74 911 runs rough in morning...help

Elu · 10-24-2005, 08:09 AM

My '74 911 runs really rough in the morning....especially when the temperature at night drops into the 40's and lower. It runs like it's missing and the RPM's go up and down, never consistant. After it warms up and I shut it off for a little while I can get back in it and it runs superb.....

My thoughts is that it's the warm up regulator....or are my injectors clogged? It would seem the injectors would be fine since it runs well when warm. I noticed someone installed a 1980 warm up regulator on my car. I want to change it back to the '74 regulator, could this be my problem?

Any thoughts would be welcome.

klaucke · 10-24-2005, 08:35 AM

74 WUR's are NLA and not externally adjustable (they may not be internally adjustable either, I'm unsure. They don't come apart easy regardless). It could be your WUR, or your Cold Start injector could not be functioning properly. Perhaps see if this 7th injector is working, you can always adjust the WUR. A search will yeild threads on how to do this.

Elu · 10-24-2005, 11:36 AM

bump

Rex Walter · 10-24-2005, 12:34 PM

ELU,

Did it always run like this, or did this start recently? It could be your WUR. The cold start injector only runs if the car is cold, and the starter is engaged. If the car starts at all, the injector is probably working. If the injector continues to run, or if it leaks, the car will run way rich.

Do you have a pop-off valve? Could it be staying partially open in the cold? A vacuum leak can also cause some poor running symptoms.

Rex

Paulporsche · 10-24-2005, 03:35 PM

Sounds like the WUR. Your cold control pressure is most likely too high, leaning your mixture. You need to check it w/ a fuel pressure gauge. The 80 WUR may work. It may just have to be set differently from the 80 cold spec.

Also, you may find an earlier WUR w/ vacuum and atmospheric ports may work better to provide enrichment changes @ WOT or for high altitudes, since the 80 operates using input from the O2 sensor. On the other hand, this may not be an issue for your condition and driving habits.

As mentioned, you should also check for air leaks.

Jubbie · 10-24-2005, 08:52 PM

My 77 C3 engine did the same thing cold. Ran fine warm, just like crap cold. It was one of thoes external adjustment do it your self mod at home type of WUR and I could never get both the warm or cold setting right at the same time. So I put a new one in. It works like a top now. I would think that a 77' WUR would work just need to tap into the vacuum line that runs to your dizzy and disable the throttle switch.

Elu · 10-25-2005, 07:06 AM

Great...I appreciate all the input. My car has been getting progressively worse as it gets colder at night. I live in Albuquerque. The summer is hot, the nights are warm, the fall hits fast and the winters can be unbearable at times. Mostly we see mid 50's at the lowest, but at night it always drops into the teens and twenties.

I just want the car to run well in the am. Nothing like driving it to work and having it chug and cough all the way there.

Thanks again...