‘87 944 NA Rough Idle on Startup
05-28-2020, 05:54 PM
#1
2nd Gear
Thread Starter
‘87 944 NA Rough Idle on Startup
Hi there,
I’ve seen some similar threads to this, however by following them, I still have been unable to resolve this issue. Please note that I have read all of those threads, so this is not meant to be redundant.
Upon an initial startup, my 944 idle bounces, but stabilizes about 15-30 seconds later. This has come about after a plethora of fuel system work recently: a new gas tank, fuel pump, fuel filter, rear fuel hoses and lines, DME relay, and some new vacuum hoses. This issue came about about a few weeks ago when we found a vacuum line to the FPV was burnt to a crisp. We then replaced it and the problem seemed solved (no rough start at idle). Recently, the issue has resurfaced with nothing visibly wrong anymore. Unfortunately, my tachometer doesn’t work as well, so I’m unable to tell you the exact rpm during the rough start (if you have insight into why every gauge but the tach would work, that would be appreciated too). I’m thinking maybe replace ISV? It seems to be the only pertinent part that I haven’t yet replaced with something brand new. Insight would be appreciated.
I’ve seen some similar threads to this, however by following them, I still have been unable to resolve this issue. Please note that I have read all of those threads, so this is not meant to be redundant.
Upon an initial startup, my 944 idle bounces, but stabilizes about 15-30 seconds later. This has come about after a plethora of fuel system work recently: a new gas tank, fuel pump, fuel filter, rear fuel hoses and lines, DME relay, and some new vacuum hoses. This issue came about about a few weeks ago when we found a vacuum line to the FPV was burnt to a crisp. We then replaced it and the problem seemed solved (no rough start at idle). Recently, the issue has resurfaced with nothing visibly wrong anymore. Unfortunately, my tachometer doesn’t work as well, so I’m unable to tell you the exact rpm during the rough start (if you have insight into why every gauge but the tach would work, that would be appreciated too). I’m thinking maybe replace ISV? It seems to be the only pertinent part that I haven’t yet replaced with something brand new. Insight would be appreciated.
05-29-2020, 10:20 AM
#2
Instructor
I have been dealing with the same and have gone through a lot of different possible items with no luck yet. The only thing I haven't touched is injectors so I think you might want to look there.
However, if you get stabilization after coming up to temp, it might be that the cold resistance of the DME temp sensor is out of range. you can easily check it with a multimeter. Check Clark's Garage for the proper ranges.
However, if you get stabilization after coming up to temp, it might be that the cold resistance of the DME temp sensor is out of range. you can easily check it with a multimeter. Check Clark's Garage for the proper ranges.