skipgresham944

My 90 944S2 has developed a cold start problem - I don't need this right now! For a while, it would run very rough/stumble if revved above about 3k rpm when cold. Once warmed up, it would run perfectly. Now, it runs rough and stumbles whenever started when cold.

How does the cold start system work on these cars? There is a fifth injector connector that attaches to what looks like a vacuum control switch near the fuel rail. Is this a cold start injector?

The problem did not occur before the intake manifold was removed and replaced after cleaning and painting. The spark plugs are pretty new. What's going on here - ignition problem? fuel system? Thanks much SG

Jfrahm

Sounds like a temp sensor might be disconnected or broken. There are only four injectors, addl' fuel is injected through them for cold starts.

-Joel

skipgresham944

Which sensors/where do I look? Since this problem only occurs when cold, I certainly agree with you. I know the car mechanically PRETTY well but have never had to troubleshoot this type of problem before. I need this car to drive this week!!! AAUUGGGHHHH!!!

Kevin Baker

Two things you need to check. 1. The air temperature sensor. It is located inside the Air Flow Meter (AFM). Do a search on the archives for links to test procedures. 2. DME engine coolant temperature sensor. It is located above the upper balance shaft housing. Youll have to remove the intake boot to see it. It will be the one with the blue connector. There is a testing procedure someone posted a couple of days ago, but it only runs 37 bucks I'd just replace it. From the soud of the "stumble" around 3K I'd look at the first as the DME coolant sender only looks at water temp, and the AFM air temp sensor is used to determine the volume of air entering the engine.