Stumped... please help

[explorerjohn64]

Originally I thought this was temperature related. I have changed my mind.

93 ford explorer, idles fine, accelerates fine as long as it is in park and not moving. It ran 45 minutes this morning with no misses or acceleration trouble while I ran tests. Took it out on the road, gunned it, 0-40 quickly, then went into what I call " limp home mode". At this point (after drive) it doesn't even idle well in park, and when revving engine in park it stumbles around 2500 rpm, sounds like it is gasping for air, almost like a stuck choke. Shut it off, start it immediately back up and it is fine. Take on road, 0-40 then stumble, limp home, same cycle. Runs great as long as I don't drive it over 35-40.

It is throwing no codes.
NEW....
MAF
air filter
thermostat
coil
plugs
wires

Compression, vacuum, and fuel pressure are fine. Cat is not clogged.
Any help would be greatly appreciated.

 

[lounge lizard]

how do you know the cats are not clogged??

 

[explorerjohn64]

they temp check okay, back pressure okay, and still not believing, i removed them... no change. Also, TPS checks out okay. I am wondering about CPS, but baffled as to why load/speed make a difference.

 

[lounge lizard]

well that is why I question the cats.

at low speed there will be normal back pressure on the motor. but as you pick up speed the pressure builds and that is when you feel the drop of the motor. and the limp home mode sets in.
then when the system has had a chance to expire the extra pressure, it starts right up and runs normal.

so the cats may not be fully plugged, but the restriction is enough to show up when under load.

 

[explorerjohn64]

Yeah, I thought the same thing which is why I took the cats off, still does it. Today I replaced the crank sensor... no change. Cleaned the IAC, no change. Thinking perhaps my readings could change with temperature I replaced TPS.. no change. Tomorrow I'm gonna change the ECT, although I've never had this kind of problem from that, seems possible. Does anyone think this could be torque converter related without a light?

One more thing.... even though this thing will go 0-75 just fine, then start to sputter to the point of no power, if you pull over, shut it off and immediately restart, it's back to fine for a minute or two of driving. If you don't put it in gear, it's perfect for eternity. Could it be TC lockout circuit related?

 

[explorerjohn64]

Final outcome

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.