[John V.]

My '99 Sunfire recently returned home, son had it for a few months out of town.

Has 129K miles.

It has started stalling. Son tells me that it was doing that maybe 2-3 times a week, then sometimes wouldn't happen again for a week or two.

Basically will just quit running while at idle. Seems to run normally on the road, including highway. Apparently ran fine on the 400 mile trip home. But sit at a light and it might just stop running (quietly, like you turned the key off). Or couple times, I got off the clutch and it either died or would start to buck like I was in wrong gear or not enough gas. Restarts without trouble and generally seems to idle normally. I took it to a shop, Check Engine light not on and mechanic said he checked history, no stored codes. Ran it for an hour and found nothing wrong. Paid the diagnostic fee and now trying to figure it out.

I cleaned the throttle body and the pintle on the IAC with spray cleaner. But it really was surprisingly clean, what little carbon & gum there was cleaned right off. Doesn't look to be the problem.

Put in new Autolite Double Platinum Plugs. The old plugs had 40K miles on them tops, standard Delco plugs, no fouling although I thought the center electrodes were fairly eroded. New Air Filter for good measure. Also found my Oil Pressure Switch was leaking oil (internally I think, saw oil in the connector) so I replaced that.

Started it up, idled smooth. Kept it running until it was fully warmed up, fan switched on. At that point, it seemed to be just fine. But then I opened the throttle while under the hood and it had a serious bog. Opened it a couple times in succession and the engine didn't want to respond and finally stopped running. Again, restarts without hesitation and idles until I open the throttle.

I did not take it out on the road yet. And I didn't open the throttle until after it was warm (still in normal range but above usual operating temp while moving). So I don't yet know if it is somewhat temp related.

I have a couple ideas. But hoped these symptoms would sound familiar to somebody here before I start throwing parts at it. I don't have a Scan Tool so I can't get test readings while it stumbles.

Anybody have a good idea what's going on?