2001 Cobra (kind of) Revs high between shifts

Hi all,

I am hoping you can help me out as I have been searching on this topic for a while and not yet found any definitive notion as to what my car's issue might be. I have a 2002 Panoz Esperante, which powered by a 2001 Cobra engine and most of the same drivetrain. My headaches with the car started a few weeks ago when I ran it up near the red line under WOT and suddenly I had a CEL (P0190). The car itself drives pretty well, though there are a couple of unsettling issues: hesitation / bucking around 1800 RPM (but its done this for a while) and the revs are much slower to drop between shifts than they used to be (hanging for 4-5 seconds, this is brand new since the CEL). Based on the searches made so far, I have already replaced the FRPS and the IAC. Certainly there are some unknowns, chief among them the supercharger kit and what I suspect to be a bad tune, but the high revs is just really bugging me. Just thought I would ask before I take it to the shop and make sure there isn't some cheap stone left unturned. Any ideas/help is appreciated.

Thanks!

Mattstang04 said:

I see you're supercharged. Is that something that you've put on recently? What kind of supercharger and do you have a cold air kit on the supercharger inlet? Pretty much list your mods.

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Unfortunately, I do not have a great deal of information regarding the mods on the car. The supercharger was put on quite some time ago (5+ years), that much I do know. It does have a cold air intake and intercooler as well.

Mattstang04 said:

It could be a tune issue but there's a good chance that there's a vacuum leak. If its an air to air intercooler there's plenty of connections between piping that could need some tightening up. If you replaced the iac i recommend disconnecting the battery until the computer goes into relearn mode. Then it will drive like crap for a while before gradually getting better. Shoot some throttle body cleaner around there intake and supercharger, if the engine dies down you know you're close to a vacuum leak.

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Thanks, I'll give that a shot. I definitely think there is an issue with the tune, but that seems harder to deal with. Any notion as to how long the battery should be disconnected to trigger the relearning mode?

wmburns said:

My vote is that the fuel rail pressure sensor (FRPS) diaphragm is ruptured. This goes double since the problem began after a WOT run.

Or there's an electrical problem to/from the FRPS.

Anytime the PCM calls out a circuit malfunction it means there's something so wrong with the circuit that the PCM is not able to perform any diagnosis.

Check the FRPS intake vacuum reference line for the raw gas. Double check the FRPS electrical connector to be sure contacts are clean and tight.

Regarding the re-learning. It's only necessary to disconnect the battery for a minute or so. Clearing DTC codes will also force a re-learn.

>>From Ford service manual
P0190 - Fuel Rail Pressure Sensor Circuit Malfunction (FRP)

• VREF open in harness.
• VREF open in sensor.
• VREF open in PCM.

Verify VREF voltage between 4.0 and 6.0V.

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Sorry, just getting into this topic. If I replaced the FPRS already should that have solved the issue if it is the diaphragm or is that something outside of the sensor itself? FWIW, the P0190 code and CEL is back again even after replacing the sensor.