Sputter, Stalling, Rough Idle, Dying when Hot

[PermafrostDan]

Hello, all, thanks for taking the time to read. I'm up in Fairbanks, Ak, having a heck of a time with my 91 explorer. It ran decent all winter in -50 degree weather, but since it's warmed up outside, it's been running awful. It start a week ago when we first his 70 degrees. After an hour of driving, when the engine was hot, I noticed it started stalling when I shifted into third. It got worse from there, quickly, and started idling really rough with the rpm going up and down, and then finally it got so bad that I had to pull off the road. When I tried to start it again the rpm would rev high (2k? I think) and then drop down below 800, stall, and die. This has happened a few times on warm days, but if I leave the truck alone for an hour or two to cool down it starts up fine and runs again without problems until it gets warm again.

From researching online, I'm leaning towards the fuel pump being bad, reason being that the pump craps out when it gets warm. Do you think I should buy a new pump and spend a day replacing it, or could it be something else I'm overlooking? I've recently replaced the MAF and cleaned the IAC. I did change the fuel filter yesterday and the gas that came out was pretty dirty. I've tried to run a pressure test but I can't find a place in town that sells a gauge for less the $50. I've heard that the FPR or the plugs and wires could cause similar problems, but would they also be affected by the heat?

Thanks for your help!

 

[Roadrunner777]

Fuel pump is quite likely. But, I recommend getting the fuel pressure gauge. It is one of two tools that get well used with 1st gen explorers. (The other is a code reader). If you have the time, you can get a gauge off amazon for around $30 with free shipping. Harbor freight has one for $20, plus shipping.

With what you have said, if I only had money for a gauge or a pump, I would buy the pump. Avoid Airpax products, they are known for limited lifetime.

 

[exploderguy77]

RR777---the exact same thing happens to my explorer too. have you found out exactly what the problem was? hope for some info

 

[Roadrunner777]

I have not noticed the problem lately. I'm not shopping at Walmart so much anymore, so shorter stops at other stores. See, I think parking in the sun with a hot engine really makes the underhood temperature soar.

If it were a carburated engine, I would be thinking hard about vapor lock. I don't know if you can vapor lock a fuel injected engine though... it seems to be like the pump would just flush the vapor back to the tank.

 

[Flip4ford]

I had the same thing happen it was droplets of oil getting on my air intake temperature sensor-- a new PCV valve and an air intake temp sensor cured the problem.