NCdog

Hi All!

I'm having a pretty bad experience with my new manual 04TT (36kmi).

I've scoured all the posts I can find but can't find anything that offers much help with my problem - hopefully one of you can point me in the right direction!

I had the clutch replaced by my local tech when I bought the car, I mention this because I have read that it could cause an ABS/PSM error.

Shortly thereafter one day while sitting (engine running) it threw an ABS/PSM/CEL warning.

About the same time I suddenly noticed that the 800rpm idle would get lumpy after a few minutes following driving the car.

Took it back to my tech(I'm 3hrs from the dealer) for repair.

His computer indicated a bad MAS, as did his voltmeter, so we replaced the MAS - to no avail, same problem.

However the ABS/PSM lights didn't come on until I had driven the care a ways and then sat at idle. Restarting the car later it would show no warning lights - until the end of a drive when idling for a few minutes.

Got another computer which showed MAS, throttle body, and butterfly as potential problems.

Removed and cleaned the throttle body - had some black grime, no oil- and also opened the electronics portion, which looked perfectly clean.

Started car, warmed her up, drove to end of driveway - ABS/PSM lights again.
Drove 4 miles and sat at idle - which was now 1200.

Came back to start 30 minutes later - normal 800 rpm for a few minutes, then the idle slowly climbed to 1100 steady for a minute or so, then ABS/PSM came on again, accompanied by a quick drop to a lumpy 800 rpm.

Also at cold startup it runs a little rough for a minute then smooths out to an even 800 since we did the above.

I should mention that my tech smoked the car for leaks - nothing.

Anybody have any ideas before I take car to the dealer?

Thanks!!

fpb111

Stock intake system?

Carlo_Carrera

And does it have a tune?

"02996ttx50

sounds like a faulty throttle body. what codes came up? eg "0507" "idle high"? and since you've tested for leaks it lends even more credence to a faulty tb as the cause since its presumably "electronic" and not a vac leak etc.

try driving awhile with the maf unplugged. if it stops idle hunting? the maf may still be bad. was it a "new" bosch you tried?

garrett376

A failed/sticking "check valve #16" in my 03 caused just as you described above: intermittent very rough idle when warm with ABS/PSM errors and no signs of intake leaking to the outside when pressure tested. The valve is cheap... getting to it is the adventure!

996tt6156R

If your getting the throttle jacking codes then clean your throttle body and flapper. If it's not that then you have a boost leak.

What are the codes?

NCdog

Answers to questions:

Stock intake system

Remus exhaust

No tune

Throttle body removed and cleaned (wasn't very dirty)

To my knowledge no throttle jacking codes - I will post codes (have to get them from tech)

Also when I remove the oil fill cap there is no detectible vacuum and covering the opening doesn't
alter the idle at all - any help?

"02996ttx50

have you driven it yet with the MAF "unplugged" and was it NEW? or a re-mfg "knockoff" part# 124.00?

this can often help to rule in/out a MAF as a cause or contributing. still sounds like a tb issue though.

once you get the codes, that should help.

NCdog

The codes are P102, P1601, and P1101.

Only drove the car unplugged when testing the original MAF to confirm incorrect readings from the voltmeter.

Replaced with genuine Bosch MAF.

"02996ttx50

generic "obd" info but most all pointing to a maf issue still:

What causes the P1102 code?

Some possible causes of a P1102 trouble code includes shorted wiring or a loose connection within the MAF sensor harness, an air leak in the vacuum system before or after the sensor, or a bad or dirty MAF sensor. A clogged MAF sensor screen can also cause the voltage from the MAF sensor to register as too low. In some cases, the problem is caused by a poor electrical connection with the MAF sensor circuit.

What are the symptoms of the P1102 code?

Some of the more common symptoms of a P1102 trouble code storage include an erratically running engine, less power when accelerating, and stalling while idling. Another problem caused by a P1102 trouble code is problems with the fuel mixture, which can lead to problems with the vehicle's engine.

P1102 code definition

When the voltage coming from the Mass Air Flow (MAF) sensor to the Powertrain Control Module (PCM) is low but within range, a P1102 trouble code is stored. Other trouble codes related to this code include a P1100, P1101, P1103, and P1104 code.

1601 doesn't make sense to me but I'm outa my depth GL w it.

Macster

P0102: Mass air flow sensor -- below limit.

Possible fault cause: open circuit, short circuit to ground, mass air flow sensor faulty.

For the faulty mass air flow sensor with the engine running if the sensor puts out 0.9V to 1.1V replace the sensor. It should put out 1.2V to 1.5V.


p1101: Input variables, charge measurement -- below limit (or above limit).

Possible fault cause: heavily soiled throttle, throttle damaged, mass air flow sensor.


P1601: CAN timeout instrument cluster -- signal implausible.

Possible fault cause: instrument cluster faulty. Note: If one CAN bus fault is stored, the cruise control system is out of order.

CAN bus faults can be caused by a control module reset. The fault is then indicated as "Not present".


I'd go after errors P0102 and P1101 first. These point to the MAF but a wiring or circuit problem could exist. Any chance mice have been at the car?

Has anyone been at the wiring? Had the cluster been out for some reason?

NCdog

I have no way of knowing whether the cluster has been out or mice have been at the car. I purchased the car in early January from a retail outlet. The carfax is clean and the car was serviced regularly by a Porsche dealer through 30k and 2010. After that I have no records.

The car ran fine the first few weeks I had it. As I mentioned before this problem showed up right after I had the clutch replaced. Any possible connection?

Started it yesterday from cold, came to operating temperature. After a few minutes at 800rpm it slowly climbed to 1100 for about a minute, then it threw the abs/psm code followed by a drop to a lumpy 800rpm idle.

We are going to check electrical values for MAF and throttle body and resmoke - I'll keep you posted.

"02996ttx50

my uneducated "guess" is that the clutch work and the appearance of these symptoms is coincidental.

i had the exact same issues and once you are able to test the "values" for the TB, then you'll ( presumably? ) "know more". but for my money ( and time ) i'd put in a new TB since you already have a NEW OEM maf since even you've ruled out ( 100%? ) a vac leak ( incl the #16 check valve/all intake hoses etc..etc ) then since all your codes appear to point to maf/TB issues? i would imagine that replacing them both at the same time would cure this. idle "hunting" is often any/all MAF/TB ( electrical ) VAC leaks ( not electrical ) as you know. this'd be easier to guess at if you did in fact have a P0507 code.

be interesting to see what the values of the electrical output of your TB is though. that's again, out of my depth and since they can be had for $238.00 as i just bought one. i'll "throw a part" if they are under $500 GL.

NCdog

Got the car back from the shop about a week ago and it's running great at last.

The problems were a bad MAF and apparently a dirty TB, which I removed and cleaned myself.

When it still didn't run right took her back to the shop again. He resmoked and found a clamp yours truly didn't install after cleaning the TB. Now all is well.

Thanks to all who responded!

RngTrtl

While reading I was thinking vacuum leak. glad you got it sorted.