Miss once engine warmed up??

[blknt18]

I have a 94 z28 m6 that I have been trying to get running better. My factory pump was bad so I bought a walbro, it went bad, then I bought a factory one and has been fine since...knock on wood.. The car seems to run pretty good when I first start it up then after it warms up it will miss at high rpm sometimes during acceleration and also a miss at low rpm will cruising. I was planning on doing the plugs and wires but this whole once warm thing kinda gets me. Anyone got suggestions? Thanks.

[Fastbird]

What's your fuel pressure looking like?? How old is the coil?? Any access to a real time scanner or datalogger?

[blknt18]

Fuel pressure is fine I have checked it sooooo many times. Old coil and no scanner or logger. I did go to autozone awhile back and got the egr code. I unplugged the vacuum to that but that shouldn't be it.

[IronOutlaw]

Burnt plug wire.

[Fixxer99TA]

Does the car run bad intermittantly when warm? Or just crappy all the time as soon as it gets warm?

If its intermittant while warm (periods of crappy running for a minute, then fine for 10) then it sounds to be your O2s. Check all your plug wires though, always start with the cheap crap and easy stuff first.

[Fastbird]

If you unplugged the vacuum to the EGR, then you've got a vacuum leak. Try sealing that off and see what happens.

[blknt18]

I have played with the egr line and it still acts the same. Was planning on doing plugs and wires first. I think it usually runs bad once warm then all the time while warm. I took it out the other day and went on the highway and it ran great on acceleration but when I drive around town then take it out it will miss.

[hempkat94z]

sounds like you are running a little rich....I would say o2s are starting to fail. I had a similiar problem great on the highway and at WOT but stoplight to stoplight it would miss and stumble leaving the light

[lt170chevelle]

i would have to agree with the o2 sensor going bad. . they only come into play when it warms up and goes into closed loop mode.

[BLK95TA]

my vote goes to one of the plug wires being damaged/disconnected/etc..

i had this same problem and i thought it was the opti so a friend told me we should change the cap and rotor. we got the waterpump off and look at the cap and one of the plug wires was barely connected to it. since it had 106k on it we changed the cap anyway but the fact it was loose was the problem

[kinglt1]

Yea sounds like bad o2's!

[Tyler Wheat]

I'd change the plugs/wires and see where that gets you.

Alot of guys have problems with the opti after the temp gets up to par. I've ran into that a couple of times. If the plugs/wires don't do it for you, I'd be checking into the opti.

This is assuming there is no SES light and the fuel pressure is up to par.

[BLK95TA]

FWIW on mine i knew it wasnt the plugs/wires as they only had 10k mi on them or so (MSD red wires and NGK iridium plugs)

[blknt18]

So I got 2 o2s for 60 bucks shipped total. They were afs 75s so they are the good and right ones. I replaced the driver side and still have the pass. to do because I need an extension to remove the starter. Also sometimes I will be cruising along the interstate and the car will just jerk, like a big miss. I also believe it is running bad at idle so maybe not just once warm.

[blknt18]

http://photos-a.ak.fbcdn.net/photos-ak-sf2p/v356/188/13/16916007/n16916007_38172568_3806.jpghttp://photos-g.ak.fbcdn.net/photos-ak-sf2p/v356/188/13/16916007/n16916007_38172566_3194.jpg

[blknt18]

So my throttle body was wayyy dirty this is after I cleaned it a bit. It was full of oily crap. I was thinking maybe from the valve cover breather?? Also here is one of my plugs. I don't think it looks that bad. It has some crap along the bottom edge but the electrode looked ok I thought. Also they are ac delco, the dealership I bought it from put them in like 5 months ago.

[joelster]

Another one for the O2's. It will run normal for about say 2-3 minutes then *WHAM* instantly runs different when it goes into closed loop.

[blknt18]

Well I got the drivers side done but that pass side sucks...gonna pull starter sat and get the other sensor changed out. Any one have a clue why the throttle body is so dirty?? Should I put a stand alone breather on the valve cover and plug the hole on the throttle body?

[IronOutlaw]

Was your car throwing a code? If not my money is still on plug wires, which it could very well be the o2s. I just hate to see people throw parts at a car like i did when i put my headers in and had a miss. (3 sets of o2s, new MAF, new coil, and then i replaced the plug wires with 28 dollar oreilly wires and bam, my miss went away completly.)

[blknt18]

it was throwing the egr...I unplugged the vacuum hose to it now but it runs the same with it connected. The egr is closed though. I pushed it in and it ran worse so I don't think that should have anything to do with it.

[blknt18]

I checked my icm at AZ and it checked out good. I checked my coil and it showed 7000 ohms at each slot and shoebox said around 8000 or 8500. Idk if that means mine is low or if it is just that...they all read the same though. I also did the icm cooling mod while I had it all apart. I am trying to remove the pass. o2 sensor and having problems... I removed the starter but can't get it past the stock y pipe so I just slide it out of the way but I cant get the the sensor very well because the stupid joint to the manifold is in the way. I kinda get to it but the thing is on so tight. Hopefully I can get it later. I still think it is the opti because wires look great.