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Discussion Starter #1 (Edited)
Car started acting up following a car wash today. 1995 LT1

No codes.

As stated it feels like it stumbles at low RPM high TPS. I data logged it and drove around with the Fuel Pressure Tester strapped to the windshield.

Results of Test Drive:
Fuel Pressure was 42 at key on. 32 at Idle and seemed to run all the way back up to 40-42 with rpm. When the stutter occurs, the L-term fuel trims spike to 136-142. mV on the O2's seem to cycle properly. I have at most 0.1 to 0.2 degrees of spark retard being called for.

Things I've checked:
Intake/Exhaust/Vacuum Lines: All vacuum lines are intact and connected. Can't find any intake leaks. Do possibly have an exhaust leak. But can't feel/find it. The only thing that seems out of place is the EGR valve is sticky, however it's disabled in the PCM so I can't see this suddenly being the issue.

Ignition: No arcing under the hood and the plugs have maybe 15k on them since I changed them with the motor swap. MSD Cap and Rotor has maybe 15-20k on it as well. Opti Vent harness appears to work properly as well.

Fuel: As stated in the test drive results; 42 psi key on, drops and holds at 40 psi once the pump stops running. 32 psi at idle. Anywhere from 32 to 44 psi as the driving conditions change.



What should I be looking for? Intake leak that only manifests itself at high load, low rpm?

Help! I'm supposed to drive from Wichita to Minneapolis for Christmas. Also sorry for the long post.

- Brian
 

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Double-check the coil wire for arcing, esp. around the boots. Also, when was the last time you cleaned the little resistor wires inside the MAF? I got water sucked into my air filter real good once in an automated high-pressure car wash, and my car ran nasty until I cleaned my MAF out with qd elec. cleaner and q-tips. Worst case is the opti somehow got a little moisture inside it, but it still could dry out with time since you verified the OVH is functioning properly.
 

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Discussion Starter #3
I can no longer get the car to recreate the stutter. Therefore I am leaning toward the conclusion that something did not like getting wet. I have no idea what. I have not re-datalogged yet so I don't know if the lean condition still exists.
 

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At low RPM/high trottle the pressure in the cylinders is very high and that is hard on the ignition system. If an ignition component is starting to show it's age you'll see it missfire at high cylinder pressure conditions or high RPM.
 
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