Hesitation at start [Archive] - SaabCentral Forums

: Hesitation at start


cghag1
05-06-08, 02:30 PM
My son has our '87 8V with him at school so we are trying to diagnose a problem long distance. Hopefully someone can offer some suggestions.

When starting the car after sitting all night or after work at the end of the day it will often hesitate, or bog down, when getting underway. Applying extra throttle does little to bring the RPM's up. After it warms up for a few minutes it will run just fine. Possibly related to this is the symptom that the car will not idle properly (too low) and want to stall right after starting up cold. The idle issue also goes away after having time to warm up. His problem is that he only has about a 5 minute commute to his job. So by the time it is warm he is pulling into the parking lot.

Any suggestions where to look, and how to test any possible malfunctioning part? My son has some basic tools available to him, and possibly a DVOM to test some components.

Thanks in advance,
Dave

Hu Flung Dung
05-06-08, 02:40 PM
Possibly the AAV (auxilliary air valve) which is located over by the thermostat...I changed the one in my 8V, not difficult at all to do.
First though take it off and spray it out with some carb cleaner and see if that helps. Good luck!

cghag1
05-06-08, 05:33 PM
Thanks for the reply. I've both cleaned the existing AAV, and swapped it with one from the junk yard (and also cleaned) with no noticable change in the hesitation issue either way. The idle smoothed out a little with less fluctuation but the problem was still present. Might the warm-up regulator be the problem?

jetman
05-06-08, 05:45 PM
Yes it could be the WUR or the temp send unit in the head. All three work together on the cold start process. It could also be bad cap/rotor/plugs/leads and it might be useful to clean the throttle body very well, clean and check the air flow sensor plate is clean and centered (under the rubber bellows).

cghag1
05-06-08, 07:06 PM
Thanks Jetman. I have previously cleaned the throttle body and checked the air flow sensor plate. The cap, rotor, plugs and wires were replaced within the last 6 months or there abouts so at this time I think I'll look at the WUR and the temp send unit. Is there a way to test these parts before swapping them out? If so, I'll pass the procedure along to my son and have him perform the test.


Thanks again guys!
Dave