves again.
It makes a higher pitch sound as im accelerating, less if im braking, none if im stopped
I'll see if I can measure the brake pads indicator
Sounds like the brake wear indicator, if it has alloy wheels you can often see the pads without taking the wheel off, it's normally the inner pad that has the indicator on it though.
I recently replaced the fuse for the cigarette lighter/Charger in my Ford Fiesta but is still doesn't work? What would I need to do now?
Thanks in advance I'm just leaving work and wont see any response until Monday.
Did it suddenly stop working, or only after someone did something with the car? Was the fuse blown? Have you tried the socket with a different thing plugged into it?
Yes, the fuse was blown.
Have you tried it with a different device than was plugged into it? The device itself may be faulty, and blowing the fuse
Was the old fuse blown? Could be wiring or similar, just check the back of it for obvious issues. Could also check voltage at the fuse.
Yup fuse blown. I did check the voltage and replaced it correctly but still no joy.
What do you think of Mazda Skyactive G engines?
Same as all the other direct injection engines, more power and torque from the increased compression ratio, better efficiency from the more finely controlled and atomiser fuel. Mazda a generally pretty good, with a couple of exceptions.
What car do you drive? Do you buy repairable write-offs, fix them up and drive them daily?
Answered earlier, diesel r51 pathfinder, diesel be Passat. No I never buy repairable write offs, as they would be impossible to sell. I do buy cars with large mechanical problems, fix them, and sometimes drive them for a while, sometimes sell them.
Regarding a battery replacement on a euro suv diesel, would you recommend dealership genuine or aftermarket installed by battery specialist centre?
Aftermarket. You can get a better battery for a lower or similar price. Them prices dealerships want for batteries blows my mind, especially anything with stop/start.
Any thoughts on the Megane RS (apart from the fact it's French!)? I'm thinking of buying a 2013…
Great thread, just read it top to bottom! Thanks :)
They are a nice enough thing, but expect parts to be expensive, and resale harder than something like a gti or golf r. If you can live with the "french quirks" it'd probably be worth the issues for the drive.
Hi Brendan, what are your thoughts on the Volkswagen Golf mk7 90tsi (1.4L) baseline Model? I recently picked up a second-hand 2013 model with relatively high kms (just clicked over 170,000) but for a great price I might add. Before I purchased, I read online about the Dsg gearboxes failing so I got a manual instead.
My main concern that I read online is that the these 1.4L engines seem to have a common issue of excessive oil consumption, and I have noticed mine is slowly burning oil, and have had to top it up. In the back of my head I'm paranoid about catastrophic engine fail in the future. Thoughts? and Thanks!
They all burn oil, rings are very weak for economy, it's how all engines seem to be going, it's quite silly. How much does it burn? VW's acceptable figure is something ridiculous like 1l per 2000km from memory
Hard to tell the exact rate it burns it since I've only had it a few months, but I topped it up with 1L to around 90% on the dipstick then 2 months later, approx 1000kms travelled, it was down to around 35%. Thanks Brendan
From high to low on dipstick is approx 1l, so you're probably at around 500ml per 1000km, which isn't very good. What oil is being used in it, and what area of the country are you in?
@brendanm: Yes that makes sense being a 1L range. I am using Penrite Enviro+ Full synthetic 5W-30 (VW approved) and am located in South East QLD. I am a student so can't afford a catastrophic issue, hence my concern about it.
@Stinge Master: It won't make much difference, but a 15w40 will be fine to use in se Qld, and will possibly lower the oil consumption a little, as well as ending cheaper to top up all the time.
@brendanm: Ok Brendan thanks for the tip. I suppose if the oil consumption continues to be high around or above the 1L/2000km point I may consider getting rid of it, so I don't end up broke in case shit hits the fan. Thanks!
@Stinge Master: Not problem. I wouldn't be too worried, as I say, even though it's definately not a good thing, it is not uncommon, and as long as you don't actually run it out of oil it should be fine for a fair while. If it starts using significantly more I'd get worried.
Love the AMA, any thoughts on 1 series diesels? 06-12ish?
I really miss having a nice run around euro!
That era of the diesels had timing chain issues, it wouldn't be my pick, the chain isn't even easy to do as it's on the back of the engine. Basically if it fails the car is economically not worth repairing.
