I was running my newly built and installed engine this afternoon because I replaced the battery and wanted to make sure it had a good charge. It was running about how it usually does, I had It at about 2000 rpms for a little while. All of a sudden it dropped a hundred rpms for a half a second and continued to run just fine. About ten to fifteen seconds later it did the same thing but dropped like 400 rpms. Then about ten to fifteen seconds later it just completely quit. It didn't stumble to a stoP it was like someone turned off the key. And the check engine lift came on. I thought it was strange so I got out checked under the hood everything looked fine. I tried starting it again and it cranked right up and ran fine, no check engine light. Any ideas?

 

Hmm. loose wire, or bad sensor.

 

Are there any codes stored?

 

That CEL should be stored now. You should pull it and see what it is so you have a good idea of what you're dealing with.

What would be helpful if you gave us specs. What year, engine, tranny, etc?

 

make sure your grounds are tight and make sure youre battery cables are tight. same goes for alternator and starter.

mine did something similar and it was a loose ground on the firewall.

 

Sorry I thought I had put up all the details. It was kind of late last night. Anyway. It's a 2000 xj with a 4.7L Stroker, auto trans. I had an idle issue right off the bat, I ran my cam break in procedure and the computer seemed to settle down and it corrected itself. I had the battery out for a bit when I replaced it so I was thinking it may have to relearn it again. it really felt to me like a loose wire or bad connection somewhere. Temp was good. Oil pressure is good. Not sure what's up. I will try and pull that CEL code and see what it says.