Eman_clp

Fellow enthusiasts,
I posted this originally on the CL forums but the TL section seems more active so I thought I'd throw it up here and hopefully get more eyes on it.
Original post and video are here
https://acurazine.com/forums/2g-cl-2...-cl-p-1000839/

In short, the engine is sluggish, there's a rumbling/shudder when idling under load, and a puffing sound (maybe coughing?) during cold idle. No visible air leaks and all sensors are reading correctly according to my scanner. Upstream O2 seems high at 0.6V during idle, but the sensor is ok. All mounts replaced except for the rear. There appears to be oil on the spark plug tips, which may or may not be from before replacing the VC gasket - giving it some time to see if that persists after the fix. No misfire codes reported though.

My next step was to clean the intake manifold and inspect the IAC - other than that I'm not sure what else to check. Someone on the CL side suggested to check the cat so I'll be doing that today or tomorrow.

Any other thoughts? I'm open to all suggestions.

whitetiger5

Have you checked the ignition coils? I had a problem once, it went like this:

1. Car had an occasional rough idle, kinda like the engine puffing a little more air than usual from time to time and a roughness when in gear and stopped (engine is more connected to chassis) but no CEL, so I let it go...
2. The rough idle soon generated a CEL for misfire on 6,1,4 cylinders
3. Upon inspection, found the spark plug in cylinder 1 came loose (this cylinder is in the far back, and because of lack of access I always errored on the side of caution/loose when replacing plugs) resulting in compression loss and certain misfiring.
4. This fouled up the that plug, tube and coil; proactively replaced that pug and coil as well.
5. rough idle was still present...
6. replace remaining coils
7. rough idle was still present...
8. did a valve clearance adjustment
9. rough idle was still present...
10. replaced new coils one by one with one of many old coils I still had...
11. rough idle went away!
12. returned the new defective coil to rock auto.

Jon M

Do you have the short term fuel trim reading? This can help verify fuel injectors are operating properly.

Eman_clp

Interestingly, I was searching youtube today to see how to adjust the valves. I do have a brand new coil that I inexplicably bought last month, I'm gonna try it in different cylinders to see if anything changes. I'll report back soon.

Can't remember which bank, but one of them was high the last time I checked. IIRC it bounced around 8-12%, but mostly was on the high side. Long term was 4.7% and I think 6.8% but I'll do a second run as soon as I can.

Eman_clp

Also, follow up question whitetiger5: about how long did it go on before you got the misfire codes?

whitetiger5

I had two problems. The loose plug resulted in a misfire; probably immediately.

Once that was fixed, the bad could never gave me a misfire (months); just that very random rough idle that is even hard to define as that; because most of the time we associate rough idle with a continuous, consistent variation in the idle speed.

what I experienced was just an occasional puff coming from the exhaust when the car was parked and idling, a shake when looking at the engine when it's idling and if in drive and at a stop (like waiting at a red light) the shake could be felt in the car; similar to when the AC cycles on/off but obviously I had the AC off...

Eman_clp

That sounds like what I'm seeing - mine goes away after it warms up though, but it's a loud puffing noise. I did try the coil swap and there wasn't a noticeable difference in any of the cylinders so I went ahead and cleaned the throttle body and IAC. Both were actually very clean already though. I also noticed the oil was very low, maybe from leaking into the cylinders, so I topped it off. I got a VCG kit on the way and will be doing that hopefully this week. Oddly my trans fluid was also very low but there are no signs of leakage anywhere, haven't been driving it so I'm not too worried at this time.

The good news though: I swapped the rear mount and the shaking is completely gone. The engine is much smoother and quieter in all conditions. The idle still bounces around a little bit but it's drastically improved now. I can't believe one mount can cause this much vibration.

Anyway, next steps are VCG, EGR valve, new plugs, then oil change and tranny drain/fill. I'll report back here once it's all completed.

thanks again for the help whitetiger5