Missfires

[mnadeem1984]

Arghh!


I've tried nearly everything now! Initially, I replaced the sparkplugs. Using Vag-com I would get the odd missfire at cylinder 3. Then under hard driving, this missfire would occur in the other cylinders too. None of these Missfires are serious, and so the car still does drive smoothly. However, at various intervals, when the missfire occurs, there is a sudden loss of power (which i initially thought, may have been because of the surging).

After replacing the sparkplugs, I swapped the coilpacks, however, the missfire at cylinder 3 was still present at odd times under idle. Whilst driving hard, the missfires still occured at odd intervals.

I replaced my coil pack wiring harness, as the wires had cracked, aneven this had no change.

My question is, what else can be causing this missifiring? The spark-plugs I got were NGK which were preset gap and so I did not alter these. The car is chipped however.

Can you please post ur suggestions as to what else may be causing the missfires please.

 

[mnadeem1984]

bump

 

[petewon]

Can you turn your chip off? If so does it still give the same problem.

 

[mnadeem1984]

No i cant turn the chip off. However, can the chip be causing a missfire at idle too though (i.e for cylinder 3)

 

[petewon]

Good point.

Have you scanned it with VAG? If so can you post the codes?

 

[mnadeem1984]

yeah I have scanned it, however nothing shows up on the faults. These missfires only occur when i view measuring blocks 015 and 016.

Like i sed, its not always there. However Cylinder 3 missfires occur even when idling , not all the time but it does occur. When it does, i feel the idle go lumpy a little and then it goes back to normal again.

As for the other three cylinders, they only occur when i drive the car hard and the missfire count goes up very slowly, (like 1-3) missfires but then the cars back to normal again.

 

[petewon]

Have you tried unplugging the MAF? Might just be a dodgy mixture causing misfires. Althoough I would have expected to see other things on VAG if it was that. Worth a shot tho.

 

[s3shabs]

Had this problem recently, bought a set of 4 new coilpacks..Still didnt have no joy, done a few tests and found that one of coilpacks(the new one) turned out to be faulty! got that replaced, problem solved..

 

[mnadeem1984]

i measured group 032 to check the g/s (or something like that value) and i was getting 166 (which is around 200+ bhp) which is right for a chipped car.

 

[mnadeem1984]

bump, any more suggestions?

 

[J0E]

Im having the same problem at the moment.
Driving the car the other day fairly hard and all of a shot a solid misfire came into the engine so i slowed down and nursed it home. At this time it was mising even at idle so i checked it out and found cylinder three was gone. so fitted new coil. This improved the broblem but didn't solve it. It now only misfires when it comes on boost under sharp acceleration. Today i replaced four plugs and four leads but sill the same. If i only partially open the throttle i can get it right up through the rev range with no problem, but if at any stage i press hard on the gas it spits and farts and wont go. The engine light is on all the time now so im getting her on my mates vag com on friday see what it says. ill let ya know. I wonder if this is just some sort of limp home as of the sudden previons misfire though. Ive never experianced limp mode before on this car so i dont really know.

 

[mnadeem1984]

have you had your car chipped mate? Also is your wiring going towards the coilpacks all ok?

 

[J0E]

Yeah the car it chipped but ist been switched of for weeks so i dont think thats the problem. Ive checked all the wiring to the coils an it seams to be fine. Im kinda hoping when i put vag com on it and clear all the codes it will go away but i dont think it will.

 

[TheSpaceCowboy]

What you mean switched off?

 

[sonix]

Hey people,

I'm having exacty the same problem with my 1.8T TT engine.

Partial throttle no problem, but under full throttle, the engine starts stuttering and misfiring from the moment the boost comes up (2500 rpm, when you can hear the spin up of the turbo). The car has been chipped, but I don't think that has got something to do with it, as I had the same problem sometimes before, only much less, and only under maximum boost.

If I'm right a compressed gas mixture is harder to ignite, so I thought the ignition works fine under no boost, but with boost it shows somewhere its weakness.

JOE, did you manage to fix your problem already, seems I'm dealing with exactly the same thing.

on VAGCOM I get the misfiring codes, mainly on cilinder 3, but also had it once on 1 and 4. I'll swap the spark plugs/ignition coils and let you guys know if it worked.

cheers!

 

[[Dave B]]

I had similar problems, might be worth giving this a read: http://www.audi-sport.net/vb/showthread.php?t=44111

If that doesn't work it might be the ignition control module. IIRC these were present on earlier 1.8t engines and control the signals to each of the coilpacks. I think RichA3Turbo had this issue and reported it in a thread on here. A search may turn it up.

 

[sonix]

Thanks funkyjunky,

do you know untill which year they used this ignition control module? Mine is 2002, and I can't seem to find anywhere in the engine compartment.

I continued a little bit my troubleshooting, swapped the coils and spark plugs several times, and the misfire still seems to occur only on cylinder 4, and sometimes also on number 3.

Is the VAGCOM cylinder misfire detection reliable?

I was also thinking of a knock sensor problem, as it seems to work for each pair of cylinders. (1+2 and 3+4)

As this is a bifuel car, an interesting fact is also that the problem only occurs when working under LPG. The car is equipped with a sequential LPG injection system. I swapped the LPG injector valves around and the problem still remains.

As LPG is more difficult to ignite and under boost even more difficult, I was really thinking on an ignition problem (especially since these engines are quite prone to ignition problem as I'm reading). However very strange since I'm always having the problem on the same cylinder even after swapping coils/spark plugs.

Any suggestions are welcome,

thanks guys!

 

[[Dave B]]

Thanks funkyjunky,

do you know untill which year they used this ignition control module? Mine is 2002, and I can't seem to find anywhere in the engine compartment.

I think it's pre 2000 so I doubt this is your problem.

I continued a little bit my troubleshooting, swapped the coils and spark plugs several times, and the misfire still seems to occur only on cylinder 4, and sometimes also on number 3. Is the VAGCOM cylinder misfire detection reliable?.

I've found vagcom to be a bit hit and miss. In order to get the car to throw up a coilpack fault a had to give it some juice and force the engine managament light on.

I was also thinking of a knock sensor problem, as it seems to work for each pair of cylinders. (1+2 and 3+4)

I've had no experience with this but have heard it being a problem. Have a search on here.

As this is a bifuel car, an interesting fact is also that the problem only occurs when working under LPG. The car is equipped with a sequential LPG injection system. I swapped the LPG injector valves around and the problem still remains.

As LPG is more difficult to ignite and under boost even more difficult, I was really thinking on an ignition problem (especially since these engines are quite prone to ignition problem as I'm reading). However very strange since I'm always having the problem on the same cylinder even after swapping coils/spark plugs.

Any suggestions are welcome,

thanks guys!

Again, no experience with bifuel, sorry bud. Good luck with it.

 

[squale]

Hi,

Did you sorted if finally ? I got exactly the same prob..cant find the reason..

thx !