tricky1090

I recently started getting really bad stuttering / vibrating when accelerating. It feels rough (more virbration than normal) when idle, and really bad as soon as you start accelerating. CEL came on and I took to mechanic who read cylinder 4 & 5 misfires. He said he switched the coilpacks and the misfires didn't follow, and the spark plugs were leaking voltage. For some reason, it actually drove fine back from the mechanic, no noticable vibration. I changed out the sparkplugs for NGK Laser Platinum (#6458), and now it's misfiring worse than before. Code now simply reads Random misfires. When I looked at the old spark plugs, they seem to be gapped around 0.040...seems like they should be 0.028 - 0.032 (depending on which thread you read). Can the 'gap' get bigger the more worn a spark plug is? The new ones come pregapped 0.032. I checked them all and they're closer to 0.030. Can a cylinder misfire if the gap is too close? I visually checked the MAF and it's clear. Anyone have any other suggestions

tricky1090

I changed the coolant temp sensor and no different. Still misfiring.

AFC__B5S4

I am having the same exact issues, my mechanic got no codes for misfires, so it is going back in tomorrow for another look. Hopefully I can get it all sorted out. It was 'misfiring/bucking' normally, now it is only under acceleration. I never even got any CEL or engine lights to come on.

I cleaned the MAF, seafoamed, re checked the plugs (gapped at .032), and checked around the engine for any lose parts.

If I figure it out I will be sure to let you know.

tricky1090

I'm either getting P0300 (random misfire), or I get Cylinder 5 misfire. I've switched coil and plug from cylinder 5 but still get one of these 2 codes. I guess I'll look at fuel injector or ICM next.

tricky1090

Switched the ICM's and the code jumped to Cylinder 2. Time for a new ICM then. Other thing is a really strong sulphur smell from the exhaust. Could this be caused by the misfire? REALLY hoping my cat isn't shot

tricky1090

So I switched the ICM out and it's fixed the misfires. Then today I got code P1131 which I believe is O2 sensor related. I cleared it and it hasn't come back yet. Could this be related to the misfires I was experiencing, or running rich at the time?

Chris's S4

I've had a random misfire though very faint, I got chipped couple weeks ago, and this weekend decided to take out the plug and clean and measure gap... well they were all WELL above .28, more like .40 so I put em at .28, cleaned them. Reinstalled and had vag com up and runnng, the moment it fired up, I had all kinds of rpms jumping around, misfires like crazy.. like more than 30 in a cycle. mostly in cylinder 6. So I switched ic's around, it jumped to cylinder 2 and the rest as well as before, also did coilpacks.

So I found out I need new icm's and coilpacks... I did switch from stock to 91 performance on the chip and did notice a massive change in misfires.... seriously huge. Stock not so many, still there... chipped, whole bunch... and crazy fast too.

Oh well, it's better to change them out that way they're wont cause anymore problems. I did notice that cleaning the plugs made all the misfires way more obvious. completely.

Chris

EuroXS4

yes 02 sensor faults could be related to the misfires because the unburned fuel was getting dumped into the exhaust and could have ruined the 02 sensor and possibly the cat.Seen it before.

Chris's S4

I've got Bank 1 02 sensor that comes up now and then... My rears have stopped since I've added plug defoulers. Ahh.. amazing lil tools. But still probably bad rear 02's... not that they're important or anything, so meh.... Now the fronts, yes, they control fuel mixture, so I'll be replacing those two for now hope that'll work out.

As for you, probably would be a good idea to replace the front 02's also. Sometimes it's for the best, even if it's not bad.



I think I killed my bank 1 02 by unplugging it while the engine was running, then plugging it back in. Never had an issue with it till after some time I did that. So I think I may have killed it that way. Oops. sigh.... more money now.. crap. lol

EuroXS4

nah unplugging it while running shouldnt cause it to fail.I know in vag com there is a measure value block to look up the voltage readings on all 4 02 sensors. I dont remember what the number is but thats one way to check it.if you got 0v then you know the sensor is dead because the 02 generate voltage or put out a voltage between .3-1.0volts.if it below .3 then you know it shot.