'96 Stalling Out Under Load

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napir

napir

10 Year 15 Year
Joined
May 25, 2010
Threads
14
Messages
218
Location
Colorado Springs
Just started this morning, I was driving along and hit the throttle and the truck got super sluggish, throttle hesitated then finally I got some power. Came home, took some video of what's going on. In the first video towards the end, I have it WOT and there's no power and then you hear it suddenly kick in. In the second video, it's full WOT and no power. Also, hopefully you can hear it, but once the power drops off, the motor just lugs away like an old cam'd V8.

Truck starts fine, has been running like a top all winter. Was planning to change plugs, clean throttle body, and just a general tune up in a few weeks. I unplugged the TPS and it acts the same way regardless of the TPS being plugged in or not, which is an old trick my neighbor mentioned trying, but not exactly scientific.

No codes. Did some searching and I'm going to pull out and test the knock sensors. Anything else obvious I should look at before I start throwing parts at it?



 
How's your air cleaner? Water in your fuel? Plugged injectors, fuel filter, all your wires secure, spark plugs in good shape? Do you run additives in your fuel? Are all of your vacuum hoses in good shape?
 
Maleficio said:
The fact that disconnecting the TPS causes no changes to the problem tells me it is causing the problem.
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No codes caused by the TPS? That seems strange. Is the CEL illuminating at startup?
 
Newer cars have dual TPS. If the ECU detects disparity between the two inputs then it can alert you with a CEL. One TPS cannot allow the ECU to detect a failure. It simply has to trust the input and regulate fuel delivery accordingly.
 
danthman114 said:
How's your air cleaner? Water in your fuel? Plugged injectors, fuel filter, all your wires secure, spark plugs in good shape? Do you run additives in your fuel? Are all of your vacuum hoses in good shape?
Click to expand...

No additives, vacuum is good all around. Good things worth checking either way, will go through those, thanks.
 
Last edited:
blkprj80 said:
Since it revs up from idle, then drops out, I'd suspect fuel delivery.

Unfortunately, fuel pressure is hard to check.

Things to check:
Fuel Filter
Fuel Pressure Regulator
Fuel Pump Relay
Fuel Pump

You can test the TPS easily if you follow the FSM.
Click to expand...

I'm starting to think it might be a bad tank of gas. I've had zero symptoms (it's a DD) until today and I just filled up yesterday. I wonder if running an octane booster or water remover would be worth it? The suddenness of it, and my ability to repeat the behavior points me to gas, but I have no idea a good way to test that.
 
napir said:
I'm starting to think it might be a bad tank of gas. I've had zero symptoms (it's a DD) until today and I just filled up yesterday. I wonder if running an octane booster or water remover would be worth it? The suddenness of it, and my ability to repeat the behavior points me to gas, but I have no idea a good way to test that.
Click to expand...

You can always pull or loosen the plug on the fuel tank and drain off some of the bottoms of the fuel to check fuel quality. Water always settles to the bottom. Of course, use nitrile gloves and have a big enough container to hold whatever fuel you drain off. Don't use octane booster or water remover. If you purchased fuel with ethanol, the ethanol is the water remover. The retailer you purchased the fuel from could have bad fuel with water in it. Gasoline with 10% ethanol only takes .5% of water added to it to cause phase separation which ruins the fuel quality and condition.

Or just pull the fuel pump assembly through the access plate located under the second row seats. The fuel pump sock can be changed and a sample of the fuel could be obtained there as well.
 
Yes, I was thinking fuel filter or bad gas as well. Do what @SUMMIT CRUISERS suggested.

It's really easy to drain some fuel out of these. Let it sit in one place for a few hours, then drain off the bottom.
 
SUMMIT CRUISERS said:
You can always pull or loosen the plug on the fuel tank and drain off some of the bottoms of the fuel to check fuel quality. Water always settles to the bottom. Of course, use nitrile gloves and have a big enough container to hold whatever fuel you drain off. Don't use octane booster or water remover. If you purchased fuel with ethanol, the ethanol is the water remover. The retailer you purchased the fuel from could have bad fuel with water in it. Gasoline with 10% ethanol only takes .5% of water added to it to cause phase separation which ruins the fuel quality and condition.

Or just pull the fuel pump assembly through the access plate located under the second row seats. The fuel pump sock can be changed and a sample of the fuel could be obtained there as well.
Click to expand...

Good stuff, thanks. I think I'll pull the pump and replace the sock, test the fuel and go from there.
 
The fuel filter is under the intake manifold. A giant PITA. May have to think about changing that too.
 
Maleficio said:
Ever seen anyone relocate the fuel filter?
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Yes there are a number of folks that have. Do a search for fuel filter relocation in the 80 section and you should find it.
 
So while waiting for parts, I threw a bottle of Iso-Heet into the tank just to rule that out. Fired her up, let her warm up and drove around for about a half hour and no more stalling out, so I'm chalking this one up to bad gas. Either way, I'm replacing the fuel filter and a few other things just to make sure. Thanks again for all the suggestions.
 
Remove driver front wheel and get in the wheel well. You can get 2 hands in there to do PHH, fuel filter , starter.
 
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