89 Corvette runs rough wont start when warm!

[aristolimo1]

Hi all, new to the forums, but I do have a question to ask some of the gurus here who may be able to help since the local Chevy dealership seems clueless. My 1989 Corvette will start every morning when it is cold run like a champ, but when it gets to operating tempature, it will idle very rough when in gear at a stop light, etc. The rpm's go down to 600, and it just seems like it wants to stall, but wont. Then when I park it and shut off the motor then try to restart, the engine has an extended crank but will not turn over to start! I have to wait for the engine to cool a bit before it will start.
I have had the plugs, wires, fuel filter, cap, rotor, air cleaner, pcv changed. fuel injectors serviced, and the ECM REPLACED! Still it exhibits the same problem as when I brought it to them the first time, now I am a thousand dollars lighter in my pocket, and no answers! ANYONE! Please help me here with a solution!. The fuel pressure is at 40 lbs, the spark is there, all is there that is supposed to be to turn it over but it will not. I read a similar thread about this and I think "vettefreak" mentioned there was a TSB about the MAF relays, I did mention that to the tech at the dealership, but he blurted something about when you have the Bosch system which mine does it wont affect it?
Anyone might know a solution would be praised very highly!

 

[SSTibet]

I replaced all three O2 sensors of my 95 LT-1 and resolved a similar problem like yours. I do not know how many sensors your Vette has; most probably 2 - one after each cat.

Here is some theory:

The engine starts operating in "open loop" mode when it is cold. The engine switches to "closed loop" mode after the engine exhaust gas reaches a certain temperature. The oxygen sensors take control at that stage and starts sending signals to the ECM for "rich / lean" condition based on the amount of oxygen in the exhaust gas they measure. ECM regulates the "on-time" of the fuel injectors based on the signal from these sensors. The engine can stall at low rpm's (such as at traffic lights) and when accellerating from a stop if the sensors are defective. They are inexpensive parts readily available even in Turkey, where I live. My advice is to replace them all.

That's what happened to my car... Hope it helps.

Cheers,

Selim

 

[aristolimo1]

Thanks, I may have to go that route, since I just called the dealership and they just changed the MAF relays and it is still exhibiting the same problem! I am about to lose my mind here, I hope this helps! Anyone else?

 

[SSTibet]

Aristo,

When this problem happened in my car I took it to my mechanic who does not have the diagnostic scanning tool. He insisted that it would not happen from the O2 sensors:confused . So we cleaned some of the valves (EGR, IAC, etc.) only and the problem did not go awayad .

Then I went to another shop who has the scanner . I am sure there is a repair shop around you with one of these tools. He scanned the engine and told me almost immediately that passanger side O2 sensor was "lazy"... In the sensor was not generating the signal as it should. We decided to change all 3 of them. And Bingo, no more problem since that day

Are you getting an error code in your DIC? I was getting one of those. If that is the case the same scanner can retrieve the code and tell you what's wrong right away. The error codes need some interpretation though before jumping to a conclusion. In either case - with or without the error code - I would get the engine scanned first...

Cheers,

Selim

 

[vigman]

Try this

I assume when you " start" you do not have your foot on the throttle.. right?

next time hold you foot in it to the floor....this tells the ECM to clear a flooded engine.... see if that gets it.. it does on my 88 I have a similar problem from leaky injectors.. after the car sits for a bit it floods due to injector dribble in the cylinders.

The 2nd question is when she is HOT ( assuming car off ) have a buddy listen in the fuel tank ( cap off ) and turn the key to ON you SHOULD hear a 2 second burst of the pump priming the engine.. see if that works too!

Vig~

 

[tomd]

My 92 was exhibiting the same symtoms. I could also smell raw gas fumes when the engine was warm. I decided to replace both o2 sensors and all is well.

 

[89ZZ4]

Your 89 has one O2 sensor on the drivers side. Replace it if it's got over 30K miles on it.

 

[aristolimo1]

Ok here is the story so far, the dealershop has now changed the fuel pump and the fuel pump regulator, both MAF sensor relays and all the other things I have mentioned prior. Now they are saying they are as baffled as I am and that they have over 1000 dollars into the work and parts and they have one more option to test the fuel injectors seems they checked with someone who said the injectors are touchy and it could be the problem if they arent signaling correctly or some such nonsense. If that is the problem, they said parts will run over 1200 dollars and that doesnt include labor, if not... now get this, they will give me the car back and tell me they can't fix it! I asked if they checked the o2 sensors and the service guy yes'd me on that but I don't know if the tech did or not!
So a Chevy dealership can't fix the car why doesnt that suprise me, I am just disgusted with it all, I don't know where to turn next. By the way thanks so far for the answers to everyone!

 

[aristolimo1]

Ok the Chevy dealer gave up on my car after installing a new fuel pump and regulator, Now I have it at another place where the guy I do know says he can fix it. He says the pulses on the fuel injectors are very weak, and thinks it has to do with an aftermarket alarm system that was in the car when I bought it. It might have a start interupt and perhaps the box that controls the alarm is biting the dust! Oh good God just get rid of the thing! I told him to take it out and hopefully I will get some good word on it today!
So who thinks I should write to GM and explain to them all the money I had already spent on this vehicle (in excess of $1500 dollars) and the dealership never fxed my problem? Secondly does anyone know where or whom I would write this type of letter too?

