My 964 will not start back up if warm or hot shortly after turning it off, it will start back up if you wait a bit. approx. 10 - 15 min. I have searched all the info I can & have found posts that involve 964's that are hard to start when warm but none that won't start at all. What I am thinking is that it may be the Head temp. Sensor. It seems that when the Head temp. Sensor fails it usually involves cold start issues, however my car starts fine when cold. The 02 sensor is fairly new & it is my understanding that the 02 sensor is not involved with start up. I don't believe it is the DME relay as my fuel pump is running when the car won't start. If anyone is familiar with this I am just wondering if I am on the right track, starting with replacing the Head Temp. Sensor to solve this problem.
Thank You

 

Alan,

I have a similar problem with mine but have not yet solved it - changing the head temp sensor did not fix it.

With mine if it is HOT (ie. 30 - 40 minute track sessions) not just warm it runs great. Once I shut it off, it is a bugger to restart. Once it is coaxed back to life, it is almost like is is misfiring or running on less than 6 cylinders - definitely down on the power too. After running for a few minutes, the problem usually clears and it runs fine again.

I would be interested to hear a fix for this too but the temp head sensor did not fix it for me. YMMV.

Marc

 

Have you checked the ISV?

There is a read-out on the Hammer for the IACV (Input Air Control Valve) which registers percent (open?).

The idle switch position can be read, as well.

 

I have a hard starting problem when warm/hot as well. Just read last night that it might be the Evaporative Emmission Control unit or "Charcoal Canister". Apparently that creates hard starting when hot.

Still working on oil leads so I won't get to this for a few weeks. Can't confirm that it fixes the problem.

 

Thank you for the replies. I have checked & cleaned the ISV, checked with 12 volts, it flutters, the car seems to idle fine but it is possible that it is off a bit on hot start up. I also checked the throttle switch, it is closed during idle & start up, I have disconnected it at idle & the idle gets rough so I guess it is working correctly. I suppose there are many possibilities for this hot / warm start condition & I have checked the usual suspects. I may try the head temp sensor, I believe there is a way to test it with an ohm meter. I have a feeling this may be a hard problem to pin down. Thanks again.

 

Note: The temperature sensor II informs the control unit about the
cylinder head temperature. It is responsible for mixture enrichment
for cold staring or warming-up.

Break (infinite Ohm):

The DME control unit of the Carrera sets itself to a fixed resistance
value permanently stored in the control unit which appriximately
corrsponds to that of an engine at operating temperature. There is
no enrichment by the faulty NTC II when the engine is warm (emergency
running program). This results in starting problems i the engine is cold (no cold start enrichment).

Short-ciruit (0 Ohm):

In cold state, no engine pick-up, too lean, and engine stops.
No effect if engine is at operating temperature.

 

I need to chase the engine temp sensor for my other track car that has a cold start problem. Question for those that have run this test. If the resistence checks out OK at room temp is it generally OK throughout the temp range?

How do you test for the hotter ranges? Run the car to get to temp. Turn off car and then pull the DME plug to take readings? Probably the logical answer.

Thanks

 

Put it on the stove in a pan of boiling water and check the resistance values.

Marc

 

long time ago, but did you fix the problem? I have the exact same symtoms on my 964rs.

jonas