soccaz34

I have an AP1 car, 135k miles. I did a engine compression test the other day, everything looked good, 220, 220, 230 230 psi across cylinders. After done I drove some errands and the car started misfiring very noticeably. Next day, I disconnected everything again and did compression test with a different gauge, same results. Reconnected everything and I've had the misfire ever since. It happens only below 2k rpm and idle and more when it the engine is cold. For example if it starts to misfire at a stop light I can raise the rpm with throttle to about 1.7-2k. rpm and misfire goes away. When the engine is really warmed up and heat soaked (some highway drive) it almost goes away completely. The worst part is though...THERE ARE NO ENGINE CODES. I don't even know which cylinder is misfiring.The engine definitely "chokes" when the misfire happens and it can be felt in the cabin.

I don't want to start throwing money at this, so maybe someone can help out here.

Car Analogy

Why are you certain its misfires? Could it be some other issue that causes rough idling?

Like a dirty idle air control valve or a vacuum leak?

windhund116

Any chance of bad fuel?

yourboysoap

Had this same exact issue. Only bogged close to idle and on acceleration, no codes. Cleaned IACV and checked all electrical, all good.

Ended up being one of my ignition coils was failing. Once I located the problematic one, I could tell there was an arc pattern on the rubber so something wasnt connecting properly. A new one solved my issue.

soccaz34

I also bogs on acceleration. I solved all my idle issues already with the car prior to this started happening

Car Analogy

That didn't answer the question. What makes you certain the symptoms you are experiencing are actually misfires? That may help with diagnosis.

soccaz34

When the engine “bogs” it’s when an individual cylinder “misfires” and it doesn’t produce torque for a single piston power stroke. Very sudden, also has an exhaust pop associated it with. Also when a few happen in a row my AFR gauge reads higher that 14.7.

windhund116

Just to be sure, you've ruled-out bad gasoline?

Thanks!

HarryD

+1 for yourboysoap and the case of the bad coil pack

Here's my thread -- symptoms were a slight misfire, pops out of the exhaust, no CEL:
https://www.s2ki.com/forums/s2000-un...-idle-1130073/

Here's a video of my symptoms:
https://www.youtube.com/watch?v=0Uvr...ature=youtu.be

One new coil pack fixed it -- buy one, and swap it from cylinder to cylinder until your symptoms disappear.

outeiroj

next time you start the car unplug each coil momentarily one at a time and then reconnect. if its a misfire you should be able to pinpoint which cylinder is causing it because the misfiring cylinder will misfire less when unplugged. coils are a very common cause of misfires and if you still have the original coils it may be worth investing in a set of 06+ coils