 

[JimVette]

Good luck trying to get a refund from GM. If it is not under warranty they basically wash their hands. To them it is a used car and all this is between you and the dealership. I hate to say this because I have always been a Chevy fan but there are very few dealerships that have knowledgable mechanics that can work on older Corvettes. In it's money saving efforts GM did away with the specialists the dealerships could call to get help. No longer are they able to call the plant and talk to the likes of a Gordon Killebrew and get it right the first time. They just remove and replace until it fixes the problem. Did you get the parts they replaced. There was obviously nothing wrong with them.

 

[Robertwav1]

Good luck trying to get a refund from GM. If it is not under warranty they basically wash their hands. To them it is a used car and all this is between you and the dealership. I hate to say this because I have always been a Chevy fan but there are very few dealerships that have knowledgable mechanics that can work on older Corvettes. In it's money saving efforts GM did away with the specialists the dealerships could call to get help. No longer are they able to call the plant and talk to the likes of a Gordon Killebrew and get it right the first time. They just remove and replace until it fixes the problem. Did you get the parts they replaced. There was obviously nothing wrong with them.

You are sooo.... right about the "knowledgable mechanics" thing. I guess this is the reason we are having trouble flying a space shuttle like we once did. All the tech people are gone.....cutbacks....wonder what this is gonna cost in the grand scheme of things??? Will industry ever figure this out? The consumer is paying dearly....such as in this case....totally unfair! Get your parts back! Don't go back there or recommend them to anyone.

 

[laurie1]

Hi all, new to the forums, but I do have a question to ask some of the gurus here who may be able to help since the local Chevy dealership seems clueless. My 1989 Corvette will start every morning when it is cold run like a champ, but when it gets to operating tempature, it will idle very rough when in gear at a stop light, etc. The rpm's go down to 600, and it just seems like it wants to stall, but wont. Then when I park it and shut off the motor then try to restart, the engine has an extended crank but will not turn over to start! I have to wait for the engine to cool a bit before it will start.
I have had the plugs, wires, fuel filter, cap, rotor, air cleaner, pcv changed. fuel injectors serviced, and the ECM REPLACED! Still it exhibits the same problem as when I brought it to them the first time, now I am a thousand dollars lighter in my pocket, and no answers! ANYONE! Please help me here with a solution!. The fuel pressure is at 40 lbs, the spark is there, all is there that is supposed to be to turn it over but it will not. I read a similar thread about this and I think "vettefreak" mentioned there was a TSB about the MAF relays, I did mention that to the tech at the dealership, but he blurted something about when you have the Bosch system which mine does it wont affect it?
Anyone might know a solution would be praised very highly!

Hi a new member here, Hope I'm doing this correctly, here goes
I have an 89 with a very similar problem.
On warm days, 80F or so, my car does the same thing, starts good when cold, after driving in traffic for awhile, then shutting it off, and leaving it for a half hour or so, try to re-start, it will crank and fire, then immediately die, while still cranking? Will not stay going! This has being going on for a few years now, and NO CODES are being set. By opening the hood and let it cool for 10 mins or so, then try again, usually will start up OK.
So, what I just discovered the other day is, to "unplug the MAF sensor" try starting the car, which it does start, let the idle settle down, takes 40 secs or so, shut it off, reconnect the MAF sensor, re-start the car. This has worked in my case, everytime. To me this points to the Maf as the problem, BUT, I'm not 100% sure, so I'm still trying different things, as maf sensors up here in Canada are $780 (new acdelco) so I want to be 100% sure, not the old "try this try that" process, as you have found out in your experiences!
I'm not sure if this will help, at least it doesn't cost anything!!
I also have tried to find the problem using Datamaster and scaning the car,
No error codes are showing up BUT, I'm still trying to learn how to read the data file?

 

[aristolimo1]

Ok so here is where I stand seems three of the fuel injectors are not all that great on the car even though there is only 42000 miles on her the resistance is twice what they should be. The extended crank seems to have something to do with this and the fuel injector fuse was blown! Imagine that a nickle part and they could not figure it out! I am going to have the three injectors changed and I will let you know if it fixed the problem, this is what a mechanic i at least trust is telling me now anyway.

 

[tigmaned]

so how did it turn out for you? did you do all eight injectors since they had the pelnum off.

 

[laurie1]

You posted to the wrong guy

so how did it turn out for you? did you do all eight injectors since they had the pelnum off.

Hi there. I may have messed up this thread, I suggested do the check of your MAF sensor by unpluging it.
Will I'm here, I need to know which brand of MAF sensor you all have found to be a good replacement, besides the ACDELCO, which are sooo expensive up here in the Great White North. The price spread is huge $250-$780
Actually the car runs very good with out the MAF , makes me wonder??
Like to hear from anybody who has tried a few different Maf sensors. Are they all the same? Thanks for any help here!