fcat8187

when the car starts up it runs fine idles fine heats up and runs really rough and doesnt want to accelerate at all but once it gets up to 2000rpms smooths out and runs ok not great but ok was having this problem put in a new opti and still doing it deosnt make sense to me at all... i just put in cam,rr,honeycome valve springs, new rocker studs, and new bearings,LTs
and im running open exhaust now
any suggestions would be great this motor is making me really angry!!

Flores96TA

Man that is a LT1 with some problems, but everyone has them. You sound like you know engines and how to install parts so why dont you start with some simple stuff. I would start right from the source of the problem cooling. Lt1's (Camaro Firebirds TRans Am any F body the factory elec fan switch is set about 225or so I have heard . Check some things like
1. R the Fans coming on
2.with all that new stuff did you change your thermostat(couple of bucks to 160)
3.Coolant change make sure new coolant not some stuff in a drain pan left over from rebuild.
4.check engine light on run a on board computer check(free at auto zone service light must be on
But it has to do with coolant

Low N Slow

iTrader: (4)

I had bad plug wires and my car ran just like yours. Also ignition control module can act up from heat.

streetwarrior96

radiator might be dirty, might need a flush, should install a fan switch. Make sure there is no debris between the radiator and the condensor. 160 Thermostat.
One time my car sucked up a plastic bag right on the radiator and fucked my world up.

~JOSHUA

iTrader: (92)

It might be that you have a lot of sediment in the fuel tank. When you drive around it sloshes and get's picked up. Try changing the fuel filter, if it gets any better at all you should remove the fuel tank and flush it. The LT1 cars have metal tanks instead of the plastic ones in LS1 cars. Sediment and internal rust WILL happen.

thesoundandthefury

iTrader: (3)

What year is your car? Sounds like a bad oxygen sensor. If your car is a 93-95 model it has 2 O2's and if it's 96-up it has 4. Reason I say I think it's an O2 problem is because you say that when you first start the car up it idles fine until it heats up. The PCM actually ignores input from the O2's until the AIR pump has had enough time to heat them up to a preset operating range. So during that time the PCM is not making fuel corrections based on that input, which is why it'll idle properly. When the O2's DO get to operating range and the PCM starts making calculations based on their input, if the O2's are bad they will give the PCM false readings and throw off the fuel map. GM designed the O2's so that in the event that they should fail, the input they send the PCM will report a lean condition. This will cause the PCM to up the fuel percentage and make the engine run pig rich.

The second clue you gave that makes me think O2's are the problem is you said when you rev it up the engine seems to run better momentarily. The reason for this is that during WOT, the PCM switches back to open loop and once again ignores input from the O2's. Since by revving up the motor you're constantly fluctuating between open and closed loop, the O2's explain the engine running good some of the time and bad the rest.

You can test which of your O2's (or all) are bad by unplugging them all and letting your car idle for about 8-10 minutes till it's fully warmed up, then plugging each O2 back in successively until you find which one is making the car idle poorly.

Hope that helps.

bandit95

mine did the same thing and it was bad wires and opti at first, then it started again and i fixed the o2's and that fixed it.

fcat8187

ok so i just took the car out and it ran poor from the start up on its OK at higher rpms 2000+ but a dog down low i have put in new o2s already opti and wires and plugs(this is why i am sooo frustrated) by the way the car is a 94... i do think the o2s make a lot of sense though and i am really suspect of the ignition control module because that is the only thing that hasnt been replaced do those normally go bad slowly? and progressively? and if it is fuel i gonna be ****** PIST i hate dealing with dropping tanks and stuff... oh yea and correct me if im wrong the fuel pumps are in the gas tank right?
i have an obdII scanner and i came up with an EGR code erased the computer drove it around and didnt come back on i had a bad vacuum leak and i fixed that... i think i might try the o2 test since i had to extend them for the LTs i might have messed up and then the ignition control module anyone know what those run ya?

fcat8187

ok so the icm didnt help anything