Ugh...Cold Idle Surging...
03-20-2017, 03:28 PM
#17
Rennlist Member
Resurrecting this thread. Did anyone here actually come up with a definitive answer for the idle surge at startup problem?
I'm having this same exact issue with my N.A. 1986 944. I don't remember this happening until it had been sitting for a while this winter. Now, when I start it up it almost dies, then surges back to life over and over until I rev it up a bit for a couple of minutes.
I guess I'll start with the easiest solution first - new temp sensor and go from there?
I'm having this same exact issue with my N.A. 1986 944. I don't remember this happening until it had been sitting for a while this winter. Now, when I start it up it almost dies, then surges back to life over and over until I rev it up a bit for a couple of minutes.
I guess I'll start with the easiest solution first - new temp sensor and go from there?
I don't believe there is one in a normally aspirated engine like yours ...
The solder joints were loose and had to be re-soldered
Tom M'Guinn to the rescue !!!
Regards
Ed
03-20-2017, 06:30 PM
#18
Rennlist Member
03-20-2017, 06:49 PM
#19
Rennlist Member
03-21-2017, 01:12 PM
#21
Rennlist Member
03-21-2017, 05:15 PM
#22
Burning Brakes
after having the same issue the past few weeks my conclusion is leaking injector/s and possibly the fuel pressure regulator ( FPR) also.
When the engine receives a rich mixture at idle when cold, the ECU corrects the rich mixture by increasing the air flow through the Idle air control valve but the correction is usually an overcorrectlon so the ECU reduces the extra airflow through the idle air control valve which sets up a constant fluctuating idle.
The additional fuel that is causing the over rich idle mixture is probably due to either a leaking FPR leaking fuel into the vacuum system or leaking fuel injectors.
If you start the car and pull of the vacuum pipe from the FPR and damper you can check to see if either are leaking fuel into the vacuum system. If they are ok then a fuel pressure and leakdown test should narrow down the cause of the issue
When the engine receives a rich mixture at idle when cold, the ECU corrects the rich mixture by increasing the air flow through the Idle air control valve but the correction is usually an overcorrectlon so the ECU reduces the extra airflow through the idle air control valve which sets up a constant fluctuating idle.
The additional fuel that is causing the over rich idle mixture is probably due to either a leaking FPR leaking fuel into the vacuum system or leaking fuel injectors.
If you start the car and pull of the vacuum pipe from the FPR and damper you can check to see if either are leaking fuel into the vacuum system. If they are ok then a fuel pressure and leakdown test should narrow down the cause of the issue
