Limp Home when hot...please HELP!!

[explorerjohn64]

My 93 explorer runs great while cold. Worse when warm, and almost like a limp home mode when it reaches normal op temp. There are no codes, no light, even though it does work.These things I have already checked/cleaned/replaced...etc

Thermostat
MAF
TPS
COIL
Fuel pressure
plugs
vacuum leaks
air filter
fuel filter

Checked Cat with a temp gun... seems okay. Again, it runs great when cold... no sign of problems. Any advice?

 

[unclemeat]

Was the thermostat installed correctly? Was the correct thermostat used? There is an air release valve on the thermostat, and it must be installed at the highest point.

 

[explorerjohn64]

At this point I can only assume it was the right one. It looked like the one I took off. If there is a valve, as you say, then it's not correctly installed. It didn't appear to have valve, I'll check, thank you.

 

[explorerjohn64]

okay, so far.... went to check air release, found that the failsafe therm I installed had failed open. Changed to a stant, air release at 12 o'clock. Thinking that possibly my cat may be bad even though not super hot, disconnected exhaust from cat back. Without failsafe it is registering running hotter, but still well within normal. Still runs great when cold, changes when hot. No sign of blown gaskets. No codes. So far... New coil, plugs, wires, MAF, thermostat. TPS seems okay. CPS a possibility without a code? I'm also wondering if it's a bad wire somewhere, there have been times when it runs just fine. That would be a mess to track down though.

 

[explorerjohn64]

Final problem

I'm posting this for any that may be having a similar problem. The original problem was chugging/no power after driving a bit. Seemed heat related. My service engine light works, but gave no codes other than MAF, which I replaced. So I ran a fuel pressure test and it checked out fine. I replaced the coil, wires, plugs, CPS, TPS, cleaned the IAC, finally... even though it checked out okay, I dropped the catalytic converter. No change.

Now here is what 3 weeks and lots of money and cussing taught me.

Never... and I mean never.... do a pressure test without driving. You can brake torque all you want, it's not accurate. So I do one last fuel pressure test, I snake the gauge up through the hood to my windshield, make sure the line doesn't get pinched to hard when you close the hood(only to safety latch). Now, drive until it acts up... And there it is.. pressure drops from 34 to 10. Regulator works, new fuel filter doesn't help, no pinched lines... you guessed it... a fuel pump that looses pressure after it heats up under load.

SO... I spent around 600 to fix this myself and learn this lesson. The good news is I have a lot of new parts that I don't have to worry so much about in the future, a tune up, and a fuel pump, all for about the price of having a garage fix the pump anyway. Any education worth having is worth paying for anyway!! LOL

My thanks to all who helped on this, and also to Burns for the photos of fuel pump location through floor. http://www.explorerforum.com/forums/showthread.php?t=182160 I sorta used it with a twist... I'll comment there.