M wife and I have a '91 explorer that recently had a tune up (4 months or so ago). The truck has about 150k miles but the motor was a rebuild (Jasper) about 40k ago.

The problem we are having is this, when we first start it up (usually in the morning) it idles fine both in park and in gear. When we try to accelerate the rps drop down very low and the truck will either die or catch itself and then go. It also does this if we end up at a stop light or stop sign in the first few minutes of driving. Once we get past that initial acceleration it drives fine, and after a few more minutes we can stop and go with no problems. The truck will sit all day while my wife is at work and when she gets out to come home she does not have any problems. But the next morning the same problem all over again. I don't know if it is a "cold" weather related problem because we live in Florida and the typical low temperature right now is about 40-50 degrees over night.

Any suggestions or ideas?

Thanks,
Worgus

 

Hi, I'm new to the forum, and was about to post when I came across your post. I also have a 91 Explorer, with the exact same problem. Did you ever get any replies or find a solution to the problem?

 

Nothing yet. I tried the Fuel Filter and tried running some injector cleaner... nothing has worked thus far. It has also developed a strange leak of coolant... so now i am really stuck...

 

I had a similar situation occur on my 94 Ranger 4.0; it idled great when warm but try to accel from a stop and it fell flat in it's face. It was, for about 99.99% of the people in this country, undriveable. Outside temp was around 65-85 degrees F. I pulled the codes and the IAC solenoid and MAF sensor were flagged. IAC, you just gotta be kidding I thought because it started and idled great. But in the end, that was the problem. There are pinpoint diagnostics for the IAC; myself I'd start by pulling the codes on your Explorer as well as checking fuel pressure.

BTW, my first reaction to the prob was fuel filter or maybe fuel pump. I replaced the filter and it didn't help. Yeah, it acted like fuel starvation and in the end it was a lousy solenoid that is supposed to control the idle. Funny how it all ended. If the IAC is your problem, clean your MAF anyway; if it hasn't been done it will probably need it before long and it's really easy to do.

On edit: the IAC can be cleaned; in my case the diagnostics were to clean and try the rig. If the problem persisted and the code was flagged (and in my case they were) replace the IAC solenoid.

 

i had the same problem when i just got my 92 exploder. i changed the plugs and the wires it solved the problem, i would check to see if jasper put new wires on. everything else was fine. idle and accelerating slowly, but when i tried to punch it it coughed alot. good luck