very rough start, then improves after ~20seconds
05-20-2004, 01:55 PM
#1
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very rough start, then improves after ~20seconds
95 lt1 ta, very very hard to start. It starts and then stalls immediately. After that it wont even start unless i wait. Then I need to give gas to get it started and I need to hold the gas down for about 20 seconds or so while the car goes "chug chug chug". Then it smoothens out and its fine... until I shut if off and its time to start it again. Idle is a bit rougher when i stop at the lights too, but that might just be me imagining things (heads + mild cam, stock tune)
This problem started yesterday when i put gas in the car. Any help would be appreciated. Its hard to reach a dealer or mechanic cuz im working when they are open and im off when they close
thx
This problem started yesterday when i put gas in the car. Any help would be appreciated. Its hard to reach a dealer or mechanic cuz im working when they are open and im off when they close
thx
Last edited by med_reject; 05-20-2004 at 06:36 PM.
05-20-2004, 06:54 PM
#2
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Location: Mishawaka, IN
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You know, my car had this problem a while back, I'd hold the gas pedal down and it would run really rough, and then all of a sudden it would run just fine. I think it was something in my ignition, the switch or possibly a loose wire, once I replaced those the problem hasn't come back. It was really wierd though, it would only do it every once in a while.
05-20-2004, 07:01 PM
#4
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Dunno. All I remember is that I replaced the ignition switch, which involved taking apart everything in there, and then cleaning any of the wire connections under the hood I could get my hands on. I'm not positive on that though, it could have been something else. You might want to go over all the basic stuff first and make sure nothing is out of place or loose.
If it starts up all nasty try turning the car off and starting again and see what it does. These cars are a pita to diagnose. They should offer degrees in "What the hell is wrong with my LT1" mechanics.
If it starts up all nasty try turning the car off and starting again and see what it does. These cars are a pita to diagnose. They should offer degrees in "What the hell is wrong with my LT1" mechanics.
05-26-2004, 09:29 PM
#5
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changed the ignition lock and cylinder, that didnt help. now the car is throwing a code (good thing, unless the rough starts screwed up a sensor), its harder to start up (almost impossible).
I gave it to the dealership. I'll let u guys know what they find, if anybody has ideas, i'd like to hear them.
I gave it to the dealership. I'll let u guys know what they find, if anybody has ideas, i'd like to hear them.
05-26-2004, 09:34 PM
#6
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Almost sounds like what happens when I sprayed the fuel soelonoid with the car off to test my nitrous system. IT took a long time to start, then it just chugged on up till it burned the extra fuel off.
06-28-2004, 04:29 PM
#8
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1 month later...
finally got an opticrap, installed it, car still doesnt want to start. Dealer spend 2hrs doing all kinds of diagnostics and they say that the pcm is not sending a proper signal to the injectors so that needs to be replaced.
If that does not fix the problem, i cant return the pcm, so i figured i'll get 1 from madz
I had a hard time believing the pcm, with no moving parts, could fail like that. I'll keep everyone updated incase another unfortunate soul has to go through this. Meanwhile any other ideas would be greatly appreciated.
finally got an opticrap, installed it, car still doesnt want to start. Dealer spend 2hrs doing all kinds of diagnostics and they say that the pcm is not sending a proper signal to the injectors so that needs to be replaced.
If that does not fix the problem, i cant return the pcm, so i figured i'll get 1 from madz
I had a hard time believing the pcm, with no moving parts, could fail like that. I'll keep everyone updated incase another unfortunate soul has to go through this. Meanwhile any other ideas would be greatly appreciated.
06-28-2004, 09:14 PM
#10
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If it were the Vehicle Anti-Theft System, the security light would be steady or blinking. Doubt that's it since it only comes in when cranking not after it starts.
Don't think it's the PCM since the same brilliant MFers said it was the opti.
It sounds like you have a fuel problem. Long cranking times are usually from fuel draining back toward the tank or fuel dripping into the intake and puddling. In either event, the fuel pressure at the fuel rail will drop off very quickly after the engine is shut off.
First check for any fuel leaks near the fuel rails and particularly around the FPR. Then pull the vac line off the FPR and see if it's wet. I would also put a vacuum source like a mityvac brake bleeder on the hose to see if it holds vacuum. If not replace it.
Now eliminate the injectors as the cause. 2 ways to do that. You could pinch the plastic line before the fuel rails on the incoming side, as you shut down the car. If the pressure still bleeds off, the injectors are the problem. I don't like this method though because you could damage the plastic lines if you're not careful.
