Very erratic idle and loss of power.

I've got a service appointment tomorrow, but my paranoia gets the best of me. This afternoon I was sitting at a light and my idle jumped to 1,500. I immediately thought it was due to the AC kicking in, but it wasnt. The idle proceeded to fluctuate between 1500 and 3000 consistently. Back and forth every few seconds. I pulled away from the light, pulled into a parking lot and shut the vehicle off. No warning lights, let the car 'rest' for a bit and restarted. The idle went right back to 1500 and started jumping again. At this point im only a few miles from home so i continued. Above 3500rmp the car loses power. Any thoughts?

Is there a model year designation for your car?

02 c4. sorry

Interesting problem. 1500-3500 rpm flectuation is really too high to reflect a vacuum leak or DME adjustment due to mixture. So I would have to say it is probably a throttle body/drive by wire issue. I wouldn't think it is the mass air flow sensor because that will set up the CEL, so......

Thanks. I'll post the prognosis on wednesday when i find out. Its one of the weirdest things ive seen a car do. Systematically 1500rpm to 3000rpm and back. over and over.

Same thing happened to my 2002 C2 Cab a few months back, with an Evo Flow intake! Turned the car off and it appeared to reset itself.

I had the same Idle problem first had the oxygen sensors changed because that was what the code read out showed. Fixed for a about a month. Then I changed the idle control switch worked for 2 months. Then I changed the throtle control switch. Now its perfect past 4 months. This is a a 99C2 with 77k miles already had a new mass air flow meter. Good luck these codes are not always correct.

saga continues. I went to start the car this morning to drive to my service appointment. The vehicle didnt want to start at first and when it did finally start it would jump to 1500rpm and then immediately stall. I didnt want to push the issue since the vehicle was idling all over the place and the PSM and ABS Failure light where also intermitantly flashing. very weird. needless to say, i missed my appointment and can't get the vehicle in the shop until next week! bummed.

Sounds like a ecu problem or vacum leak. Go check under the hood to see if there is any hose disconected or wire that you can reattach. If not you might want to try to reset the computer by disconnecting the battery for 5 minutes. Its not a fix, but it may get you to the shop.

Sometimes when a battery is low on juice, it can cause the car to get jumpy and go into limp modes. I don't know if that's the case here but it's worth a thought.

Update. Took the vehicle to a different dealer since they had open appointments. They said there where 7 different fault codes that where retreived and they want to replace the entire "throttle body". unfortunately they werent able to tell me whether or not this is waranteeable under a certified vehicle. In addition, ive had continuing problems with the vehicle not staying in alignment and the front end pulsing at high speed. This dealer is much more reputable but they are suggesting that i need to rebalance all four wheels and perform another 4 wheel alignment. Thats 2 aligments for me in the last month! I have hardly driven the car! Isnt there some sort of action I can take against dealer #1 for not being able to correct this problem? In the last two months ive Iin order) 1. Balanced all four wheels. (problem still exists) 2. 4wheel alignment (problem still exists, no change) 3. Balanced all four wheels (problem still exists) 4. Repaced 2 front tires with MINIMAL wear! (problem still exists, actually worse!) 5. 4wheel alignment (problem slightly better, car pulls to the right!) Talk about getting the shaft on this one? Has anyone had any luck correcting the problem at a new dealership and requesting that the existing dealership cover it? Total incompetence!

MAF

I just wanted to update this post for future reference if anyone faces similar problems. I got my vehicle back today and the following fault codes were retrieved from the computer. I don't know what they all mean, but heres the list: P1120, P1141, P1151, P1514, P0103, P1121, P1109 The remedy was replacement of the throttle body which was covered under certified warranty. The vehicle was serviced by Paul Miller Porsche in Jersey and the staff was extremely professional and knowledgeable. They also revealed that ALL 4 wheels were out of balance which completely amazes me since they were balanced by another dealership no more than 2 weeks ago! Lastly, Paul Miller Porsche even fixed some annoying interior noises (free of charge) that I brought to their attention.

Update to the Update. PSM and ABS lights are back on, with the same extremely bizarre idling problem. Vehicle goes back to the shop on Monday but this sure does screw up the weekend plans! Soooo pissed.

Clean the MAF.

I did. The dealer checked MAF and said it was not the root of the problem. In addition, the CEL light came on today when I went to move the vehicle out of the garage. Im really beginning to question the quality of these cars. With only 20k miles on ANY car, i should not be experiencing this many problems. ie. RMS, Throttle Body, etc etc. not a happy customer.

