94 Explorer stalling

[wouldsman]

I'm back again, at your mercy & asking for help. Heres my problem: I've got a 94 explorer 4x4 w/ 5spd manual trans, 190K miles. It's always been a good runner, with the exception of the normal, minor things, which I've always fixed myself w/ the help of this forum. Anyway, all of a sudden, after warming up (its hot 100 degrees plus here)I'll be driving along and if I go to accelerate past 2000 rpm, it shuts down, let up off the gas and kicks right back on. Just like its running out of gas, except pumping the throttle wont keep it running, and it's instant. Happened to me 2 out of the last 3 times I've driven it and both times I've limped it home. Whats funny about it is that it's not over heating, needle's at normal 1/4 on the gauge and unlike most of the post I've read here researching, it doesnt idle rough, sputter, pop or backfire, push on the throttle and its just like turning off the key, let up, and its like turning back on, anything past about 1/4 throttle!
I have done nothing at this point, figured I'd run by you people before I did, in case anyone has had this happen to them. I should add that the 1st time it did this was a mile or so from where I was going and after about 30 minutes I started it up and drove the 6 miles home w/ out a glich. The next day made the 12 mile round trip, shutting it off for 5 minutes in town, w/ no problems. Next day went to town, shut it off for an hour, and w/ in 2- miles on my way home it started doing it, and that was yesterday.
Anyone had this happen or any idea what it could be or where I should start checking, fuel filter, pump?
I appreciate any input & thank you in advance.
Regards, Jerry

 

[vq5speed]

2 things could do what you describe. What you say engine power shuts down when you throttle it i interpret that as stumbling. Bad or going bad Throttle position sensor could do that. A bad or going bad Coolant Temperature Sensor can also cause this symptom. If the problem only seems to occur after the engine warms up I would lean more toward the Coolant sensor. Both these parts will cost about 35-40 dollars at Autozone

 

[wouldsman]

Is there any way to test the coolant sensor and shouldn't that trip the check engine light?

 

[natenkiki2004]

With the engine off and cold, unplug the sensor and connect a multimeter to it's pins. It should read a resistance pretty close to ambient temperature. Check this graph:

Granted, this is not the 'proper' test but it's quick, easy and gives you a general idea of whether or not it's failed severely. For example, my IAT sensor (which uses the same graph) registered to one of the extremes. You'll know it, it might show a few hundred-thousand ohms when it should be showing 25,000. Something like that.

 

[wouldsman]

I appreciate it, will give it a shot and see what happens...

 

[Bwana Bob]

I'm having the same problem: stalls or no start when hot. My favorite shop could not duplicate the problem. It runs fine for them and no codes. I believe that it is the crank position sensor. Any other sensor failing will make the engine run poorly but won't stop it completely. If the crank sensor goes, there will be no spark or fuel injection.

I'm going to check the wiring and change the crank sensor on Saturday. I'll let you guys know what I find, if anything.

Bob

 

[wouldsman]

Not the ECT

Ect checks out fine, 35.80 ohms, just to make sure I replaced it w/ the one off my parts rig and no difference. So I guess my next step would be the throttle position sensor, is there a way to test it? Also, is there any way the MAF sensor could cause this? Just seems strange that it only happens after the rig reaches normal operating temps. Any advice would greatly appreciated..

 

[gmanpaint]

Check the Fuel pressure.

 

[MrShorty]

I'm going to put in a second vote for checking fuel pressure -- especially when the symptoms are present. The first time I replaced the fuel pump, the new, aftermarket pump had an intermittent problem with heat. When the pump overheated, it would behave similar to what you describe -- kind of cut in and out. Fuel pressure test should show if the pump is generating enough pressure.

 

[wouldsman]

TPS sensor ok.

So I changed out the TPS sensor this evening and in the same amount of distance from the house, got the same result. However, I did discover something just as strange. For the last week since this problem began, I've had to stop a couple of times coming home from town and let it cool down before I could continue forward, again, the temp gauge is reading normal and the rig is not over heating for sure. But tonight after I put the tps sensor on when it started doing it, I stopped, turned it off and then started it right back up & went for another couple of miles before it started doing it again, when it did, I didnt even stop, just put the clutch in turned the ignition off, then right back on, let the clutch out and made it the rest of the way home w/ out a problem!
Does that sound like it could be fuel pump problems? Could someone maybe point me in the right direction as to how to test the fuel pressure, thats something I've never done, but have a well equipped shop and should have the right tool to get it done, if not I'll buy it.
Again any help would be appreciated...

 

[Bwana Bob]

Wouldsman,

You will need a fuel pressure gauge, available at most auto parts stores or Sears.
The fuel pressure test port is on the fuel rail on top of the engine, near the fuel pressure regulator. The fitting is a Schraeder valve protected by a small plastic cap. The gauge will come with an adapter. I don't have my notes here, but as I recall, at idle the pressure is 30-35 psi and if you rev the engine it will go up to about 35-40 psi.

Wear safety glasses. If the fuel rail is pressurized, the test port will spritz a little fuel when you connect and disconnect the gauge. The gauge that I have has a pressure relief button and a drain hose to depressurize the fuel rail before disconnecting the gauge.

Bwana Bob

 

[MrShorty]

There's a "fuel pressure mini-diary" over in the Under the Hood forum that has pretty good instructions for a fuel pressure test.

 

[wouldsman]

Thanks guys, I'll check it out in the morning.