CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Idle speed degrades in stop and go, causes stall when van warmed up

I have 2000 Grand Caravan w/ 3.3L, AT. When warmed up, in stop and go traffic, at lights, or in reverse for parking, the idle speed drops, the oil light flickers and unless shifted to neutral, stalls. I’ve replaced the fuel pump and filter. I’ve adjusted the idle screw on the throttle body to 700 rpm, where it stays when the van is cold or when stopping in normal driving. Someone suggested the oil pump, and I added motor honey, but no change in symptoms. There are no vacumn leaks evident. How do I keep the idle from sagging? Would this be a sensor issue?

It’s probably a bad Idle Air Control Valve. I would have a good, independent mechanic check it out. Newer computer control vehicles usually don’t have idle adjustments anymore since the computer controls the idle.

I cleaned the Idle Air Control valve and saw some improvement.
However, now the oil light starts ringing at 900 rpm when in stop and go traffic; instead of at 500 rpm.
The oil light still flickers and dings whenever I am backing in to a parking spot.
Any other suggestions, please?

Jeeze, the years are flying by. This vehicle is already 13 years old.
And how many miles does it have on it? How much oil does it use? How well has it been maintained?
I assume you checked your oil level?

The oil light is telling you that the oil pressure is dropping too low. If it’s flickering at 900 rpm, that suggests that the problem might bne normal wear. Oil pressure is created by the pump forcing the oil through small passages and channels. If the passages get too large due to wear, the oil can flow too freely through the passages and the pump have difficulty keeping the pressure up at idle. Soty of analogous to trying to keep a balloon with a pinhole inflated.

The oil is full. Sometimes on cross country trips, I need to top it off, but rarely between oil changes. It has only 304,000 miles - barely broken in compared to previous vehicles.

The stalling may not have been related to the low pressure-have you stalled since cleaning the IAC?

If you can, check the actual oil pressure-it may just be a sensor going bad. Mercifully, you’re having the problem at idle and not at 60 mph, so checking the oil pressure with a gauge is a bit easier :).