sm

Brett,

Any updates? Since it's free, I would do the tests that Flash968 and others are suggesting.

I finally drove my car after added more oil to my A/C system and it's noticeably smoother with the A/C on than before, but YMMV.

Good luck!

Brett951

No real update yet, I'm in AZ at the moment (saw a black 968 tip coupe outside of "The Native New Yorker" last night, anybody on here's?) for a class.
These are done, no problem found:
- check your battery and main ground connections - tighten them and not just a visual check
- make sure the battery is topped up with distilled water - do not use tap water
- check your belt tension - a loose belt can do that

I didn't have time to check the alternator before I left, taking the belt off. However, if it is the voltage regulator portion of the alternator, which would be more likely given the symptoms, spinning it won't allow me to rule it out since that really just gives you an idea of the bushings and bearings (correct me if I'm wrong on this thinking though!)

We don't have a Pep Boys around here, and I wouldn't trust any of the parts stores with charing systems tests - I've only seen them use those tests to sell alternators and/or batteries - usually picking the wrong one to fix a problem.

So, this is really weird. On the one hand I suspect the compressor (and not just because the service manager at the dealer did), because a) going through the PO's records, the AC was recharged after the car sat for a while. So if stuff leaked and then it sat and then it was simply refilled, it could have ruined stuff (seals, etc.) inside, b) I can't make it stumble under any load other then the AC.
But I'm not conviced of that either, because I would think if it was that bad, it would seize (though maybe sm, your symptoms were similar?) AND I don't think a drop in RPMs should affect the voltage that much like I'm seeing.
So - maybe I am chasing multiple problems - ground wire and/or alternator + AC compressor???
The car has an appointment with the dealer's service dept on Friday (tomorrow). I think I'll have THEM check the charging system (giving them the results I had) as well as a full check on the AC system.
I hate to pay others to fix my car, but chasing multiple possible contirbuting factors like this requires more diagnostic equip/know-how then I have.

Slighty off-subject - anyone from the Portland area reading this board? I had thought that International Motorsports was well respected in Porsche circles here. However, going through PO records, the steering rack was replaced by the second owner, and then replaced again by the third owner about 250 miles, and about 1 year, later (or at least they were each billed for it) - at the same shop!!! What the heck?!? Makes me not want to take my car there (though I haven't talked to them and asked for an explanation yet either )

Anyways, thanks for the advice, for pointing me to at least some testing myself first. And I will Definitely post the final outcome here

flash968

you are correct about the spin test only showing the conditions of the bearings and such

the voltage regulator is inexpensive and easy to change - 15 bucks for an aftermarket one that works fine, or 40 for the bosch - takes 5 minutes - no need to remove the alternator - i was going to point you there after you had done the spin test

good thought on the dealer doing the charging system check - make sure you get an amp output reading both at idle and at higher rev and with a load on - voltage output is not enough - you could have an alternator that puts out 14.5 volts, but only 5 amps - also make sure they do a hydrometer check on your battery

by the way, for future reference, if you don't have a pep boys, grand auto and other stores like that can do the same thing

weird about the steering rack - i think i'd stay away from there too

Brett951

Dealer service reports that AC compressor and charging system and battery all check out. Fault code is that the Hall sender is bad...

flash968

ok - this is one of those oddball porsche things that really seem overcomplicated to me - somebody fill me in on the hall sender - i've heard about it - what hall? what's it sending and to where? i take it it's not the kid who assigns the hall monitors in elementary school

RajDatta

Another name for reference sensor. Tells the DME TDC.
Raj

flash968

i wonder why it only seemed to cause it to stumble with the ac on? that doesn't seem to make sense

Brett951

Doing a search on here for hall sender or hall sensor and you have other people with intermittent, but reproducible problems like mine. Seems like one of its functions is to retard timing - maybe I'm having the timing retarded somewhat and with the extra load of the AC it just gets REALLY noticeable... Here's hoping the thing runs even better when I get it back (decided to let them do it since they were going to charge almost 1/2 the total build for "diagnotic time" anyways, and this way we can actally get away on vaction instead of me working on the car...)...

-Brett

hosrom_951

So your problem turned out to be the TDC sensor? did they replace it and is it running fine now?

Zneed4speed

I hope that your problem is solved but I'll bet it isn't. Did they check the AC "pressure switch"? If the prob is still there ask them to check the AC psi and the pressure switch.

Brett951

The dealer did replace the hall sensor, and yes, the problem has gone away, I've driven the car with the AC on for a couple of days to see if it comes back, but it seems all better. The car also seems quicker then before, and I *think* may be getting better gas milage, but its too soon to tell for sure on the mileage. I also haven't done any acceleration times before/after, but my kids think it is faster then before. The car, with the AC off was pretty quick, thought not as quick as my Turbo before. Now its closer...
I'll keep an eye on the AC pressure switch and psi if the problem comes back...

-Brett

terryjenner

Does anyone have a Porsche part number and digital picture of the idle control valve on the 968? I hear it's under the intake, do you mean the intake manifold or the intake plenum where the MAF sensor is located?

Terry

RajDatta

Its right under the throttle body. Its approx 3-4 inches long with an inlet and an outlet port and a electrical connector on top. If you were to look at the throttle body from top, you will see the idle stabilizer valve right underneath it.
Raj

terryjenner

Got it. Is there a special tool for those hose clamps? Can they be reused, or should I go down and get some before I begin? Also, I'm reading that you should clean it out with carb/choke cleaner. Anything else I need to know?

Before I dive in, let me explain what my car does. At idle with A/C off, car idles at about 900-925 rpm. Turn A/C on and idle drops intermittently to about 800, then makes a slight recovery, but this causes some shaking throughout the engine. Car blows cold and has no apparent oil leak from A/C compressor, belts recently tightened, new Optima gel cell battery installed last week (problem existed before battery replacement), battery terminal connections are tight, new DME relay installed,( ground will be checked today). I would like to oil the compressor as well, so if anyone can write me a line, I'd appreciate it.

thanks

Terry