judd944

It is 50 degrees and raining here in lexington, I drove my Porsche for the first time since Sunday. It had a little hesitation starting but fired up. after I came to my first stop about a minute into my trip the engine began to idle low. I pulled out into traffic and when I tried to accelerate the RPM's just dropped low. I could only get the car to go by slowly reving the engine to about 5k then dropping the clutch. for the next 2 stoplights it stalled out every time I let the RPM's get low. Upon start up each time the starter moved slower. I parked it and got a ride to work. Does this just sound like a battery? when I would rev the engine it would backfire and stumble. I was planning on working on my BMW tonight, It looks like it will be a German Car weekend!

Jim 944S

Sounds like something else. The battery should not be an issue once the alternator starts turning (if the alternator is putting out properly). Constant starting may drain the battery faster than the alternator can put back the power, but again, I don't think the battery is your primary concern. My alternator puts out full power at idle, no problem.

Now that I've merely said what it is not... can someone with better adivce chime in? Perhaps vaccum line problems?

Jim 1987 944S (Oh, I wish I was in the land of Horsey-hockie, up in the blue grass of Ken-tocky, look away, look away, look away, Ken-tockys' GRAND!!!)

Mighty Shilling

Sounds like what happened when i tossed my alternator belt a couple weeks ago. so check the alternator. good luck!

Epic2112

I agree, might be the alternator, try hooking the car up with jumper cables and see what happens. It also might be that you got some junk stuf in your fuel lines maybe, but I don't know how likely that is. When was the last time you changed your fuel filter, and was the tank mostly empty when this happened?

judd944

Fuel filter could stand to be changed. I have a spare. my tank is just under half full. people here at work are saying it could be the alt. I may check that first. Jumping the car should work to get me home. I will let you guys know what I find out.

Macfreak007

If its the alternator the idle will get lower and lower, and it will stumble on rev, just like yours did. Eventually it will just die, like a dead battery. Don't jump start it, or at least disconnect the grounds when you do. The DME doesn't like it. Take it to Autozone if you can and see if the alt went out. Otherwise I would guess battery. Use a multimeter to check both if you can. Volts should be about 12 with car off, then when you start it, it should go up. that would mean the alt is charging.

hacker-pschorr

I don't see how a bad alternator would require him to rev it to 5k to keep it from dying. Running at 5k vs 2k will only drain the battery faster and put more of a load on the alternator.

judd944

Should I try to drive it back to the apartment (less than 1 mile) or should I get it flatbedded? Driving to autozone is out of the question. (too far) should I just remove the alt. and take it in to them to test? Anybody have a spare Alt laying around? I sold all my spare ones from parts cars when I moved to KY. Doh!

CO944

I would highly recommend the alt. I have had this exact issue with
several cars. flatbed it back to your house.. remove the alt and have
it tested. Check the batt. while you are at it.. When alternators go bad
generally they take a batt. with them.

Macfreak007

less than a mile should be covered by insurance if you have state farm towing insurance, or AAA. Thats a no brainer, if not, charge the batt up and drive it, should be able to make it a mile.

RMills944

I"d take a can of starting fluid with you and look for vaccuum leaks. It sounds like there is a vaccuum leak between the AFM and the throttlebody. Check that - it may be just a hose clamp. The same thing happened to me and it cost me $.35 for a new hose clamp and it's been great since.

83na944

You can check the output of the alternator by putting a voltmeter across the battery terminals. You should get something over 13 volts. If you're getting low voltage, you might be able to just replace the voltage regulator. Its an easy repair.

BTW, any chance the fuel pump was running all of the time? Any smoke of smell of raw gas? Those would be symptoms of a failed FPR.

judd944

Well I got the car home a few hours ago. Very strange, I pulled into a hardware store and told them my car was having trouble and not to tow the car. The owner heard this and put his buisness card in my window, he is rebuilding a 944 S2. Broken timing belt. He also has a 97 540i that is black. crazy we both have the same kinds of cars. He is in the PCA and the BMWCCA too! Anyways he popped my hood and he showed me the ground where it had some corrosion on it, shook it and told me to try to crank it. The car started up fine and I drove home. the only thing that was weird was when I let off the gas and let the car go back to idle it drops a little low, shudders then goes back to ~1050 rpm. I am going to clean my Grounds this weekend! On a side note I got my 540 problem fixed tonight. Wahoo German cars are back on the road!

Yabo

where was this ground? just for the rest of us to have that trick in our book. Was it the one near the refference sensors?

Jim 944S

Excellent, Judd!!! I'm glad you discovered the nature the aggrevation!!!

Enjoy that beautiful state you're in! I'm envious!

Jim 1987 944S