My car feels like it is misfiring

[VntEs]

Its a 90 Shadow Es Vnt (2.2 turbo IV).
At idle it feels like I have a misfire up to about 2000 rpm and then its fine. I don't feel it when I accelerate, or decelerate. While staying at a consistant rpm (like around 2000rpm) I can feel it but not as bad as when it is at idle. I pulled my spark plugs and all the gaps are good, no carbon build up. Did a compression check (155,150,145,145) and that seems fine. I checked and have no codes. My fuel pressure is 50psi if I just turn the key on, and 50psi when running. I rarely if ever drive it above 4000rpm. Its only done this the last two days or so which in northern IL we just had a warm snap (went from 30 to 70 degrees out) and wondering if that has something to do with it like a bad baro sensor. I also swapped in another hall effect pick-up just incase. I also heard about the distributor drive gear to the intermediate shaft sometimes strips out. I didn't have time to check that though. Just seeing if anyone has seen this before, or might know something else to check.

[BadAssPerformance]

I also heard about the distributor drive gear to the intermediate shaft sometimes strips out.

When Evan's intermediate shaft gears got loose in his CSX-VNT it idled ok but would not rev over 3500rpm. My old '87 CSX skipped a tooth on the shaft and ran perfect up until it did.

Any codes?

Could also be a loose shutter plate in the distributor? Bad ground somewhere?

[VntEs]

Yep Evan's, and that is what Dave was kind of thinking. My car revs fine. Shutter wheel on the distributor doesn't move on the shaft. It just sputters below 2k rpm. No faults. Funny thing is when it first starts and idles for about the first 10-20secs or so it idles smooth. Then it kind of sputters and you can almost hear a slight backfire in the exhaust. I even went under it when I got it home tonight to make sure the car convertor wasn't glowing red...........and it wasn't. I'm kinda wondering if I should drive it to work tomorrow cause on the way home tonight it just died out while I was coasting with it out of gear. It started right up after though. I did unhook the battery to see if I reset everything that would make a difference. It ran a little better, but still has a slight misfire/running rough. I also forgot that last night I did a throttle body cleaning just to see if that would make a difference. I changed the fuel filter about 2 years ago.

If the timing belt jumped a tooth that wouldn't cause this would it? I know around last fall, and last spring my car would act up kinda like this but never this bad. It would run rough for a little bit and then smooth out by the time I got home. It would do it for a week and then be fine. I wonder if it is rapid temp related (like due to our major temp changes lately).

[BadAssPerformance]

If the timing skips a tooth you know it... major power loss.

When my cars idle or run rough or anything like that I tend to beat the heck out of them a bit to see if they straighten out :)

[VntEs]

I do that and something major would break. :banghead: :banghead: Guess its telling me to get off my butt and buy a new car already. How much are them Srt8 Grand Cherokee's again? Oh wait I could afford the payment, but not the gas.

[BadAssPerformance]

Excatly, something breaks and thats how you find out what is wrong! ;)

SRT8 probably gets better gas mileage than my Dakota, LOL

[VntEs]

The Dakota gets worse then 10mpg? Ouch!!

[BadAssPerformance]

Best of 20 but lately more like 12...

[Turbodave]

Funny thing is when it first starts and idles for about the first 10-20secs or so it idles smooth.

Maybe it is a temp related problem, like a coolant temp sensor, O2 sensor or intake temp sensor. Maybe try driving it around with your scan tool hooked up and look at those to see if they seem right. If that doesn't work, you can borrow my Sun machine :D

[turbovanman²]

Whats your idle vacuum?

Condition and brand of coil and wires?

[VntEs]

Coil is a stock mopar one, that is about a year old. The wires are magnacore's and maybe 2 years old. There wasn't any build up on them at the distributor (checked when I swapped in a different hall effect.

I'm surprised the Sun machine doesn't have a flat panel playing Joe Dirt in it yet.

[VntEs]

idle vacuum was 20in/hg. The needle on my vacuum pump very slightly fluctuated.

While driving home I did my best to watch the scanner and try to remember some of the sensor readings. Coolant temp stayed pretty steady around 195 degrees F. Intake temp was around 120 degrees F. VSS was reading the same as the speedo. The O2 sensor also was doing the normal rich/lean switch between .2V-.9V. One thing that looked slightly suspect was there was a thing called AFF which I am guessing is my long term fuel trim. It was around -20 to -16.5 and would once in awhile go to +1.3. If that's the case, I can't remember if negative means the car is running rich or lean. If it means it is running rich then I probably got a vacuum leak/leaks that needed to be looked at and maybe that'll fix this nightmare.

[Turbodave]

Well, we found the problem on this one today, I stopped over at my cousin Chris' place (aka VntEs) and looked at the car, was not hitting on #3 cylinder, listened to the injector and it was working, pulled the plug wire and it was getting spark, pulled the plug and it was all wet, turned it around and a big chunk of porcelain was missing from it. Replaced the plug and it seemed to be back to normal again.

[VntEs]

Yep I have definately been working on German cars way to long. Thing is I have had that plug out a few times and didn't see it. So either it was just cracked before and finally broke, or I need to take a vacation from the kraut mobiles and remember to keep things simple.

[turbovanman²]

I hate it when that happens. It could have been cracked if you used a gapper and then push up the ground electrode to adjust the gap.