4.0 problem

[AKBroncoII]

I am looking at getting another explorer. The problem is, the current owner says it runs great until you give it some throttle. Then it falls on it's face and dies. Any ideas? It's a 91. I can pick it up for a decent price. Just don't want to get anything that is going to take a lot of work.

[Wicked_Sludge]

thats a pretty broad symptom. your going to have to do a little digging into it to come up with possible causes, such as checking engine vitals (compression, fuel pressure, oil status, and most importantly pull the codes)

[oldmantruck]

I had a 92 that acted like that, turns out it was a burned exhaust valve completely killing a cylinder. for an easy check, hold a dollar bill to the exhaust and see if it gets sucked up the exhaust pipe. the dollar should flap along happily, if a valve is burned( exhaust only) it will suck back up in when you get to that cylinder. I would also code out the PCM (or what ever they call it on OBD1) It only takes a jumper in a 91, instructions can be found on autozone.com under repair guides for the vehicle. A compression test is also good if you have time and don't mind trying to get to the plug behind the a/c . I had a failed transmission modulator on the same truck, pull the vacuum line from the transmission and look for oil. Good luck