Hello, I have been lurking here for a long time nad have always been able to find the answers I need, until now. I have had my 99 LHS since 2001, its been a really great car with very few issues.

For the last five years it had been relegated to "back up" car status, meaning we use it in the winter and when when one of the family is having car trouble. For the most part its sits in the garage covered up until its called on.

I went to get it out on Monday to clean it up and change the oil for winter duty, the battery was weak so I jumped it and it fired right up. I drove it about 50 miles to give the battery a chance to charge, it ran flawlessly as always. I took it back to the garage and changed the oil. The next day on the way home I stopped and picked up a new battery for it.

I put the battery in when I got home, any of you that have done that know how fun that job is, the car spun over great, the only problem was that now it wouldn't start. I tried again and gave it some gas, it fired right up and would run as long as I kept my foot on the accelerator and kept it around 8-900 rpm, as soon as I let off the accelerator it dies.

Even though the Check Engine Light I hooked my scanner to any way and it has no stored codes. Any thoughts on what this may be?

 

The computer lost its idle memory when you replaced the battery. That would be fine, but there is carbon build-up in the throttle body, which means the computer must open the Idle Air Control motor more than it expects to make the engine idle.

Two choices: 1), keep the engine idling with your foot on the gas, and slowly release the gas pedal. By taking sixty seconds or so to release the pedal, you give the computer time to keep adjusting the IAC steps up and learn the correct setting. 2), Clean the throttle body. Use a toothbrush, carb cleaner, and I think a mirror on this model too. This is the correct repair.

 

U replaced the battery it had to relearn what things were the IAC was set mechanically where the old PCM setting were U replaced the battery now they are all set back to factory.