I had my alternator replaced and it's running real rough. I called the mechanic that put it in and he said the computer had to relearn everything. He said after cranking it 10 times it would go back to normal. Is this true? I don't trust this idiot, so I never know if he's telling the truth or not. Thanks, -Jeff

 

The pcm does relearn strategy when the battery is disconnected but it's never so bad as to cause it not to start or run so badly you'd notice or be uncomfortable driving it down the road. More than likely, he knocked a vacuum line or a spark plug wire off. Take it back and make sure he at least takes a look under the hood. He'll probably slap himself because it's something silly he should have caught before he gave it back to you.

 

My wife said the van actually runs smooth when going down the road. It just idles rough. When you go from Park to Drive the lights will dim and the rpm drops from about 800 to about 500. But going down the road it runs better than it ever has. It has a lot more power. Before this happened, I put a used motor with 90k miles, a rebuilt transmission, and a new computer in it. The transmission is a "beefier" transmission than what it had originally. It was acting up and then the alternator died. Also when you turn the steering wheel sharp it shuts off. Just thought I'd give more details about what I have. Any advice would be great. Thanks, -Jeff

 

With the added info, it sounds like you may have an IAC valve going bad. If thats the case it likely wasn't caused by the alternator being replaced. What the IAC does is allows air to circumvent the throttle plate and adjusts itself through commands from the pcm to maintain a steady idle. If the power steering causes a large drop in rpm, or any other loads for that matter(trans engage, electrical loads, AC compressor) it often points right to that valve.

 

Thanks for the info. I replaced the valve and it's running better than it ever has! -Jeff