My 01 996tt starts, surges with poor idle quality and the throttle is not responding to pedal input. I give it gas and engine acts like no additional fuel going in. Idle eventually smoothes out but no rpm chang and will not "rev up". Has happened before. I shut off cleaned MAF and worked OK before. Is this fuel pump, air pump, MAF or what? Scared to drive and get stranded. No dealer close by so this is an hour plus tow! Suggestions?

 

Any codes?

 

No codes. Has thrown codes before with similar reactions and cleaning maf and restarting seemed to cure those. Occaisionally I would go over a stiff bump and code would throw with sporadic idleing but would boost and drive fine. I just retried to drive after cleaning maf and car would start with irregular idle but this time it would let me give it gas. I drove a couple of miles and boost is being limited to .2 or .3. Seems like I am in limp mode. Never been in this mode before even if idle was rough. I am contemplating having it towed to dealer as I don't want to have to leave it on the side of the road if it cuts off and wont restart. It would drive ok but no real boost and would not downshift even if put to the floor.

 

It could be the fuel pump. If original, there is a small U-shape rubber hose that can split and cause issues. If it is the pump you can either get the revised pump assembly or find a fuel safe replacement u-bend line. I've read on reenlist that the gt3 guys buy this kit for the hose.

http://www.scantechproducts.com/carp...-50.5142.1.php

 

I'm betting its the maf. Cleaning only does so much. This is how my car acted with a blown maf and no amount of cleaning would bring it back to life. If it were just a boost leak, and nothing else, I think the car would pretty much drive normal except the boost would build slower and would be capped at .4 (I believe that is the limp mode limit for when you have a boost leak...it was when I split my f-hose). Good luck.

 

Since you mentioned cleaning the MAF has helped fix the problem in the past it sounds like your MAF could be shot. If the MAF is bad no amount of cleaning will fix it. Without the car throwing any codes though, this is like shooting in the dark though.

Looks like I just posted at the same time as Scott with the same answer. Good thinking

 

Huge vacuum leak?

 

I second the MAF being bad. Sounds exactly like what happens when it goes... You said you dont drive it so its probably a matter of a mile or 2 before both PSM and ABS lights come on.

 

un-plug the MAF, drive it unplugged without going into boost and see if it resolves your issue. If all the issues go away, go get yourself a new MAF and that should fix your problem

 

Guys,
Thanks for all the replies. Here is an update. I cleaned the MAF unhooked battery and waited 30 min to reset DME and when I went to start it, it was still surging and took a while to idle right. I was able to drive the car so I headed to the appointment to have the car worked on. I got about 5 miles from the house when the throttle stopped responding. Again I would give it gas but nothing would happen. It was like the drive by wire was totally unhooked. I shut it off and restarted a couple times and eventually idle smoothed back out some so I hit the interstate and headed to the mechanic (1 hour away!) I know it was risky but it wasn't going to fix itself in my garage and I had already taken the day off so off I went. I got all the way to Columbia SC with no more issues except car would not boost over .2 or .3 but still got 25 miles to the gallon the whole way going75-85 most of the time. When the mechanic read the codes there were about8 codes that all related to the throttle in some way shape or form. I did not write down the codes but he tried to clear them and some did and some did not. He did some research and decided to to a throttle calibration sequence. After doing this it allowed him to clear all the codes. We test drove the car and it was all fine, boosted well, downshifting started working again and idle was smooth. I shut off and recrancked car about 3 time before I left his shop. I drove about an hour with no cel and no problems but on the way home I dipped back into throttle to pas someone and noticed thesyptoms were back. No downshift and little to no boost. No cel but car is back in limp mode. I drove all the way home like this with a smooth idle but the other symptoms are still there. Has anyone ever had a problem with the throttle body or position sensor or anything related to the throttle? By the way when the codes were first read, none of them were related to the MAF. I had gotten abs psm light once or twice in the past but the car never exhibited the other symptoms. I realize the MAF could be suspect but it just does not seem like this is the only cause. By the way my original appointment was to install the 997tt trans mount and yes my old mount was torn when we got it out and looked at it. Not as bad as some I have seen but torn through on both sides.

 

Thankfully I've never had any problem with my Porsches E-Gas systems. A few owners have reported problems, but problems in this area are rare.

But not unknown as I think you know by now.

The error codes probably pointed to the cause of the problem and it probably involves replacing some or part of the E-Gas system.

You have two problems. The car is sick is problem #1 and problem #2 is you need to find a shop that won't just erase codes and do some goofy recalibation step but instead knows what the codes mean, knows the proper diagnostic steps to follow, follows them, and fixes the problem right, the first time.

Sincerely,

Macster.

 

fI talked to the mechanic and he still had the piece of paper he wrote down the codes on. They are p0121,p1121, p1122,p1503,p1505, p1510,p1511, p1514. These all seem to mostly be something throtle realated. Not sure if it would be the Throttle position sensor at the y pipe or the one down near the gas pedal, One of these could be maf but the rest seem to be throttle related. Any clues. As I said there were times that the throttle did not produce any change in engine rpm.j I think it is a throttle position sensor or something in the drive by wire.

 

P0121 is throttle value signal implausible. Possible fault causes: open or short circuit in wiring. Throttle position sensor faulty. DME control module faulty.

P1121 is throttle position sensor 1 signal implausible, or below limit, or above limit. Possible fault causes: open circuit in wiring, short circuit in wiring, throttle position sensor faulty, DME control module faulty.

P1503 is throttle jacking unit, position error, signal implausible. Possible fault causes: short circuit in wiring harness. Sluggish throttle.

P1510 is throttle jacking unit exchange detection without adaptation, signal implausible.

P1511 is throttle jacking unit abortion of test due to negative influence of ambient condition. Possible cause: Starting vehicle during adaptation of throttle part.

P1514 is throttle jacking unit lower mechanical stop - signal implausible. Possible fault cause: No adaptation values available despite repeated adaptations.

For each of the above there are tests available that require making voltage tests or reading out fault memory after a performing an adaptation (switching on ignition for 60 seconds without touching the accelerator pedal) then turning off the ignition for at least 10 seconds, and a few other tests.

Too much to type in.

I'm going to be away from my office/computer and my references until Tuesday. If you can wait that long I can make a copy of the tests and send this via email to you. (The copy will be electronic, in PDF form.)

Send me an email and I'll respond when I return to the office on Tuesday.

Sincerely,

Macster.

 

Thanks for the reply. My email is good772@comcast.net Let me know what you find when you can. Thanks again.
John

 

Sorry for pushing such a old thread up, but I am having the same issue and throwing a lot of codes exactly like yours. p0121,p1121, p1122,p1503,p1505, p1510,p1511, p1514, it had to be on tow and is not drive-able . Can you please advise whats the fix finally? Thanks.