Misfire questions

[h4rb]

04 B5.5 AWM 1.8T FWD

I have noticed that when I watch measuring blocks 15 and 16 (misfire counters) that I seem to have a small number of misfires. Is this normal? Also seems strange but when I give it constant throttle and rev it a little it does not seem to register any misfires. I just monitored it for about 5 minutes and registered approx 15-20 misfires total.

1. Why do they only show up at very low rpm / idle?
2. Are a low number of misfires at idle normal?
3. Are any misfires normal at idle?
4. Should tapping the throttle at idle create misfires?

I have replaced 2 of my coils due to the common issue related when they fail. That had the flashing MIL symptom, rough idle etc.. After replacing the bad coils I've never had that symptom "flashing MIL" ever again, nor was the idle ever even close to that bad. Lately I have noticed that while idling it would occasionally misfire, nothing near previously but misfire nonetheless.

I had just replaced my plugs w brand new decent NGKs prior to my coils going nutz and being replaced. Did they nuke my plugs too???

Please LMK if I have left out any needed details.

[h4rb]

BTW, VAG shows no misfire codes stored. Yet I can watch them occur via blocks 15 and 16. ???

[Steve in Chicago]

Are there any other trouble codes showing up? You shouldn't be getting misfires like you describe. What are your plugs gaped at? Are the misfires across all the cylinders or only specific cylinders?

[jlefty]

Out on a limb here but might help. I have the 2.8 but they have there similarities. Mine only misfired at idle to then got much more noticeable come to find out my drivers Cam chain tensioner was failing so timing was inconsistent. Which lead to failure of the plastic chain guide and a loud ticking and so she sits till I gather parts. Like I said might help good luck.

BAM

[h4rb]

Car has sat awhile (2 months) due to various reasons. I ordered new plugs and new coils despite the existing ones being relatively new just to be sure that I rule out these 2 components. I now get misfires only on cylinder #3 at idle, no flashing MIL. Idle seems fine, does not get rough, I replaced the plug and the coil with brand new VW coil and NGK plug. Cylinder 3 still shows misfire under measuring block 15. Kinda stumped on this one. Ill run the report again and see if any new codes are available.

[ajshoe]

did u find a solution to this misfire problem ??? I have a 2001 1.8T awm auto passat with rebuilt engine. My symptoms are it runs perfect until the engine idles a long period (engine warm - leave car on and return and the engine is running rough). misfiring ?? and giving it gas will increase rpms but runs rough. If I turn off engine and restart - runs perfect again. Can drive it anywhere and it runs perfect. Stop car and put it into park - leave car and return and it sometimes will be running rough. Code it throws is misfiring on cylinder 2 and 3. Has new iridium plugs, new maf, new battery, new coil packs (swap them - same error). fuel pressure is 50 psi, doesn't leak anything, everything on car works like new. anyone have a suggestion ???
UPDATE: seems that only goes into misfiring mode when put in park, leave car, return and it is running rough. Only way to get it run correctly is restarting engine.

[the_abuse]

I had the same problem the most common cause is vacuum leaks (somtimes bad MAF). I deleted my PCV system to get ridd of all the vacuum lines and also deleted my SRI injector pumps and i haven't had a misfire since. (previous to this i had them daily on start up or after the car came to a stop to idle after driving for a while.) I ordered the SRI block off plate and aluminum crankcase breather adapter from 034 Motorsport. and ran it to a vented catch can. ( be warned that vented catch cans arent needed unless your going to be running a big turbo and high boost. i should have just ran a sealed can because i have been getting some pretty wicked smells and when i warm up my car in the morning for work i gotta leave my hood open so the fumes dont go in the car. but i will be making a re route for fresh air for the cabin filter intake . i have also read of people connecting a line to their down pipe to cause suction to the catch can while the car is idleing. but besides that. Since removing the catch can I have noticed alot better response from the cars turbo and DV. Also this job WILL take you the whole day and you should have a lift because you will have to go under the car and back to the top a bunch of times and order silicone vacuum line to replace what line you need to keep because it lasts forever and streatches when hooking stuff up

[BobbyShaftoe]

I chased a similar issue this winter. Re-building my PCV system finally solved it.

[atsffan]

did u find a solution to this misfire problem ??? I have a 2001 1.8T awm auto passat with rebuilt engine. My symptoms are it runs perfect until the engine idles a long period (engine warm - leave car on and return and the engine is running rough). misfiring ?? and giving it gas will increase rpms but runs rough. If I turn off engine and restart - runs perfect again. Can drive it anywhere and it runs perfect. Stop car and put it into park - leave car and return and it sometimes will be running rough. Code it throws is misfiring on cylinder 2 and 3. Has new iridium plugs, new maf, new battery, new coil packs (swap them - same error). fuel pressure is 50 psi, doesn't leak anything, everything on car works like new. anyone have a suggestion ???
UPDATE: seems that only goes into misfiring mode when put in park, leave car, return and it is running rough. Only way to get it run correctly is restarting engine.

Highly suggest you install the OEM plugs - usually the NGK's. They run about $10 each, but the 1.8T is so picky about plugs - there's lots of threads here about people trying other brands & models and the end result is that nothing works quite like the OEM plug. The last set I installed on my 2000 1.8T were NGK PFR6Q - labeled "Laser Platinum".