won't start unless pedaled
Thread Starter
Race Car
Joined: Nov 2004
Posts: 4,951
Likes: 1
From: Wisconsin
won't start unless pedaled
when starting my car cold, I have to hold the gas down and start the car and hold the idle for the car. It won't idle itself until the car has warmed a while. In these temps, I'd be frozen before the car warms up. I searched, and found reference to head temp sensor or O2 sensor. Now remember, I've had idle issues since I got the car- higher idle ~950 to 1000 rpm, and it also dies when I had the AC on coming to a stop.
Any suggestions?
Any suggestions?
Burning Brakes
Joined: Jul 2005
Posts: 872
Likes: 1
From: Naples, FL.
Jim, shout it out man, I got up this morning and 46 degrees in Naples, is too damn cold, what is it in Altamonte 38.... I went to college at Stetson and actually spent alot of time in Altamonte, neat place, back in the day when Porsche of Orlando, was Contemporary Cars.. good times.
Burning Brakes
Joined: Oct 2005
Posts: 828
Likes: 0
I may be wrong and I am certainly not a 964 expert, but I recall from other car experience that flooring the gas pedal when starting a fuel injected engine does not help. Only good for carburators. Being in Wisconsin in winter, maybe you have ice in the fuel line or the fuel filter is dirty. I had this problem with a BMW with erratic idle RPM's and I'm pretty sure it was a leaky vacuum line but not positive. I do remember the fix was simple and cheap.
Pro
Joined: Jan 2005
Posts: 701
Likes: 6
From: St. Albert, Alberta, Canada
I've got the exact same problem - won't idle on first start up when cold unless I blip the throttle. Makes me think that it is either a sticking idle actuator or MAF flap.
However, it starts up and idles ok (a little rough still, but is is 16 years old) when the ambient temp is above freezing or as soon as the engine warms up a bit. My thoughts wonder if there is a Bosch Motronic temp sensor somewhere in the system that is fried....
However, it starts up and idles ok (a little rough still, but is is 16 years old) when the ambient temp is above freezing or as soon as the engine warms up a bit. My thoughts wonder if there is a Bosch Motronic temp sensor somewhere in the system that is fried....
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Pro
Joined: Jan 2005
Posts: 701
Likes: 6
From: St. Albert, Alberta, Canada
Searching the PET for temperature sensors I've found many:
2 on the breather cover
1 on the oil pressure sensor cover
1 on the chain end of the case
1 in the cylinder head (which I think is the Motronic sensor?)
1 in each chain cover
Thats "only" 6 in total (not including the ones in the HVAC and the oil cooler). Time for a rennlist search to see what does what!
2 on the breather cover
1 on the oil pressure sensor cover
1 on the chain end of the case
1 in the cylinder head (which I think is the Motronic sensor?)
1 in each chain cover
Thats "only" 6 in total (not including the ones in the HVAC and the oil cooler). Time for a rennlist search to see what does what!
Addict
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Joined: Jul 2003
Posts: 2,577
Likes: 52
From: Atlanta
The Hammer will give you a fault code on the CHT and most anything else that could be wrong. Read Garrett's thread on his car. I think he posted the resistance values for the CHT. My books are packed away still, so I can't look stuff up.
Pro
Joined: Jan 2005
Posts: 701
Likes: 6
From: St. Albert, Alberta, Canada
First off, Merry XMas to everyone and best of the holiday season!
https://rennlist.com/forums/showthre...ad+temperature
is a pretty good place to start as it has pictures (which are invaluable).
To summarize the post:
The cylinder head temp sensor, CHT, is a white 2 wire sensor in a 3 wire plug (the middle is blank) that hooks into the bracket at the fwd left side of the engine bay. There are three plugs on that bracket black, green and white with the white being the topmost of the three.
