I have a 90 Iroc w/350 TPI motor. After rebuilding the tranny I noticed there was a miss. The number 8 plug was carbon fouled after replacing it about 1500 miles earlier. So I replaced it and it seemed to run great for the first 5 minutes then it went back to missing again. I pulled it and it was carbon fouled again after 10 min of driving. What causes that to happen? It is also idling high, 1200-1500 RPMs....that because of the fouled plug? What do u guys think? Thanks

 

Sounds like a bad wire?? Is it sitting too close to a manifold?

 

Wires look good no burns from the headers. They are MSD wires..not very old either.

 

Number 8 injector might be leaking.

 

Right before the tranny went out I replaced all the injectors so I didn't get to drive it very much on the new ones. Would I be able to see the fuel leaking out around the injector

 

"Carbon fouling" tells me nothing. There is fuel fouling, and there is oil fouling. A plug can also be sooted from too rich AFR. However, a sooted plug will not generally misfire. You lost #8 cylinder after only 5 minutes running. This means that either the plug is being fuel fouled or oil fouled. Was the plug wet with oil or with gas? If its wet with gas(it will smell like gas and dry fairly quickly), you probably have a leaking injector.

No, you wont be able to see the pintle leaking unless you hold the rail out of the manifold while its pressurized. Unless you have the injector locks in place for this, they will be pushed out of the rail by the pressure.

If the plug is wet with oil, you probably have a broken ring. You can buy some time by installing an antifouling insert on that cylinder but you will be in for a rebuild.

 

No oil deposits it is a dry soot. I can swap the injector to another slot and see if it does the same thing. If it is leaking does it need to be replaced or can it be fixed?

 

Okay. Black dry soot I recognize. Its almost certainly the new injector you just installed. Were they new or reman? Ive had this happen a few times with reman and once with cheapo Delphi injectors. I do not know of any way to cure it. Its either a pintle valve thats misaligned or a bad seat. Either way the injector has to come out. Your supplier should have no problem exchanging it. Its not that uncommon.

Btw, I do not advise moving the injector and continuing to run the engine. That injector is dumping raw fuel into your motor and on to you cat. A new cat will only add to the cost of this repair. Just swap out the bad injector and go on.

 

These were new Venom injectors I installed. I'm having them send me a replacement. Would the bad injector cause it to idle high though?

 

It's possible. There may be another issue but you can't really do anything until the current issue is fixed.

 

Does anyone know what the correct resistance is for good injector?

 

12-16 ohms and all within an ohm or so.

 

How bad is it for the motor when the injector is leaking?? I haven't drove it since I suspected a bad injector but I did drive it for a couple of days before that.

 

If you drove the car in a normal manner, not thrashing it, it shouldn't have done any harm. Ive had numerous vehicles come to me with one or more cylinders being overfueled. They all have gone away fine after the fueling issue was repaired. You will want to change your oil since its likely been contaminated with excess fuel.

The single leaking injector may cause your ECM to pull fuel trims way low trying to solve a rich condition. This will cause the other cylinders to run lean which can in turn cause a high and uneven idle. Replace the bad injector and see if the engine doesnt return to normal operation.

 

I'm getting close to getting the Camaro fired back up. I'm guessing since there was soot all over the plug that it's all over the piston head and cylinder. Should put in any additive to get that cleaned up...Z-max, Lucas??

 

A good fuel treatment such as Chevron Techron or B-12 Chemtool should work fine. Or just run good fuel that already has the additives in it.

 

Ok here is what I got...I replaced the injector and the fouled plug. It is still idling between 1400-1500 rpm's. What else would cause a high idle like that. As soon as I pull it in gear it drops to normal.

 

Does it go back up when you take it out of gear? The TC will pull the idle down to around 700-800 RPM or so if its stock as it loads the engine.

 

It goes back up to around 1500 RPMs as soon as u take it out of gear.

 

Sounds like it could be something like a vacuum leak, mis-set min air at the TB, or a faulty IAC

 

I forgot to mention I found a cut wire on the #5 injector electrical plug. Fixed it but its still idling high in park or neutral...in gear it's normal...go back to park and it's idling high again. Any ideas?

 

When you take your foot off the brake in drive, does the car surge forward, or does it creep like it normally would in drive?

 

There's no surge or anything...it does feel like I have to hold the brAke down a little harder to keep the car from moving. But it doesn't jump or anything..just feels like it has more torque at idle...best way to put it I guess.

 

try pulling your vac line off your fpr, and maybe smell the line for fuel, or just key up engine off to see if fuel comes out of fpr, my diaphram went bad and hydrolocked motor

 

Sounds like a vacuum leak, or throttle hanging open, or possibly an issue ith the IAC. Those would be the most likely things to check. As for the vacuum leak, it would most likely be in the upper plenum or near the TB. Vacuum leaks at the intake base just cause ind. cylinders to go lean. Vacuum leaks further up act like opening the throttle, and giving the engine more air.

 

Let me ask this I have a IAC valve from a 90 corvette, same motor. Autozone says it should be the same as the 90 Camaro. Will it work in my 90 Camaro?