lt1 engine problems!

[69camarokid]

ok... so heres the problems and what i do know for sure.
95 trans am LT1/t56/
car will start up just fine, but idle very high. when the car is cold and just started it will shift from reverse or 1st gear back into nuetral and idle fine.... and geear after first back to nuetral the car will die. After its warmed up itll die even after first unless i continuously give it gas while braking with my other foot.

i know i have one bad O2 sensor... could that be causing the problem.
the car is ludicrously loud, but i think im hearing some backfire as well...

any idea what could be causeing all these problems... im at my wits end. i just want my camaro for the summer.

[paul67]

O2 you need to change as the comp is getting incorrect signals about fuel and air.

[Steve N 69 69 69]

Did you ever check/test/replace your IAC valve? Replacing that one part made a big differance on my car.
Check all over the intake manifold for any air (vacume ) leaks. mine ran like ***** with one of the holes unplugged.

[lt1chevelle]

Did you ever check/test/replace your IAC valve? Replacing that one part made a big differance on my car.
Check all over the intake manifold for any air (vacume ) leaks. mine ran like ***** with one of the holes unplugged.

+2 also if the motor you got was sitting a long time i would repalce all the sensors. MAP,IAC.TPS. i know it may not be cheap but it will narrow your problems down. also did you put new injectors in the car when you did the cam swap? i know they are probaly not needed unless you went with a good size cam but, maybe the injectors are clogged? i dunno im just throwing ideals out there.

[69LT1Nova]

Yeah, new O2, check your IAC valve. If that isn't it... your Optispark might have taken an Opticrap. If the car sits for a long time without being run, the rotor/cap will corrode, making your car impossible to run when warm.

[69camarokid]

Im ordering a replacement O2 sensor tonight.... so thats a start.

I checked the connections for my MAP sensor and IAC with my volt meter, both are good. I also cleaned the IAC. None fo thatmade any difference.

The car did sit for a while so that may have been a problem. After i change out the O2 sensor ill see how she runs and report back.

THANKS EVERYONE FOR THE ADVICE!!!!!
GREaTLY APPRICIATED!!!!

[81 trans-am]

You never said if it was giving you any trouble codes. You might want to find someone that can scan it for you. When I did my swap I had a bunch of weird problems. I had a leaking injector that caused a bunch of issues. My injectors where really gunked up and my setup only had 75k on it. Goodluck.

[WS6]

You also need to make sure you have a good amount of pipe after the O2 or it will still read incorrectly. This sounds like an closed loop issue which is typically O2 related since the O2 is not read by the computer until the computer goes into closed loop after the engine warms up.

[69camarokid]

my uncle works as a mechanic for the city, so he was able to borrow ascanner and scan my pcm for me. The only codes that come up was one for my MAP sensor, which had one cut wire, its fixed now. and another for theO2 sensor that was bad. the original one had gona bad, and my one aftermarket one was good.

but other than thise two the scan showed everything else to be working fine. The injectors were good.

[Nessumsar]

When the Opti in my caprice went south it would "surge", for a lack of a better term, on the freeway with cruise control. I dont know if you still have CC hooked up, but you could try that.

[WS6]

Get the MAP wire fixed and do the other stuff I recommended and see how the car runs then. I'm betting your problem will be fixed then.

[69camarokid]

cruise control isnt hooked up, so not too worried on that end.

As for the map sensor, i repaired that a few days ago, but it made no difference. I have an O2 sensor on order to replace the non working one. So thatll get here in a few days and hopefully thatll work.

if not then its time to take it too a shop and break in the ol' emergency credit card. ugh...

[Firebat]

The O2 is only used in closed loop mode. Closed loop happens when not in full throttle and happens when the car has been running for a couple minutes and when the temperature reaches about 140F degrees. If your trouble doesn't happen soon after you start the car then it could be the O2's. O2's will also go bad if they are put on new ceramic coated headers, the coating kills them, if the headers are used a little bit then should be fine.

Could also be a bad MAF. Just disconnect it before you start the car. If it still does the same thing then its not the MAF.

A bad MAP sensor caused backfire or loss of power for me. Had a good connection but bad sensor. Any GM 1-bar MAP sensor should work.

Sounds like a bad fuel filter or fuel pump though. Check fuel pressure. Check fuel pump regulator by taking off the vac line that runs to it and see if fuel is in it, then its bad.

Check everything else before you suspect the opti.

[firebird96ta]

Sounds like a bad fuel filter or fuel pump though. Check fuel pressure. Check fuel pump regulator by taking off the vac line that runs to it and see if fuel is in it, then its bad.