Testing of the sensor can be done on pins 45 and 30 (ground) of the DME under the left seat (thats the drivers seat in Canada) and should read as follows:
0C = 4.4 - 6.8 kOhms
15-30C = 1.4 - 3.6 kOhms
40C = 1 - 1.3 kOhms
80C = 250 - 390 Ohms
100C = 160 - 210 Ohms.
The only reason I summarize is that reading the post above had me confused until I wrote it all down.
FWIW, the great white north, or at least Edmonton, saw 8C today and light rain - so much for a white Xmas...I think my igloo has melted away!
https://rennlist.com/forums/showthre...ad+temperature
is a pretty good place to start as it has pictures (which are invaluable).
To summarize the post:
The cylinder head temp sensor, CHT, is a white 2 wire sensor in a 3 wire plug (the middle is blank) that hooks into the bracket at the fwd left side of the engine bay. There are three plugs on that bracket black, green and white with the white being the topmost of the three.
Testing of the sensor can be done on pins 45 and 30 (ground) of the DME under the left seat (thats the drivers seat in Canada) and should read as follows:
0C = 4.4 - 6.8 kOhms
15-30C = 1.4 - 3.6 kOhms
40C = 1 - 1.3 kOhms
80C = 250 - 390 Ohms
100C = 160 - 210 Ohms.
The only reason I summarize is that reading the post above had me confused until I wrote it all down.
FWIW, the great white north, or at least Edmonton, saw 8C today and light rain - so much for a white Xmas...I think my igloo has melted away!
Rennlist Member
Joined: Apr 2005
Posts: 372
Likes: 1
From: Houston, TX
Jeff - if mine has sat outside and the temp is south of 30deg about 50% of the time I need to fire her with no pressure on the gas pedal and then feed in throttle to hold say 1500rpm for about 30secs. After that she'll sit there and tick-over on her lonesome.
Since I couldn't find any record of the 02 ever being replaced at 155k miles I decided it was well past high-time. The new 02 has helped with cruise fuel economy by a few mpg, and now my cold-outside-morning startup has only needed me to add throttle when it's below 0deg F out there.
So your 02 might be a contributing component - but I would doubt root cause. I'd get up under the rear decklid and make sure the MAF is still tightly sealed between the airbox and the rubber hose going to the TB, as well as make sure your vaccuum line is still seated on the vac reservoir on the airbox itself. Un-metered air will certainly impact cold-start since the system is already adding lots of fuel to keep things going. With your lightened flywheel there combination of things is working against you in the cold - assuming I'm anywhere near the right track on this.
Since I couldn't find any record of the 02 ever being replaced at 155k miles I decided it was well past high-time. The new 02 has helped with cruise fuel economy by a few mpg, and now my cold-outside-morning startup has only needed me to add throttle when it's below 0deg F out there.
So your 02 might be a contributing component - but I would doubt root cause. I'd get up under the rear decklid and make sure the MAF is still tightly sealed between the airbox and the rubber hose going to the TB, as well as make sure your vaccuum line is still seated on the vac reservoir on the airbox itself. Un-metered air will certainly impact cold-start since the system is already adding lots of fuel to keep things going. With your lightened flywheel there combination of things is working against you in the cold - assuming I'm anywhere near the right track on this.
Thread Starter
Race Car
Joined: Nov 2004
Posts: 4,951
Likes: 1
From: Wisconsin
I may just relace the O2, but I do not have the lightweight FW; that I know of. Wish I had records from the PO. Thanks.
BTW- I still have that magnetic pickup- when are we getting together?
BTW- I still have that magnetic pickup- when are we getting together?
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Joined: Jul 2003
Posts: 2,577
Likes: 52
From: Atlanta
Hawk:
Don't replace the O2 sensor without checking it first. I could still be fine. Check the compression before replacing anything. You risk getting some bad news, but at least you don't spend a lot of money replacing parts that can't possibly fix the real problem. Good luck.
Don't replace the O2 sensor without checking it first. I could still be fine. Check the compression before replacing anything. You risk getting some bad news, but at least you don't spend a lot of money replacing parts that can't possibly fix the real problem. Good luck.