Any idea on labour time to replace? I have an X5 with N57 motor and the timing chain is noisy when cold. Tried 1 step thicker grade oil and no difference. Unsure if I replace all 3 chains or roll the dice… car has done 190,000km full service history (however as you probably know BMW recommended oil interval change is too far apart)
A lot. I would assume 20+ hours to pull engine, strip, replace chains and reinstall. Might be able to do it removing the gearbox but is probably much of a muchness. Could always try replacing the main tensioner and see what happens? Yes extremely long intervals really don't help things like this.
@brendanm: Thanks for the reply- the behavior around this currently is that it is noisy for a second when starting and then under load above 1000rpm for the first 5 minutes. Once the car is warm it goes away. Would that suggest weak tensioner? I’m guessing once oil pressure builds it helps fill the tensioner piston with oil.
@lukeacjm: It could be, bit normally if the chain isn't completely gone, the noise will stop shortly after you get oil pressure, a couple of seconds at max. If the chain itself is stretched beyond what the tensioner can take up, it will normally be noisy constantly.
May be possibly to check cam/crank correlation with a scan tool, to see how far out of time they are.
Hi Brendan. Thanks for doing this AMA; it's gotta be one of the best I've read! Very informative and interesting!
Just hoping for a bit of help. My sister has a 2008 Territory Ghia AWD (~150,000km on the odo). After a recent visit to a mechanic where the transmission was serviced, it's been producing a pretty consistent stutter or miss while under any load. The tacho jumps up and down a couple of hundred RPM while this happens and a possibly unrelated buzz/hum is audible from the dash or centre console. I originally thought it could be an ignition or vaccuum leak issue, but after changing the plugs and coils, the top PCV and cleaning the throttle, the issue still exists. Any ideas, could this be transmission related or perhaps even electrical? Any info would be appreciated. Thanks!
What did the transmission service involve?
In my experience, misfires generally cause a drop in rpm. If you want to know what a misfire sounds like on the car, you can pull one of the coils while the car is running which will give you a consistent miss on that cylinder. From your description and the fact that the transmission has been fiddled with, the increase and decrease in rpms could be the transmission slipping.
If a transmission has been neglected in terms of fluid changes, sometimes changing the fluid can flush out all the particles and crud that contributed to friction and assisting traction in the transmission.
Does the car stutter in every gear or is it only when you take off? What if you lock it into a gear (i.e. put it in L, 1, 2 or any gear other than D) and bring it up to maximum speed in that gear? What if you're cruising then kick it down a gear by flooring the accelerator? Would be interesting to know if the stutter only happens when the car shifts gear.
If you have a decent ELM327 scan tool, there's a program called FORScan which is great for diagnosing Ford issues. I have the Android app but it looks like you can get versions for iOS and Windows. You'll need to buy the full version to access all the features. For misfires, you can use the Mode 6 diagnosis for real time monitoring and logging of misfires by cylinder and injector.
I'm assuming it was a fluid change, but I'll have to confirm more. I thought I heard something about 'seals', but not sure. It stutters in all gears- doesn't seem shift specific. Even 'sports' mode with manual shifting still presents the issue - this is what lead me to believe it wasn't the transmission, but I admit I have very little knowledge of automatics
I'll give FORScan a go. Thanks for the info @Nomadesque!
Finally got around to running a FORScan and it flagged several errors to do with the HIM - HVAC Integrated Module:
B1262-2F
U1900-2F
B2513-2F
U2197-2F
U2196-2F
U1250-2F
Interesting. That module seems to tie in with the PCM and sends / receives data. I suppose it's possible that if there's bad data being sent to the PCM regarding what the HVAC system is doing then the engine might not be compensating correctly for those demands.
You could try turning off everything to do with that system (i.e. no AC, all blower fans off) to see if that makes a difference to the problem.
Any misfire information in the Mode 6 data?
Does it missfire at idle? Goes away at higher rpm? If it's only at idle and low speed, it is common for the inlet manifold gasket to break away at cylinder 1, and cause quite a large vacuum leak.
Sounds very strange. Did you change all the coils? It may be worth checking the fluid level in the transmission just in case, or taking it back to the mechanic who did the work and get them to check it.
Thanks for the reply! Yeah, changed all coils and plugs - thought it'd be a good thing to do considering the age of the car. Is it easy to check the trans fluid level? I heard it may only be checked from the same port it is filled on the ZF boxes?
As above, belt is a good first check, second would be operation of the auto tensioner, they can get weak and/or misaligned. If the a/c is working it's very unlikely to be the compressor.