1991 Cad Deville - 4.9L Idle Speed Mtr Clicks?

GFORCEAUTO · Post by **GFORCEAUTO** » Tue Dec 15, 2009 7:07 am

ok guys 1991 Cadilac Deville 4.9L B engine with the idle speed control motor. Does anyone know why the idle speed motor clicks after turning the engine off? Customer brought us this car after several shops have messed with it. Oh boy!! Now we have to be the heros. This car is not in our wheel house of knowlage. I never saw many Cadillacs working at a Chevy dealer. Does anyone know how to set the base idle and adjust the idle speed control motor? That would help up out alot. Thanks In advance!

steven kiser · Post by **steven kiser** » Wed Dec 16, 2009 3:08 am

do. do. do. do. do. do, warning will robinson.

these beauties are a very very touchy. when the key is turned off the computer goes through a series of shut down steps. usually when the idle control starts clicking it's because the computer is searching for a tps signal. i'm surprised the a/c compressor isn't doing the same thing. in some instances it engages during an anti dieseling program. now, you will need special tools to properly set the idle control. there are more than one setting on this switch. base, cruise, climate. also this switch acts as a decelerator. when your cruising along at speed above 30mph (i think, not 100% sure on speed) and take your foot off the gas it will slowly back off on the throttle plate. if it didn't the car would nose dive because of the ratio of the transmission. it would be like going 30 in a standard in second gear and taking your foot off the gas. getting scared yet? should be. to repair it properly you need a tool to plug into the switch, an ohm meter to read the tps, feeler gauge, and a vac plug (i think, not completely sure on the vac plug. been a while). if you decide to lay a hand on this trying to repair the problem there is a possibility there is a vac leak causing a stall and some rocket scientist took a pair of pliers and screwed with the adjustment. you may even see where the bracket was bent forward instead of the solenoid being attacked. my advice grasshopper is to sprinkle holy water on it and call it a day. this car was created by a descendant of dr. frankenstein and shows it. personally i'de tell the customer if that's his only issue to consider himself real lucky. screwing with this can be the door to hell if you've never had the pleasure to live through these when they were popular. if you decide to work on it please explain to the customer all i've said because most likely the issues that will pop up will make pandoras box look like a trip to the park.

GFORCEAUTO · Post by **GFORCEAUTO** » Wed Dec 16, 2009 7:34 am

You are correct sir hahaha said Ed McMan to Johnny Carson. Some long eared dude (that would me Mickey mouse)has taken the pliers to the Idle motor and replaced the tps. OH joy! We found the settigns off and reset the base idle and Idle motor Correctly !! That was fun... we also found 5 out of the 8 injectors having high resistance. Recomended all 8. We told the customer there were other ways repair the injectors but we would NOT do the job unless he replaced all 8 at the same time. Thanks for the help