Update #3! Vehicle brought to dealer yesterday. Dealer states current fault codes lead them to believe that the MAF is bad. "MAF I ask?....At my last visit, didnt you tell me that there was no way possible that the MAF was the cause"? The service rep had no explanation. I cheerfully pick-up the vehicle today as I am about to embark on a mini-vacation our to Cape Cod...... No more than 50 yards out of the parking lot, the vehicle has NO acceleration past 2,000rpm!!!! Does the work **** mean anything? At this time, im super pissed, navigate through some illegal turns and get the vehicle back to the dealer. Serenity now...Serenity Now.... I check-in with the service rep and calmly say "did your service tech even road test the vehicle"?>? He said "he should have". I demand that the vehicle be looked at immediately and i wait for 2 hours in the showroom..........Later that afternoon, the service tech states that he does not know what the problem is but he "THINKS"....(keyword THINKS) that its the "gas pedal potentiometer?" which is NOT covered under CPO.......SOOO? what should i do? From what I understand this is a $500 part and there is no guarantee that its a fix.... I demanded that they get a regional tech into their shop to better diagnose. This new problem cannot be related to my existing problem and theres no way in hell im paying for it. Does'nt anyone know how to work on these cars? Second dealership, third visit....still no results.... To date, this vehicle has ruined no less than 3 summer vacations!

Go to a good independent mechanic... The dealers are incompetent... PM me if you are looking for recommendations... Ross

Update #4! Its a beautiful day. The sun is shining, no work for weeks and I get good news from my trusty friends at Porsche that my vehicle is ready! "Ready" I ask? This is great news! Its been nearly 2 weeks since my last true bonding experience with my beloved C4cab. New wing was installed since my last endevour, new Alpine head unit w/ sirius/Ipod, new Mbquartz, new MAF, new throttle body, interior rattle fixed.OOOOOF. This is going to be a great weekend! I gleefully pick das boot up at 2pm, greeted with smiles and I just needed to make a quick pit stop to see if my "front lip" spoiler had come in. I proceed to speak to Mr. (im really busy) Parts Guy to get a status and he responds "You don't need that front lip spoiler, they fall off all the time and people never replace them". "I dont need one" I reply? "nope, waste of money" Mr. Parts Guy replies. "are you sure?. Im fairly certain that all 02+ 996's outfitted with the carrera wing need to have the front lip installed to balance aerodynamics", i stated. "where did you get this info", Mr Parts Guy inquires..... "from researching on www.rennlist.com" i respond. "Rennlist?" he chuckles. "Lots of wild imaginations on that site"..... my response..."hmmmmm...... just order the ****ing thing. If you ordered it on Monday like i asked it would be here by now". Anyway....Back to the repair. The dealership replaced the DME and states this should be the ultimate fix. I'm on my way, immediately i hit the throttle (after warmup of course) and notice a much sparkier acceleration! Feels like a new car! I jump on to 287north headed home to the highlands of New Jersey and I'm delighted to finally have the vehicle back!. Some vintage metallica has somehow convinced me to really put the vehicle to the test and im quickly pacing @105 on 287. Police? No policia in site and quite honestly, not worried about them either! I exit 287, make the super fun jughandle exit onto 23 north.....rail the turn, throttle it up, get a little slippidy slide and im back on the the throttle! back on the throttle....back on the throttle? gues what? there is none.....No power above 1500RPM.!$$#$## The engine revs, but hardly any acceleration. Now this is real fun. I bee-line back to the dealership and low and behold im back in the wonderful 2001 A4 loaner car until at least next tuesday. Im beyond pissed. This car has been a handful, but has certainly done wonders for my interest in being intoxicated. I'll post an update next week. The joys of owning a porsche.

Diablo - man that sucks! Did you talk to the General Manager at the dealership about this yet? If not, it might be a good time to do so. I hope they get it figured out.

Bummer. I know.... I contemplated speaking to someone of higher authority but I wasn't sure what could be done. I'm usually the first person to "speak-up" but I really believe that their techs and their service advisor are doing the best they can. I can see the humility and frustration on their faces so at least I KNOW they are trying. Other than taking the vehicle to a THIRD dealership, or taking the vehicle private, theres not much else i can do right? Vehicle is still covered under CPO so I dont really feel like paying out-of-pocket. I jokingly tried to convince the service advisor to sell me an 07 turbo at cost, but that didnt really work This is really unfortunate. I was hoping to take the vehicle to Whistler BC next week and even if the car is finished in time, i have no faith in it.

Speaking to a higher authority may get everything covered financially, I mean having to go back and forth to the dealership is precious time off your life Porsche should be told this. Also, what's a DME? My next guess is it's still the MAF or the ECU other than that there really is nothing left but spark plugs.

that really sucks ask the dealer to give u a better loaner. at least a boxster. so u have some fun for the weekend!

Diablo, I am getting similar behaviour, cannot go above 4000 RPM, and Durametric shows faults P1120 and P1121. How and what else did you do to fix the problem?

How and what else did you do to fix the problem? Doesn't appear to be fixed!

Cats.....

Cats? aren't there sensors after the cats that would trigger an error code?

Had a similar experience some year ago on a Saab 93 Viggen. cats were completely fouled up causing lack of acceleration and rough idle. Also took about 4 dealer visits to sort out (after everything engine related had been replaced under waranty).