The other way to check the injectors for leaking is to lift the fuel rails and injectors up so the nozzles are visible and turn the pump on. There is a fuel pump prime connector located near the PCM. With pressure, the leaky one(s) will be visible.
If you have eliminated the injectors and the FPR as the cause of the quick fuel pressure drop after the car is shut down. The only thing left is the fuel pump. The problem would be a sticky check ball in the stock pump.
Don't think it's the PCM since the same brilliant MFers said it was the opti.
It sounds like you have a fuel problem. Long cranking times are usually from fuel draining back toward the tank or fuel dripping into the intake and puddling. In either event, the fuel pressure at the fuel rail will drop off very quickly after the engine is shut off.
First check for any fuel leaks near the fuel rails and particularly around the FPR. Then pull the vac line off the FPR and see if it's wet. I would also put a vacuum source like a mityvac brake bleeder on the hose to see if it holds vacuum. If not replace it.
Now eliminate the injectors as the cause. 2 ways to do that. You could pinch the plastic line before the fuel rails on the incoming side, as you shut down the car. If the pressure still bleeds off, the injectors are the problem. I don't like this method though because you could damage the plastic lines if you're not careful.
The other way to check the injectors for leaking is to lift the fuel rails and injectors up so the nozzles are visible and turn the pump on. There is a fuel pump prime connector located near the PCM. With pressure, the leaky one(s) will be visible.
If you have eliminated the injectors and the FPR as the cause of the quick fuel pressure drop after the car is shut down. The only thing left is the fuel pump. The problem would be a sticky check ball in the stock pump.
06-28-2004, 11:36 PM
#11
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i was told that the fuel pressure was fine (By canadian tire and the gm dealership), but i did not ask them if it maintains the pressure after the car is turned off. I tried started the car immediately after shutting it off and it still cranked and cranked.
They'll prob tell me that the fuel injectors are not getting a signal, which is why they think its the pcm.
I'll ask if they checked for fuel pressure drop after the car was shut off.
Thanx for the help man, that was very informative.
They'll prob tell me that the fuel injectors are not getting a signal, which is why they think its the pcm.
I'll ask if they checked for fuel pressure drop after the car was shut off.
Thanx for the help man, that was very informative.
06-29-2004, 05:20 AM
#12
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If injectors were not getting the signal to fire causing it to not start easy, then why would it start at all 
Any simple $10.00 noid light would tell them of that.
If an injector were not firing, the cylinder would be dead. You could read the exhaust manifold temperature with an infrared thermometer or even a squirt bottle of water and find the dead cylinder.
I've seen ignition problems causing long cranking and even dirty injectors that don't put out enough fuel until they crank for a while.
Sounds like to me you need to get away from these rocket scientists. If you did, it would probably save you some money to boot.
Any simple $10.00 noid light would tell them of that.
If an injector were not firing, the cylinder would be dead. You could read the exhaust manifold temperature with an infrared thermometer or even a squirt bottle of water and find the dead cylinder.
I've seen ignition problems causing long cranking and even dirty injectors that don't put out enough fuel until they crank for a while.
Sounds like to me you need to get away from these rocket scientists. If you did, it would probably save you some money to boot.
06-29-2004, 04:36 PM
#13
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I spoke with those guys today.
They said the car held fuel pressure for 10mins after it was shut off (43psi), and that the noid light indicated the fuel injectors were nto getting any impulse. They said that now the car wont start at all.
They did a bunch of checks (wiggle test and wires etc.) and said the whole system is working fine, which leaves the pcm. I'll let u know if that does the trick... i wanted tuning anyway.
They said the car held fuel pressure for 10mins after it was shut off (43psi), and that the noid light indicated the fuel injectors were nto getting any impulse. They said that now the car wont start at all.
They did a bunch of checks (wiggle test and wires etc.) and said the whole system is working fine, which leaves the pcm. I'll let u know if that does the trick... i wanted tuning anyway.
06-29-2004, 04:45 PM
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06-29-2004, 06:44 PM
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If your injectors are not getting the right signal it could be the PCM. Does the car "kinda" try and start or is it just straight whirring by the starter motor. If its kinda trying to start it could also be the wiring harness not talking with an injector or 2... Maybe it got damaged or something. I would imagine they could easily test for that though, so theyre probably right that its the PCM.