Agreed. Sounds similar to mine (but mine's all stock), which did the same thing when the fuel pump first started going bad (mine did run O2 codes and such then), and again when the EGR valve went. If it's backfiring, your SES light should blink (if you have one?). I would suggest finding someone with a Genesys or other similar scanner system to get real-time data (the guy I use only charges about $50) to see if all the sensors are working properly. There's been several times that thing has found the problem faster and cheaper than me throwing parts on the car. I've heard LT1's can be temperamental, and I know mine is.

I've got links to a couple great f-bod forums with good stock and modified tech stuff if you're interested.

Edited because: just saw your sig; this is in a '69? That's awesome. I'd love to hear it :)

[69camarokid]

The O2 is only used in closed loop mode. Closed loop happens when not in full throttle and happens when the car has been running for a couple minutes and when the temperature reaches about 140F degrees. If your trouble doesn't happen soon after you start the car then it could be the O2's. O2's will also go bad if they are put on new ceramic coated headers, the coating kills them, if the headers are used a little bit then should be fine.

Could also be a bad MAF. Just disconnect it before you start the car. If it still does the same thing then its not the MAF.

A bad MAP sensor caused backfire or loss of power for me. Had a good connection but bad sensor. Any GM 1-bar MAP sensor should work.

Sounds like a bad fuel filter or fuel pump though. Check fuel pressure. Check fuel pump regulator by taking off the vac line that runs to it and see if fuel is in it, then its bad.

Check everything else before you suspect the opti.

my headers are old and not ceramic coated so thats not an issue. The car idles fast ,around 850, when i first start it but wont idle after a minute or so, so a replacement 02 should help.

the MAP MAF both have good power, PCM connections, and grounds, so i dont think its them. But is it possible for them to be getting correct power and still not work?

the fuel pump is a brand new unit, and seems to work perfectly. and the vacuum plug behind the fuel filter had no gasoline that i could see, or shake out of it. how can i check/ pull out the fuel filter?

[Firebat]

You check the fuel filter and fuel pump by checking the fuel pressure, somewhere around 35-40 psi. MAF and MAP sensors can be shot even if they got the right voltage coming in and out of them. The only way I noticed my MAP sensor was bad was by hooking it up to a datamaster program through a laptop and then it was still hard to tell if it was giving correct MAP readings out.

I don't know how a fuel filter is set up on 1st gen camaros. If you got bad fuel pressure then replace that first. I wouldn't think it would run more than $15.

[69camarokid]

You check the fuel filter and fuel pump by checking the fuel pressure, somewhere around 35-40 psi. MAF and MAP sensors can be shot even if they got the right voltage coming in and out of them. The only way I noticed my MAP sensor was bad was by hooking it up to a datamaster program through a laptop and then it was still hard to tell if it was giving correct MAP readings out.

I don't know how a fuel filter is set up on 1st gen camaros. If you got bad fuel pressure then replace that first. I wouldn't think it would run more than $15.

ok, well i had checked the MAP and MAF sensors on a pcm scanner, not the little handheld one, but the big one that shops and cities use, it said only the MAP sensor wasnt working, but thats because it had no power. it does now.

how do i go about checking the fuel pressure. Im completely lost on that part. thanks!

[70 Chevelle]

Pop the mass air flow sensor out and remove the bolts holding the case together. You will see two bars that span the inner circumfrence of the tube. Look carefully at the filaments that span between the two bars, they look like diodes ,if they have exceesive carbon build up clean them. This problem compounds with a K&N filter as the oil in the filter tacks onto those areas and attracts all incoming objects. Use a q tip and electrical contact cleaner to clean them and be VERY delicate as they are fragile . Hope this helps.

[Firebat]

good point 70 Chevelle, forgot all about the K&N air filter oil on MAF problems.

69camarokid - here is a link for checking fuel pressure problems on LT1 - http://shbox.com/1/4th_gen_tech2.html#fuel_pressure_testing

Also, shbox.com is a good site for LT1 info.

[paul67]

The other thing to try as well is how much gas have you in the tank, i need a least 2 gallons for mine to run correct as i have not got a well for the pump to sit in.

[68Formula]

Optispark distributers are easily damaged due to moisture which tends to collect when the car has been sitting. I had similar symptoms on my '93 after bringing it out of hibernation. Car was fun to drive, but hating trying to work on it.

[paul67]

Did you get the problem sorted as I have same simtoms, I'm changing the O2 sensor as i found its only the left bank.