Misfire at idle

Synned · Jan 22, 2006

My car has a misfire at idle and i can feel it when im driving around 2k rpms in first gear. The car will vibrate pretty bad when im idleing, but only sometimes. I have cleaned the MAF, new plug wires and plugs, new ECT and new o2's and fuel filter. (They were not all changed because of this problem).
I'm going outside to run a cylinder balance test.

Could this miss be related at all to detonation? My car pings on the highway pretty badly, like above 65. It used to do it from 35 but I put in 93 and 108 octane booster.
It doesn't seem like they both could be related, but I hope so.
Thanks guys.

95cobraguy · Jan 22, 2006

i would say the first step is to isolate the exact cylinder that's missing, and then take it from there.

CManT1914 · Jan 22, 2006

Bad vibrations at idle, bad pinging all the time, sounds kind of like your balancer. Whacked timing can have some weird effects. Check your balancer, make sure it's not on it's way out.

Synned · Jan 22, 2006

Okay, ill look at my balancer.

But I think it's a miss not the balancer thats causing the vibrations because the rpms drop a little it surges.
Today I did a cylinder balance test as well as KOER and the only code I got was
116 or something Coolant Sensor out of range.
This is a new ECT. Could it be bad? I know that coudl cause my detonation, but nothing about the miss. I also passed my cylinder balance test, but thats because the miss is at idle not at 1800 rpms where it tests.
I also pulled out all the plugs, re-gapped them and checked all the wires were down good. And re-cleaned the MAF. Still have a bad idle miss, not sure about detonation.

CManT1914 · Jan 22, 2006

Check the balancer, just because it's real easy to check, and they go out quite frequently.

FWIW, I would think that a miss caused by bad plugs, wires, low compression, whatever, would be present at any rpm, and not just at idle. But I've been wrong before.

Synned · Jan 22, 2006

CManT1914 said:
Check the balancer, just because it's real easy to check, and they go out quite frequently.

FWIW, I would think that a miss caused by bad plugs, wires, low compression, whatever, would be present at any rpm, and not just at idle. But I've been wrong before.

Yeah, me too. It might even be at all rpms, but either I don't notice it or it's not there. But at idle its very noticable and rpms drop and surge.
What I did notice when I was just inspecting the car is that the distributer cap has some play. Like I can tilt it back and forth. It's clamped down on both sides, so I dunno what the deal is.

Where else could the miss come from?

Thanks for the help guys.

CManT1914 · Jan 22, 2006

Inside the bowl, there are two screws that hold the bowl to the base of the distributor. Check to make sure those are tight. One of mine was loose, and the bowl would rock back and forth, even though the cap was tight, and it was causing some funny issues. Just pop the cap off and make sure those screws are tight.

Synned · Jan 22, 2006

Yeah I'll check that, though its the top cap that wiggles a little it wouldn't hurt to try.

I kinda looked around for a vaccuum leak and didn't find any. Could that ECT sensor cause it to be lean and detonate?

CManT1914 · Jan 22, 2006

Oh the way you said it, I thought you meant your whole bowl was loose.

The ECT does effect a/f ratio. For instance, on cold startups, the ECT senses the engine is cold, so the PCM delivers more fuel to help startup. So yea, if the ECT is bad, then it could be causing you to run lean.

Synned · Jan 22, 2006

CManT1914 said:
Oh the way you said it, I thought you meant your whole bowl was loose.

The ECT does effect a/f ratio. For instance, on cold startups, the ECT senses the engine is cold, so the PCM delivers more fuel to help startup. So yea, if the ECT is bad, then it could be causing you to run lean.

Okay I'm going to try a new ECT to try to eliminate the pinging. The detonation is the priority problem.

How bad is it if occassionally the car pings for 5 seconds? How long do I have before I blow some **** up?

I can live with a misfire a little, but everytime my car pings I cringe.

Synned · Jan 22, 2006

I read somewhere that a misfire at idle is a "lean misfire"

Maybe they are connected! Pinging and misfiring.
I didn't know that a misfire could be cause by a lean condition... I dunnol.

95GTV8 · Jan 22, 2006

well, to help counter the pinging turn your timing down from 14 to 10?

Synned · Jan 22, 2006

95GTV8 said:
well, to help counter the pinging turn your timing down from 14 to 10?

Yeah I have

Synned · Jan 22, 2006

This gasket actually looks like its missing right here.

So somehow my car is running lean causeing both of these problems. The lean misfire and the WOT preignition.

Synned · Jan 22, 2006

woops..double post
so ttt!

Synned · Jan 22, 2006

This might sound really stupid but my wires arent like separated. They all run together and probably cross a lot of times. Could this cause a lot of problems? I should go buy those things...to separate them.

HISSIN50 · Jan 22, 2006

You can do the 'spray water on the wires' trick and see if they are bleeding spark.

The EGR gasket is very thing - metal-like. I am not sure you would see it with the EGR bolted up. It takes about 2 mins to unbolt the EGR, so go for it if you want (two nuts/bolts, the feed pipe - soak that in PB first, and a vac line. That is all I recall doing).

I posted more on your other thread.

Good luck.

CManT1914 · Jan 22, 2006

I doubt your wires are cross-firing. They come tied together from the factory, so that's not usually an issue. I'd also do that water thing (much easier to see at night by the way), to see if maybe your spark is jumping.

Synned · Jan 22, 2006

Do you guys think that the faulty ECT sensor could cause my lean misfire? It could also cause the pinging I guess.

I'll try that tomorrow, just buy a cheapey pep-boys.

Synned · Jan 26, 2006

Okay well the ECT sensor did nothing for me.

I was wondering, if the PCV valve has not been changed in a while, it could be related to detonation right?

Misfire at idle

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