So i rebuilt my bottom end. Went .30 over and got a cc503 cam. This is in a 95 firebird formula. The first day and a half was great...breaking it in..would get into it slightly some, not much though just enough. It was running great. Then yesterday mornin after it runnin for a few minutes drove it and it had a little miss to it. Smoke was coming from the farthest back driver side fuel injector. Pretty much just loosened everything and tried to push it further in. After that it ran fine and hasnt done that since. Well then last night i was driving and it started running bad again but no smoke this time. Once the car actually cut off coming to a stop light. All of today it has done nothing but got worse. It misses and stutters all of the time with at some points almost no power. Just reving it hesitates but not no where as bad as if under a load. Earlier it threw a few backfires while accelerating. Im pretty sure i have a vacuum leak from the evac box i believe its called (the black box on the passenger side of the intake) to the throttle body and i may have one from the hose that plugs into underneath the opti. But it doesnt seem like that would make it run as terrible as it has been. And no where around here can scan my car since its a 95. It does it in open and closed loop. So could it still be an O2 sensor? I dont understand how it was running fine then all of a sudden its horrible. Any ideas?

 

When I installed new plug wires one got burned on the headers. It took a few days to get bad and then it would idle and drive like it was missing a cylinder. It sounds like something was burnt from the smoke you described. Find that and you might have your solution. You should add a signature with everything you have done to the car.

 

I dont really understand why is was smoking though. It was coming out of where the injector plugs into it. But its only done it once then never done it again. My wires appear to be fine...

 

it also seems to run a little rich but i dunno. should i try replacing the fuel filter?

 

i just now went out and started it up. sitting there running it would backfire from the exhaust. it doesnt run to bad just sitting but under a load it is terrible..

 

readjusted the valves. ran it. didnt run any better. started to smoke from the injector again so i pulled it out completely and there was no gasket. replaced the gasket and it seems to run a little better..but not much. and there is a strong smell of gas from under the hood..any ideas??????

 

Are you saying there was on O-ring missing from the injector? Which one - top or bottom? If you were missing the bottom O-ring, you had a huge vacuum leak on that cylinder. That causes the entire bank to run excessively rich, because the O2 sensor see all the extra air from the vacuum leak. Running it long enough its was probably fouling the plugs on that bank. You need to check them. Running it that way long enough can damage the rings when the excess fuel washes the oil off the cylinder walls. Check your oil for gasoline dilution.

If it was the upper O-ring, you'd have fuel all over the engine.

Might want to check all the injectors for top and bottom O-rings. After you get the injectors out of the intake manifold and the rails, make sure the O-ring is not stuck in the manifold or the rail. Then check the plugs, and check the oil.

 

replaced all of the o-rings. there wasnt one on the bottom of the number 7 injector. and it wasnt stuck in the intake either. so i guess my next bet is to check the plug..appreciate the help!

 

Check ALL the plugs on the driver's side. When you have all that excess air blowing out the exhaust valve, it causes the other three cylinders on that bank to run pig rich.

Check the oil for a strong gas smell.

Seriously.

 

park your car in the dark and look under the hood for wires arching

pull the plugs and check for which ones look fouled/lean

hook up a vacuum gauge

doesn't sound like o2 problem imo

 

alright well ill be checkin the plugs and oil here in a little bit. appreciate the help so far

 

the oil had a hint of a gas smell to it but it wasnt extremely strong i dont believe. but say it did damage the rings...any way to fix it if it isnt bad without havin to pull my motor..again?

 

not really could be cylinder wash down from excessive rich condition ,damaged rings, etc. is there any metal flakes in your oil?

 

there doesnt seem to be any flakes in it..could tell you 100% but i sure dont see any. it does have a hint of a gas smell to it..the motor has less than 200 miles on it..just got it runnin less than a week ago

 

I would change the plugs, put in new oil and fire it up to see how it runs.. But I am not an expert