Hi,
I recenlty came across a post on Audi-Sport from a member who had his misfire mystery solved by kind members of this forum. I'm hoping you can do the same for me.
My Audi S3 (2001) AMK keeps having multiple misfires across cylinders 1,3 and 4. Coil packs are new, new MAF, new plugs but still a misfire. I used VAGCOM to log the misfires by cylinder and found that they only misfire when I take my foot off the throttle and coast.
Looking at the Engine error codes I get...
4 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16687 - Cylinder 3: Misfire Detected
P0303 - 35-10 - - - Intermittent
16688 - Cylinder 4: Misfire Detected
P0304 - 35-10 - - - Intermittent
16685 - Cylinder 1: Misfire Detected
P0301 - 35-10 - - - Intermittent
Readiness: 0000 0000
Through research I understand it could be the injector amplifier? I have the car in this weekend to MRC Tuning who are installing new injectors, fuel pump (it's done 100k miles!). Not sure if the injector amplifiers come with the new injectors but we'll have to wait and see.
The car has already blown a HG when cylinder number 1 head cracked and leaked oil round the seal. All now reconditioned after a £2k repair bill.
Anyway, I really don't want another big repair bill so I would really like to solve my misfire asap. Can anyone help shed any light on why the misfire would ONLY be happening when my foot comes OFF the accelerator?
Thanks for listening guys.
Cheers,
Gav
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Does sound as if there might be a little fuel problem, perhaps a little getting in when the foot is off the throttle causing it, rather than al the injectors shutting off?
Doubt it's ignition if your not getting it under power.
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Sounds like an air leak, as you take you foot off vacuum is created in the inlet, could it be sucking in air. A split rubber that leaks under vacuum though not under boost, might be working looking at pipes, joints etc.
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Yeo due tho the random nature of the misfire and the closing comment of missing when you take you foot off then I to would be looking for an air leak, vacuum pipe fracture inlet manifold gasket. Sray all seals,gaskets pipe joints and bends with carb cleaner, if the engine ingests it the engine note will change. I assume this misses at idle. Changing all the injectors and the fuel pump is going to be a bill bill and I no not think it will fix it. Regards Peter
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So the injectors don't shut off on this engine on the overrun...so it's gets any fuel I was sure it did for economy reasons?
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if you still have trouble try a BOSCH approved garage, I find they are VERY good with ignition systems.
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Hi Chaps,
Thanks a lot for the responses guys, that gives me some more to go on.
I've just dropped the car off at MRC and mentioned that the car was still misfiring. We did already run a pressure test and it all seemed good - however I'm guessing this wouldn't identify a leak in the vacuum system??? He just connected a pipe to the air intake and pressurised the system.
Anyway, now I have this info I will pass it on to MRC and see if we can find the problem.
I'll report back once I have some news.
Thanks again.
Gav
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No they do not shut off as the car would loose the emissions control, unlike a diesel that does shut off completely on the over-run. Of couse this explains why big exhausted chav cars backfire on the over-run as some ( small amount) of fuel is still entering the system. Regards Peter
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No they do not shut off as the car would loose the emissions control unlike a diesel that does shut off completely on the over-run. Of couse this explains why big exhausted chav cars backfire on the over-run as some ( small amount) of fuel is still entering the system. Regards Peter
Ta, they have obviously been making some changes over the years when I wasn't looking. It was quite common to shut the injectors off to save fuel...didn't realise they had stopped the practice, it seemed like a decent idea.
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Any developments on the problem, just I've got a very similar fault with my 55reg A3 2.0TFsi.
The car seems to run fine with no noticeable lack of power, but when you press the clutch in whilst changing down gear the engine revs rise to around 2k then drop off as normal. When the car is just ticking over the revs hunt around between 850 & 2000 rpm.
I've taken it into a local garage who ran a diagnostics & found 9 fault codes including misfiring etc. (unfortunately I didn't record the faults). They thought it was the coil packs but this never solved the problem. The fault codes have been reset & I'm waiting for the light on the dash to come back on before taking into another garage? After reading several forums it seam?s split air pipes or faulty MAF sensors are common.
Is it possible to check operation of the MAF sensor?
Any feed back appreciated.
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Any feed back appreciated.
Ask these people:
www.bba-reman.com/uk/index.aspx
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My car now been in to Audi garage for diagnostics and fault found to be a collapsed non return valve on the air intake system. Part replaced and so far its running good.
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I am having this misfire problem on my 03 S3. My codes also say the same thing, random misfire. I just want to be sure that is the PCV valve, because I don't have it right now, I had to change it, so actually, there is the hose without anything, only a screw to prevent something enters. Also, my fuel pressure regulator hose is broken, And I'm waiting til' monday to get it replaced. Which is exactly the valve you replaced? Thank you. From Venezuela.
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