Truck stalls when hot

[EDGECRUSHER]

1992 Chevy K1500 5.7TBI pickup 210,000 miles
Problem when adequately hot, engine will stall out without warning repeatedly. (EDIT)- just started this spring
other symptoms:
surging at idle
engine code 15 coolant sensor thrown.
coolant sensor quit functioning approx 1 year ago. replaced with one from Advance, new sensor would take a long time to show engine warming up and would top out about half as high as old sensor when it was working. Shortly after replacement, heads showed signs of a coolant leak (drip after shut-down) which eventually disappeared and quit leaking. Coincidentally, the leak also occurred after Sea-foam had been run through the engine.
Fuel pressure gauge I installed on my dash always reads a steady 12psi while running. At start-up, if the ignition isn't turned to start in a certain length of time I then notice the pump is shutting off and it doesn't repressurize until the key is turned to ignition. I think this is normal.

Stalling only happens when truck is plenty warmed up. It runs like a top until then. Then once it stalls it can be really hard to get it to stay running again unless you let it cool down for a while.

parts replaced since stalling began:
Battery
plugs/wires
cap/rotor
pickup coil
ignition coil
electronic ignition control module

Parts still suspect:
coolant sensor
thermostat
electronic spark controller
AIC
ECM

notes:
I'm concerned about why the new coolant sensor doesn't seem to want to move the gauge needle. Also curious about how the radiator hose coming off the top of the engine runs up above the radiator which could cause a air pocket in the system. Never was a problem all these years so I'm thinking possibly a long shot.
I don't have access to a brick to watch what's going on and I'm extremely un-trusting of mechanics at dealerships (present company excepted of course) but I know I can get this figured out with some help. I believe this is a common problem just wondering what some of your experiences are. I've got most of the basic parts switched out already. I'm hoping I just got a bunk coolant sensor which replacing again will be my next step.

I've done a lot of searching on the web for causes. Any ideas about my particular situation would be appreciated!

 

[1997chevydriver]

Ok so you know its a temp related issue.

When it stalls have you checked for spark? Have you checked for fuel?

Also when you say you changed coolant sensor did you replace the one in the cylinder head only or did you replace the one in the intake manifold by the tstat housing too?

The one in the cyl head is ONLY for the gauge on the dash. The one in the intake mani is for the computer.

 

[1997chevydriver]

Just read the code 15 part. Replace the coolant sensor in the intake mani before you do anything else

 

[EDGECRUSHER]

Well honestly I only replaced the sensor on the intake which didn't fix the gauge issues I was having before. I was wondering if there was a second and would this be the one on the drivers side head above the exhaust? Is that basically the same sensor? Because I only see one listed at the part store.
Anyway, I fiddled a bit tonight. Topped off coolant, pulled intake sensor and checked for operation problem persisted. Finally I just cleared the codes and ran it for awhile then hopped in and took it down the road. It didn't stall yet it still seems a little slow to accellerate. Plus I got a new code! 15 didnt come back, now I have 24 which is vehicle speed sensor. I'm still trying to find out where this is. Also my manual says to check the TPS for function with this code which I'm about to do now.
I have to correct myself about the fuel pressure. It's actually running at 11.5psi and I have a slow leak at the lines at the tanjk which may account for the loss of pressure after initial key on/pump cycling. But that's without the engine running.

the plot thickens

P.S. It's weird but worth mentioning, when I slam the hood shut the idle goes up momentarily. I tried banging on the frame to mimick the bang of the hood and I can't get it to replicate only with shutting the hood. When I set the hood down lightly then push it the rest of the way down it also does not change the idle.

 

[EDGECRUSHER]

Just checked TPS and I get 5v signal when the throttle is closed. gonna try a new one...

 

[EDGECRUSHER]

replaced TPS and checked voltage and now it's within parameters. Took for drive and engine doesn't stall but now the speedometer isn't working. Never noticed that before. Needle just sits at the bottom but did jump once. Thinking now the VSS need replacement? Can anyone tell me where I can find this? I'm thinking it's on the tranny somewhere...

Also seems to be idling a little high, 1200-1300rpms. My thoughts are since I adjusted timing while it was running bad maybe I just need to take it back a bit now that it seems to be better.

any thoughts or words of encouragement?

 

[EDGECRUSHER]

BTW it didn't throw code 24 Vehicle Speed Sensor again...

 

[EDGECRUSHER]

Can I drive it like this or is it bad for the TC? Seems to shift harder...

 

[twomanymontes]

Without the Speed sensor reading the trans will shift erratic and harder than normal. Not the best for the transmission.

Not sure which transmission you have. There is a speed sensor is located in the transfercase just in front of where the driveshaft is. points to the driver's side. Check and make sure the wires haven't rotted going into the sensor, or the harness come loose and got caught in the driveshaft. Also look at both the input and output speed sensors on the side of the transmission.

Hopefully this helps

 

[EDGECRUSHER]

yeah hopefully my bread crumb trail will end soon.

thanks for the tips.

I have 700R4 btw
Napa was telling me there's a speed sensor on the rear end which costs $190 and is special order. First time I've heard of this but hopefully I'm not gonna have to worry about that. Seems now this topic is turning into a transmission thread lol