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desperately need help!

I had this issue when I first built the Jimmy. Everything was new, except the wiring harness. Try holding the throttle open a little and start moving wires at theback of the block then start working forward. Was an intermitant issue. Turned out to be the harness to the TPS. Under load, the harness moved enough to kill it.
 
ktmoutfront said:
I had this issue when I first built the Jimmy. Everything was new, except the wiring harness. Try holding the throttle open a little and start moving wires at theback of the block then start working forward. Was an intermitant issue. Turned out to be the harness to the TPS. Under load, the harness moved enough to kill it.
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I second this. I had some wires that were the factory twisted pair stuff, and were cracked inside the twists. They were shorting under the right conditions, but looked fine until i untwisted them in good light.
 
Thanks guys I'll give that a shot tomorrow and let you know what I find.
 
Might want to take a fuel sample and see if any water is in it too...sometimes an engine will run great with no load with quite a bit of water in the gas,especially with todays alcohol laced gas--but it will fall flat on its face when its put under a good load..

A friend had a later model GM pickup doing something similar,it acted like it had a fuel starvation problem after you floored it for about 10 seconds..it would take off like a scalded ape,then bog out and stall,sometimes with a stumble and a pop back in the air filter...

He went to replace the fuel pump and when he dropped the tank and removed the sending unit,the tank had a good gallon of water on the bottom,along with mud,leaves,and other crap...he discovered the fuel filler neck had rusted thru and the tire was spraying rain water into the neck!...it ran like a bear after he drained the tank and put it back in without changing the pump,and he cut out the rusted section of the filler neck and spliced it with rubber hose rated for that use...he also replaced the little fuel line joining the pump to the sending unit--it was all swollen and soft,probably due to ethanol--that may have contributed to the problem too..

I have seen another vehicle act that way when the gas cap didn't vent right and allow air into the tank,it would accelerate fine up to about 45 mph,then fall flat and stall,and would re-start instantly and do it again...if you feathered the gas pedal it would run normal all day...

The customer admitted to "losing" her gas cap one day after forgetting to put it back on after filling the tank,and when she returned to ask if anyone found a gas cap,the station manager showed her a cardboard box FULL of gas caps,and said "any of these look like yours"?...she picked one and it fit,but may have not been correct or working right...a new one from a parts store corrected the stalling issue..a lot of garages tried "fixing" that car and threw many dollars worth of parts at it,with no results too..

My friend has seen a few charcoal canisters fill with gasoline and "flood" the engine under heavy acceleration on a few vehicles too--this usually resulted from people filling the gas tank right up to the CAP ,which lets gas flow back into the evaporative emissions recovery system..you should stop filling the tank the first time the pump nozzle clicks off...
 
The K5 I just bought has a similar issue and my friend believes it is a plugged cat. I haven't had the time to check it yet though.
 
kennyw said:
The K5 I just bought has a similar issue and my friend believes it is a plugged cat. I haven't had the time to check it yet though.
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Doubt it would run as well as it does with a plugged cat.
 
It is possible if it is not completely plugged. Either way I will watch this thread because I'm not sure what the issue is either.
 
I have seem them run like this and it was a worn out dist. Idle and low speed it was bad but at higher rpm it was fine. Just something to check. If you can move the rotor back and forth.
 
87vandal said:
I can't figure out what's going on with my k5. Its a 87 TBI 700r4 . the truck runs great. It will even spin the 35s without even thinking about it, but put her in drive and hit the road and it dies! Starts right back up try and drive and dies! I've replaced a lot of parts and have no idea why to do next! New parts... Fuel tank ,pump ,lines, coil, egr, IAC , cap, rotor, plugs,wires, ignition control module, neutral safety, and ecm... Please help!!! Oh no codes either!
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From a GM tech manual.

There are circumstances that could occur with a failing throttle position sensor that may not set a trouble code. One of the most common symptoms of a failing TPS would be a tip-in hesitation or stumble when you apply throttle to take off from a stop. This can be caused by a dead spot in the TP sensor’s internal circuitry, which usually causes the output voltage signal to not change (or it drops out) when the throttle opens. Unfortunately this type of failure is not easy to diagnose without the proper tool – a digital waveform scope. Most digital volt meters and scan tool displays will not respond fast enough to show this type of a glitch; but some may. If you do find this fault, then the obvious fix is to replace the TP sensor.
 
Maybe something loose with the ignition switch, when driving it gets jarred and cuts out? Start it up and start moving wires around to see if you can reproduce the problem sitting still. I would also think about rigging up a test light on the coil wire so you can see if it goes out when it dies while driving. Also if there's a way to connect up your fuel pressure gauge so you can drive and see it.

I had a Mitsubishi and it would cut out and die, the filter sock in the tank was plugged up. The only way I found it was driving around with my fuel pressure gauge where I could see it. When it cut out I could see the pressure drop.
 
OK need update.. Moved every wire on the truck can't get it to do it sitting still. Tried a new tps. Again still nothing. Cats are not clogged ( there are none) I'm losing my mind here!!!
 
OK here we go I pulled the neutral safety switch off and if I manually move the switch to the drive position the truck starts to stumble then dies out??
 
This may be a stupid question or previously asked, but with all the parts you changed, was the fuel filter one of those parts and if so is it possible you put it on backwards?
 
Nothing is stupid at this point... Yes its new and installed properly
 
Have you tried a bottle of Heet (removes water)? Or a bottle of Sea Foam (cleans carbon build up)
 
No I haven't tried heet or seafoam . and no different if any thing seems worse
 
87vandal said:
No I haven't tried heet or seafoam . and no different if any thing seems worse
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When it dies, does it die like you just cut the key off or does it slowly die like starving for fuel? does it easily start back up? If it were mine, I would consider maybe jumpering the fuel pump relay and driving it to see if it still had the problem. Is there any way you can hookup your fuel pressure gauge where you can drive it and see it?
 
It acts like its either starving or flooding. And it starts right back up no issue what so ever..I've tried jumping the pump it made no difference. And I'm not sure I'll try setting up the gauge when I drive it.
 
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