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Discussion Starter · #1 · (Edited)
Hi there, I have a 86 El Camino 4.3L. Everything is stock. I've been having this problem for quite sometime but it stumbles off the line, warm or cold. I was getting a MAP Sensor trouble code so I replaced the MAP sensor. The distributor cap, rotor, wires, and plugs looked worn so I replaced those as well. The stumble problem immediately improved but the problem persists. Before I replaced these components it would stumble hard and often but since replacing these parts, the engine continues to stumble but its noticeably less. If I creap the accelerator peddle up slowly it decreases the number of occurences and more cases than not, doesn't stumble. What's weird is it doesn't stumble when reving the engine in park, only when accelerating either in drive or reverse.

I thought it could be the ignition coil or the oxygen sensor so I replaced those and while the engine runs considerably smoother, it continues to stumble. Since I cleared the MAP sensor trouble code, I'm not getting a diagnostic code from the computer. I recently replaced the fuel pump and fuel filter and the PSI from the fuel pump is normal. I looked for a vacuum leak but couldn't find one. The ElCo is kind of new to me so I tried to locate all the vacuum lines but everywhere I sprayed carb cleaner there was no change in the engine idle.

I plan on checking the timing and doing an on car cleaning of the fuel injectors. The engine has 114k miles on it so I'm sure the injectors need cleaning. I did notice though when I took the air filter lid off, it wreaked of gas underneath. The air filter though smelled fine and looked clean. I inherited the car and since there's no one that can tell me what maintenance has been done I can only assume its been a while since the injectors have been cleaned. I do know my grandfather put a new engine on it 12k miles ago though. If the timing and cleaning doesn't work I guess I'll have no choice but to replace the throttle position sensor and mass airflow sensor. Not sure if its either of these sensors though but I'm starting to run out of options. I'm banging my head against the wall because this problem is fustrating as hell. It started doing this out of the blue about a month ago.

Is there anything I'm missing or anyone have any suggestions?
 

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check the vacuum ports on the throttle body,,for the map,,see if there pluged with carbon ..
make sure the tb and intake are tight,,
egr could be stuck,pull and plug the vac. line and give it a few tapps on top...

check the timing,,,un plug the knock sensor,,,see if it still does it...

check the tps with a scantool or a meter...
i dont think you have a maf sensor on that motor...

check all the connections/grounds...:texas:
 
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