QuestionHi dave , I own an 86' porsche 944 n/a and am having a problem that neither I or a friend who is porsche tech. can't figure out . I have been using clarks garage.com for tech info. and has proven to be a good source but no one on the message board can seem to help . Anyways heres my issue :
On cold start-up the car runs rough with an eratic idle ( sometimes I have to lean on the gas to get her going ) After about 5 minutes at idle it will finally run smooth . As I proceed to drive and car gets up to temp. I come to a red light and the idle climbs to 1200rpm . A mile later at next light its up to 1400rpm . At this rpm for any lenght of time the car wants to over heat . So I hit the a/c button , the fans come on , temp. drops , and idle goes to 1100rpm . If I have to do some city driving I unplug the o2 sensor and keep the a/c on .
I have test almost all the sensor on the car ( mass air , tps , dme stuff ) . Not only did the test check-out but everthing was clean inside . All vaccum lines have been inspect , idle stabilier replaced , old o2 was good but installed another one anyways ( 60k), no intake leaks .
Any ideas on what it is that Im over looking ?
AnswerHi Paul. Running the A/C and unplugging the O2 sensor...now that's creative!
There are a few areas that could be your trouble spots. I'd suggest these:
1. The engine coolant temp sensor. Test this at the computer,,,terminal 13. Below 175 degrees the resistance measured in ohms between term 13 and ground should be1.45 to 3.3K ohms. Over 176 degrees, the resistance should be 280 to 360 ohms.
2. Check for "false air", meaning air entering the combustion chambers without being measured by the airflow meter. This can happen on the 944 at the connector tube between the intake manifold and the airflow meter itself.
3. If you haven't flow tested the injectors, do that too.
Good luck. Let me know how it turns out.
Dave
