'84 Ignition/Timing Issue

[skoash]

Hello,
I have an ’84 Vette, with Cross-fire Ignition, that I’m having what appears to be ignition/timing trouble. It ran well earlier this year, but began having difficulty starting when the engine was warm. It was difficult starting when warm, and would run rough. Eventually this kept getting worse. The last time that I had it out, though, I made it out of my drive, but it died on the street. Each time I attempted to start it, the engine ran rough, and I would make it about 5ft, before it died. Needless to say, it took several minutes to get it back into the garage. I have since began diagnosing it, but am not having any luck. Like I said, once it was started it would run rough, and lots of backfire through the carbs. I have done the following to no avail:

1. Using an OBD-I tool, monitored the Check-Engine light, and found only Code-12 present (Normal).
2. Dropped the exhaust system ahead of the catalytic converter – no change
3. Replaced plugs, cap, rotor, ignition module, MAP – no change
4. Replaced fuel filter – no change
5. Checked fuel pressure, and it appears to be approx 9-13 lbs that it should be (according to the manual).
6. Set crankcase at TDC (at the timing mark), pulled the cap to ensure it was pointing to #1, pulled the valve cover to ensure both valves were closed, and made sure piston was at top – No change


I’m out of ideas. It sure appears to be timing. Any suggestions or other advice would be appreciated. Thank You!

Curt

[E Honda]

Originally Posted by skoash

Hello,
I have an ’84 Vette, with Cross-fire Ignition, that I’m having what appears to be ignition/timing trouble. It ran well earlier this year, but began having difficulty starting when the engine was warm. It was difficult starting when warm, and would run rough. Eventually this kept getting worse. The last time that I had it out, though, I made it out of my drive, but it died on the street. Each time I attempted to start it, the engine ran rough, and I would make it about 5ft, before it died. Needless to say, it took several minutes to get it back into the garage. I have since began diagnosing it, but am not having any luck. Like I said, once it was started it would run rough, and lots of backfire through the carbs. I have done the following to no avail:

1. Using an OBD-I tool, monitored the Check-Engine light, and found only Code-12 present (Normal).
2. Dropped the exhaust system ahead of the catalytic converter – no change
3. Replaced plugs, cap, rotor, ignition module, MAP – no change
4. Replaced fuel filter – no change
5. Checked fuel pressure, and it appears to be approx 9-13 lbs that it should be (according to the manual).
6. Set crankcase at TDC (at the timing mark), pulled the cap to ensure it was pointing to #1, pulled the valve cover to ensure both valves were closed, and made sure piston was at top – No change


I’m out of ideas. It sure appears to be timing. Any suggestions or other advice would be appreciated. Thank You!

Curt

I have an 85 that had the same issuses........It turned out to be the burn off module. On the 85 it is under the right hand side of the dash.

Be warned........if it has one......chevy no longer sells them and parts houses can't get them......And they are not cheap. around 900 clams quoted at the dealer. Just for them to tel me no longer available.

Hope this helps.

[Joe Wilson]

You could try a timing light to check for sure. Other things can cause a backfiring condition, a too rich or too lean fuel mixture can cause it. A compression tester would tell if your valves or pistons are damaged or if you have an intake valve that is too tight or cracked. If all else fails you can change it over to a carbureter and change the distributor to the old style, like a 1975 Chevy which pretty well takes the computer out of the equasion. Good luck
Joe

[Joe Wilson]

Originally Posted by Joe Wilson

You could try a timing light to check for sure. Other things can cause a backfiring condition, a too rich or too lean fuel mixture can cause it. A compression tester would tell if your valves or pistons are damaged or if you have an intake valve that is too tight or cracked. If all else fails you can change it over to a carbureter and change the distributor to the old style, like a 1975 Chevy which pretty well takes the computer out of the equasion. Good luck
Joe

You might check your fuel pressure at different times, like after the car has sat awhile. It's possible you have a fuel injector that is leaking fuel into the manifold, causing it to flood. That would make it backfire and die. The fuel pressure should be the same in the morning as it was when you shut the engine off hours before.