Tweet
For those of you who helped me with my "slow crank" thread, thank you. This is a different problem. The slow crank problem was just a semi-dead 9-yr old battery. The problem started after a LIM & head gasket repair, and it has been resolved with a new battery.
THIS issue is a totally different animal. It has been a chronic problem ever since I bought the car over 3 years ago. Here is the background saga:
Purchased the car around 2004, it's a 1998 Monte Carlo 3.1 L. It had around 50k mi on it. Within days of purchasing the car, it started experiencing hard starting. It would crank strong, but longer than it should before firing up. I would also get intermittent misfires, on different cylinders. If I put the car in neutral and revved the motor hard, the misfire would go a way, temporarily. Maybe for a day or so.
Eventually the misfiring and hard starting got worse to the point I knew it needed some mechanical repair. Took it into the dealer it was purchased from, and they cleaned the injectors. Told us these cars are notorious for gummed up injectors. They physically removed the fuel rail and rail solvent through the injectors on a machine to clean them and observe the spray pattern. They said 2 of them were spraying in a poor pattern, but after cleaning were good. This seemed to improve things for a few weeks, but then the hard start and misfires returned.
I am quite mechanically inclined, so I decided to try and tackle the problem myself. Started with a simple plug and wire change. It made no difference at all. I tested the coils, and found one bad one, so I replaced it. This took care of the misfire problem, and I haven't had a misfire since then (about 2 years). The stupid hard start issue just wouldn't go away though, and keep getting worse and worse. It got to the point that you HAD to give the car gas while cranking it, otherwise it would fire up and immediately die. You had to pump the gas pedal like a carbeurated car, and get the revs to like 2-3 for a few seconds after startup so it didn't choke out. Once it was running, it was fine, ran normal like a champ. It's just the startup that was problematic.
Figuring maybe the fuel injectors were gummed up again (it had been like 10k), or maybe they were just bad and the dealer was too cheap to replace them for me, I decided to get ALL NEW injectors. I installed a full set of brand new injectors, but sure enough it made no difference.
I then started hunting electric/sensor stuff. Replaced the IAC valve figuring maybe it was letting too much/little air in during crank. No change. Replaced PCV, and hunted for vacuum leaks. Still the same. Tried running different brand and grade gas, no difference.
I read about the problems on these motors with the LIM gaskets, and sometimes headgaskets. I was getting some milkywhite junk on my radiator cap, and oily deposits in the coolant resevoir tank, so I knew I had a problem. Tore down the motor all the way to the pistons. Both LIM gakets were bad, typical crack around the coolant passages. The head gaskets seemed perfectly fine, but while I was that far in the engine I figured I would replace them just incase. Two of the spark plugs looked totally nasty with corrosive deposits. I assume this was coolant leaking into the combustion chamber through the intake runners (failed LIM seal), getting baked onto the electrodes of the plugs. I had an "ah-ha" moment, and thought for sure this was the cause all along of the hard start problem. I figured after I put in all new top end gaskets and got the motor running that the hard start problem would go away. I put in new AC Delco platinum plugs and fired her up. It starts SOOO much better when it's a cold start now. Turns over fast, fires up, stays running. But it's the warm/hot starts that are still really really bad. Cranks forever, catches, and then just dies. Gotta rev the gas to keep it going for a few seconds after crank. Then it runs fine.
At this point, I've replaced just about everything I can think of. To me, the only logical thing left in my mind is that there is too much ignition advance during crank when it is hot. I know in the ECM timing advance tables, there is a crank advance map which specifies different degrees of advance depending upon coolant temp. But I don't understand why this would be off, as it is a stock ECM.
Has anybody ever experienced a problem like this before? Gone through the depth of diagnostics and repairs as I have? WHAT IS THE SOLUTION?
Thanks,
Jacob
THIS issue is a totally different animal. It has been a chronic problem ever since I bought the car over 3 years ago. Here is the background saga:
Purchased the car around 2004, it's a 1998 Monte Carlo 3.1 L. It had around 50k mi on it. Within days of purchasing the car, it started experiencing hard starting. It would crank strong, but longer than it should before firing up. I would also get intermittent misfires, on different cylinders. If I put the car in neutral and revved the motor hard, the misfire would go a way, temporarily. Maybe for a day or so.
Eventually the misfiring and hard starting got worse to the point I knew it needed some mechanical repair. Took it into the dealer it was purchased from, and they cleaned the injectors. Told us these cars are notorious for gummed up injectors. They physically removed the fuel rail and rail solvent through the injectors on a machine to clean them and observe the spray pattern. They said 2 of them were spraying in a poor pattern, but after cleaning were good. This seemed to improve things for a few weeks, but then the hard start and misfires returned.
I am quite mechanically inclined, so I decided to try and tackle the problem myself. Started with a simple plug and wire change. It made no difference at all. I tested the coils, and found one bad one, so I replaced it. This took care of the misfire problem, and I haven't had a misfire since then (about 2 years). The stupid hard start issue just wouldn't go away though, and keep getting worse and worse. It got to the point that you HAD to give the car gas while cranking it, otherwise it would fire up and immediately die. You had to pump the gas pedal like a carbeurated car, and get the revs to like 2-3 for a few seconds after startup so it didn't choke out. Once it was running, it was fine, ran normal like a champ. It's just the startup that was problematic.
Figuring maybe the fuel injectors were gummed up again (it had been like 10k), or maybe they were just bad and the dealer was too cheap to replace them for me, I decided to get ALL NEW injectors. I installed a full set of brand new injectors, but sure enough it made no difference.
I then started hunting electric/sensor stuff. Replaced the IAC valve figuring maybe it was letting too much/little air in during crank. No change. Replaced PCV, and hunted for vacuum leaks. Still the same. Tried running different brand and grade gas, no difference.
I read about the problems on these motors with the LIM gaskets, and sometimes headgaskets. I was getting some milkywhite junk on my radiator cap, and oily deposits in the coolant resevoir tank, so I knew I had a problem. Tore down the motor all the way to the pistons. Both LIM gakets were bad, typical crack around the coolant passages. The head gaskets seemed perfectly fine, but while I was that far in the engine I figured I would replace them just incase. Two of the spark plugs looked totally nasty with corrosive deposits. I assume this was coolant leaking into the combustion chamber through the intake runners (failed LIM seal), getting baked onto the electrodes of the plugs. I had an "ah-ha" moment, and thought for sure this was the cause all along of the hard start problem. I figured after I put in all new top end gaskets and got the motor running that the hard start problem would go away. I put in new AC Delco platinum plugs and fired her up. It starts SOOO much better when it's a cold start now. Turns over fast, fires up, stays running. But it's the warm/hot starts that are still really really bad. Cranks forever, catches, and then just dies. Gotta rev the gas to keep it going for a few seconds after crank. Then it runs fine.
At this point, I've replaced just about everything I can think of. To me, the only logical thing left in my mind is that there is too much ignition advance during crank when it is hot. I know in the ECM timing advance tables, there is a crank advance map which specifies different degrees of advance depending upon coolant temp. But I don't understand why this would be off, as it is a stock ECM.
Has anybody ever experienced a problem like this before? Gone through the depth of diagnostics and repairs as I have? WHAT IS THE SOLUTION?
Thanks,
Jacob
Comment