Thump then misfires

[Rajini98]

Driving along, I had a sudden thump after acceleration. The thump felt almost like I hit a pothole (it wasn't an actual pothole I hit). Parked to do some grocery shopping and when I got back in the car, everything ran fine but as soon as I accelerated out of the parking lot, I had bad misfires on cylinders 2 & 3 all the way home.

I've let the car sit for a while as well as cleared the fault codes but the misfires on cylinder 3 remain even at idle. I'm going to check on the basics tomorrow when there's light out like plugs and coilpacks. If the misfires remain in the same cylinder, then I'll know its either a compression, fuel, or injector issue.

How likely is it that this is a compression issue? I can deal with pulling the intake to change out injectors(and clean the valves while I'm in there) but a blown piston ring or head gasket is way outside my comfort zone.

I did search but didnt see any threads that involved a random misfire that started a recurring misfire.

 

[Rajini98]

Just ran it a while and it now only misfires intermittently. Going to let it sit overnight then top it off with some ethanol free premium nearby and take it for a long drive tomorrow.

Still confused about the cause though.

 

[Rus.K]

Sounds like it could be bad coil packs have you checked those lately

 

[Bake]

could the pop have been an exhaust backfire?

 

[Rajini98]

could the pop have been an exhaust backfire?

It might have been. It was dark out so I couldnt tell if I left a cloud of smoke behind me.

Sounds like it could be bad coil packs have you checked those lately

Last time I checked them was when I had them replaced back in early 2011 for the recall. I'll test them tomorrow to see if the plugs or coilpacks are the problem. I changed the sparkplugs around 30k miles ago. They could be on their way out.

Just took it for a decently long run and the misfires only occur on cylinder 3 but consistently. When coasting to a stop, the engine runs normally (since the injectors turn off) but when accelerating, especially in the low RPMs, the misfires are very noticeable.

 

[Rus.K]

It might have been. It was dark out so I couldnt tell if I left a cloud of smoke behind me.



Last time I checked them was when I had them replaced back in early 2011 for the recall. I'll test them tomorrow to see if the plugs or coilpacks are the problem. I changed the sparkplugs around 30k miles ago. They could be on their way out.

Just took it for a decently long run and the misfires only occur on cylinder 3 but consistently. When coasting to a stop, the engine runs normally (since the injectors turn off) but when accelerating, especially in the low RPMs, the misfires are very noticeable.

If I'm not mistaken cylinder 3 is gonna always be the first one to miss fire first. It sounds like sparks or coils to me

 

[Rajini98]

If sparkplugs, I might as well order a whole new set of iridiums. I just hope that the Autozone nearby has sparkplugs that will work in the mean time. This is all of course assuming that the sparkplug in cylinder 3 is the problem. If coils, i'll have to limp my way to the nearest VW dealer an hour away. If injector...I'm kind of screwed but it is what it is.

Edit: searching for similar problems in general so it includes other car brands and years, spark plugs are the solution 99% of the time. I'll provide an update tomorrow if spark plugs fix it or if the coil is the problem. I can probably get a compression test at a local mechanic shop to rule that out in the event the spark plugs/coils arent the problem.

 

[majorahole]

If sparkplugs, I might as well order a whole new set of iridiums. I just hope that the Autozone nearby has sparkplugs that will work in the mean time. This is all of course assuming that the sparkplug in cylinder 3 is the problem. If coils, i'll have to limp my way to the nearest VW dealer an hour away. If injector...I'm kind of screwed but it is what it is.

Edit: searching for similar problems in general so it includes other car brands and years, spark plugs are the solution 99% of the time. I'll provide an update tomorrow if spark plugs fix it or if the coil is the problem. I can probably get a compression test at a local mechanic shop to rule that out in the event the spark plugs/coils arent the problem.

if it doesnt miss all the time, its probably not the compression.

 

[Rajini98]

Swapped plugs and good as new. I'm a little concerned that there's so much white buildup on 1, 2, and 4 but that could be because I'm running the one step colder NGKs other threads have recommended. In the pics, you can see that 3 was definitely the problem.

 

[majorahole]

white isn't from heat range. if you do a run on brand new plugs and kill it at the top of the rpm's, then pull the plugs, you will see the discoloration on the ground strap. if its the correct heat range it should be about halfway down the ground strap.
just a lil plug tuning fyi