Questions and Answers

Buick Riviera Surging Q. I have a 1995 Buick Riviera. it has a 3.8 liter supercharged engine that is backed by an automatic transmission. The car has been good to up till now. It just hit 120,000 miles today. The car is fuel injected. I am having problems with the car surging at idle in drive or reverse.

The entire car "hops", the engine moves as though it is going to break free. From reading articles from your site I decided to change the EGR valve and oxygen sensor. A local shop gave me a diagnostic for $60.00. The results came back as follows Codes: Quad Drive motor, O2 sensor low, EGR pintle position error.

This was performed on a Snap-On 2500 diagnostics machine. The shop informed me they would have to do more work to find out what was causing this problem ($60.00 more) This problem only occurs after the check engine light comes on. This happens when the car has been warmed up for five minutes or so. Since this problem started the car has started to run hotter than normal. Do you have a helpful suggestions?

Sincerely,
Ryan

A. I would go see a dealer for this problem. The quad driver code is the most likely problem. A quad driver is a device inside the computer that is in control of 4 devices. If one of them develops a short or open, the ECM monitors this driver and shuts it down for protection. The other codes could all be on this driver and any one of them could be the culprit.