Mystery Problem, Limited RPMs

[Paul]

[virgosunleomoon]

ok, I didn't start messing with the AOS until after the problems started. If I was the pedal sensor, that wouldnt explain the rough start. It only had one fault code and its the one I posted earlier.

I am just waiting on one more speciality tool to arrive and I am going to...
1. Replace the fuel pump and sending unit (snapped the top off the old sending unit)
2. Re-install battery and attempt start. If it fails.
3. Take fuel pressure at fuel rail. (I have the tool now.)
4. Replace fuel filter and try again. (I have a new one.)
5. Peplace fuel pump relay and try again. (I have a new one)
6. Check pedal sensor and try again.
7. Return to drawing board.

Don't give up on me guys, I enjoy the feedback and ideas.

[particlewave]

Keep in mind that there are 2 potentiometers for the e-gas for redundancy. When 1 fails, RPMs are limited by the ECU exactly as you describe.
Sorry if it's been said before.

[virgosunleomoon]

Originally Posted by particlewave

Keep in mind that there are 2 potentiometers for the e-gas for redundancy. When 1 fails, RPMs are limited by the ECU exactly as you describe.
Sorry if it's been said before.

ok, where are those 2 "potentiometers"?

I replaced the fuel pump and sending unit.
I replaced the fuel filter.
I have a new fuel pump relay that didn't make a change.

My throttle body is apart in my hands right now, will put it back together clean and see what happens. not too much oil in there, seems to be ok. i will post later.

PS - the fancy fuel pressure hose I bought from the dealership, it has a metric end and I cant screw it onto the gauge I have. -grrr-

[virgosunleomoon]

and Paul, good point on the connection for the throttle body, I will make sure its tight when it goes back in.

PS - AND WE STILL HAVE P1502 for a CEL.... (Throttle Body not put back together yet...)

[virgosunleomoon]

PROBLEM SOLVED - In the end, it was the P1502 code that was the problem and the cure. My new Can-Tech OBD II tool showed the P1502 code and below it it said "Fuel Pump Relay End Limit. Porsche Part $11" Seeing this I assumed it was a Fuel Pump Relay code. After changing the fuel pump/sending unit/fuel filter and trying out my new fuel pump relay, I was discouraged so I texted my buddy who is the head mechanic at the Porsche dealership (yeah, tried to do it without him) and he said 1502 was a throttle body error code. Not happy hearing this, I opened my Bentley Service Manual and looked it up.

P1502 - Throttle Jacking Unit Spring Test

I almost crapped my pants. Why the hell did the OBD reader say "Fuel Pump Relay?" I couldn't believe it. I took the TB apart, cleaned it real good, exercised it, put it all back together, and started it up. Very rough idle but I could get it to 2300rpms!! On the right track I said! So I did the EGAS remapping thing where you turn the key to on for a minute and then off for ten seconds and start it. same thing. Then I cleared the code with the OBD reader and started it up.

OMG, it was like a new car. Not only did I have my revs back but after the car got to temperature, there was no flutter in the idle. I was so happy, I took it out and set a personal record for fastest speed on four wheels. 145mph

The throttle body wasn't really THAT dirty so I think I am just going to order a new one and throw it in there so I don't have any issues in the future.

I want to thank everyone who contributed to the effort in getting my baby back to normal. Got 3 days at Watkins Glen August 22nd, 23rd, and 24th. I was starting to sweat a little. -wink-