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cold start problems

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Nick Neves  

PostPosted: Sun Aug 26, 2001 8:49 am    Post subject: Reply with quote

hi gang. for a while now, my 1981 931 has started kind of hard, rumbling and sputtering and then finally picking up and smoothing out into a normal cold idle. it began to get progressively worse, until i needed to pump in some gas right after start up to help the engine over come the roughness without dying. now the thing won't get past that roughness-- it may try to run for a second or two, then just stumbles and dies. this is only a cold start problem and does not occur on warm starts. the engine runs perfectly other than that. okay wise sages of the 924, what should I look at first? cold start injector? warm up regulator? kanuter valve? thanks for any's great to have a resource like this on the web where we can all benefit from each other's experiences!
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PostPosted: Mon Aug 27, 2001 4:51 am    Post subject: Reply with quote

WUR is shot.

if it runs hot ok that is.
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PostPosted: Wed Aug 29, 2001 5:58 am    Post subject: Reply with quote

Check the thermo-time switch first. Make sure it is supplying ground to the cold start valve for 10 seconds when you crank your cold engine. Check the cold start valve to see that it is supplying fuel during cranking. Check the aux-air valve to be sure it is fully open when temp is below 60 degrees F. If these are OK, then check WUR.
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Nick Neves  

PostPosted: Fri Aug 31, 2001 5:28 am    Post subject: Reply with quote

hi guys, i checked the WUR by looking at the ohms across the terminals, 24ohms consistant, so that checked out ok. a bad one will register infinite or 0... about 20ohms constant is what you're looking for. next i popped of the auxiliary air valve and lo and behold, the disc thingy was nearly closed and my engine was plenty cold. bingo. i ran current to the plug and watched; the disc should rotate from fully open to fully closed over the course of about 5 minutes. mine went ot 85% closed to fully closed in 1 minute, so it's bad. Thanks for the posts guys, i appreciate your help! side note--the warmup regulater in my 931 has a vacuum line going to it and is taller than the part number that NAPA and other parts stores gave me. they had me listed as needing a ...011 Bosch number, I really needed an ...091 Bosch number part. apparently, mine's a lot more expensive, too. if anyone knows what that vaccuum line is there for, and if it's okay to just use the one without a vaccuum line, i would be interested to know. thanks!
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PostPosted: Fri Aug 31, 2001 3:34 pm    Post subject: Reply with quote

The vacuum line allows the WUR to reduce control pressure at wot. This allows a richer fuel mixture when you need it. If your aux air regulator is bad, holding the thottle partially open will allow your car to start. From your description it doesn't sound like this helped. The closer to 100F air or engine temp the more the air regulator will normally be closed and the shorter the time to completely close. What was the outside temp when you checked yours?Recommend you check the thermotime switch and cold start injector as mentioned earlier. Good luck

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PostPosted: Sat Sep 01, 2001 3:27 am    Post subject: Reply with quote

oops i musta read your first post too fast Nick, once the car is started, if keeping the pedal down a little bit helps the car run and smooths everything out, then the aux air is bad.

I've got one BTW if you don't wanna pay for a new one, im not sure how much they cost new...

The line that goes into the WUR is for when u have boost and need the extra fuel.
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