CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

2002 Buick Rendezvous has random stalling

I have a 2002 Buick Rendezvous with a 3400 sfi engine. The vehicle runs perfect except random stalling when you are stopping or pulling out. It seems the vehicle has a random low idle unless the air conditioning is on at which time the idle stays around 700 and the vehicle does not stall. I had a repair shop clean the throttle body which made no difference. I replaced the IAC valve and air filter yesterday and still no change. Also was wondering if you unplug the IAC valve should the idle change because it has no effect on the idle at all when I unplug it while the vehicle is running. Thanks for any advice possible. Really cant afford to just start replacing item after item with no result.

Sounds like my Chevy PU from last year. Fuel pump. When it’s going out but isn’t quite dead it will run weak at times causing the stall. It will also struggle when under a load like “pulling out”.

Thank you. I guess you have to check the fuel pressure ?

They suggest you do (but I think it’s a lot of hassle.) Could be inconclusive if your is “going out” because you may test it while it’s working. Of course, if you test it and get low pressure then you know the problem. Most auto parts stores will loan you a pressure testing kit. It will probably take you 3 hours if you haven’t done it before.

Unplugging the iac does nothing? Even the new one? Also check for vacuum leaks. You can carefully spritz some wd40 or starter fluid around vacuum lines to see if idle is affected. If you notice that the idle briefly picks up when ypu spray on a particular spot, inspect that hose for cracks.

RemcoW:
Yes even the new IAC when unplugged does nothing. Wasn’t sure if it should or not. I would think it should change the idle somehow. Other then the low idle the car runs perfect. No rough idle or anything.

The idle should change but maybe the computer has detected some sort of massive vacuum leak and has turned the IAC off to make up for it - that’s basically the same as unplugging it. I’d inspect for air leaks, like I suggested above. Vacuum leaks will totally mess the system up.

RemcoW:
Thanks for all your help so far. I will look for vacuum leaks this weekend and let you know what I find. What you are saying sounds totally possible. Thanks Again !

RemcoW:
I could not find any vacuum leaks so far. I am going to put a new TPS on it this weekend. Do you know if I need to disconnect the negative battery cable before I change the TPS ? Some have told me yes and some have said it is not nessary. Thanks

RemcoW, I have the same car with the exact same problem. Did you ever find a solution?

Thanks!

RemcoW, I have the same car with the exact same problem. Did you ever find a solution?

Thanks!