Jon Hendrix
Junior Member
Hey yall, putting this up here to get some extra thoughts.
My car runs insanely rough on startup, dumping fuel and shooting stft up to about +80%
After about 30-40seconds of this idle will pick up and it will become driveable but still run rich.
When i first had this issue I had codes for the 02 sensor circuits, after testing it i replaced both upstream 02 sensors, issue did not resolve. A while later I pulled P1237, lost communication with the FPDM. I jumped the FPDM out of the circuit and it started up just fine. After this I replaced the FPDM with an OEM, and the issue still did not resolve. At this point i became suspicious of a fueling issue, and began to monitor the FRP, which fluctuates from 34-44 psi on these rough idles. That remains out of spec, but not out of spec enough to cause this issue imo.
The car was cammed and tuned by the previous owner, and im getting worried it will come down to an issue with the valvetrain, but still have many more tests i can do.
My first order of buisness is confirming once again that the bank 2 02 sensor circuit is functional, then to swap it with another known operational 02 sensor. Then i will smoke test the exhaust to see if theres a manifold leak. I have run quite a few similar tests and am running out of ideas, any thoughts or suggestions would be very much appreciated
Also it is high mileage and i believe it still has original injectors and maybe plugs as well, as a rule i dont like to throw parts at issues, but i may go ahead and change these from a maintenance perspective hoping it will also resolve the issue.
My car runs insanely rough on startup, dumping fuel and shooting stft up to about +80%
After about 30-40seconds of this idle will pick up and it will become driveable but still run rich.
When i first had this issue I had codes for the 02 sensor circuits, after testing it i replaced both upstream 02 sensors, issue did not resolve. A while later I pulled P1237, lost communication with the FPDM. I jumped the FPDM out of the circuit and it started up just fine. After this I replaced the FPDM with an OEM, and the issue still did not resolve. At this point i became suspicious of a fueling issue, and began to monitor the FRP, which fluctuates from 34-44 psi on these rough idles. That remains out of spec, but not out of spec enough to cause this issue imo.
The car was cammed and tuned by the previous owner, and im getting worried it will come down to an issue with the valvetrain, but still have many more tests i can do.
My first order of buisness is confirming once again that the bank 2 02 sensor circuit is functional, then to swap it with another known operational 02 sensor. Then i will smoke test the exhaust to see if theres a manifold leak. I have run quite a few similar tests and am running out of ideas, any thoughts or suggestions would be very much appreciated
Also it is high mileage and i believe it still has original injectors and maybe plugs as well, as a rule i dont like to throw parts at issues, but i may go ahead and change these from a maintenance perspective hoping it will also resolve the issue.
