More on 98 DeVille no start issue
 

Back in August, I posted about a 98 DeVille Northstar that would crank and fire but immediately shut down. Was finally able to look at the car in person a couple weeks ago, drive it to my shop and also have a mechanic buddy check it out.

At first, the engine started and ran a little bit then quit as she told me. Restarted and again did the same thing. On third restart, engine ran longer but rpm cycled up and down several times before stopping again. The forth time, we decided to manually hold a higher idle using the gas pedal and after a minute or two of warm up, the engine idled down normally and the car was drivable.

Drove the car to my friend's shop the next day where he checked the computer codes. He said there were several codes but nothing that would have caused this condition. He cleared the codes, started it several times and the check engine light stayed off. Got it back to my shop and put a battery charger on it for a whole day.

It started and ran normally a half dozen times after that over a few days. I parked it outside overnight when temps reached single digits by morning. It cranked and started normally but soon died. It acted like it wasn't getting enough fuel. Restarted and it ran rough for a few seconds, then straightened out. I drove it a minute or two later and it ran OK.

Left it outside again in the cold and upon starting the next morning and it kept running although rough but soon smoothed out and could be driven normally in a few minutes. When this starting problem occurs, it doesn't seem to matter if it's warm or cold outside but obviously the engine warms up faster in warmer temperatures.

A suggestion was made a couple of months ago that the idle speed control unit might be bad or in need of cleaning. Does anything I have related here lead anyone to confirm that? Not even sure where this part is located on the throttle body. Not sure why the car would run perfectly one day and have trouble starting the next.

I wasn't able to access this car for a couple of months but now it's in my shop and in my way. Need to get it so it will start and run with some degree of confidence for the owner. Any other suggestions out there? Thanks.