Truck stalls when hot

[EDGECRUSHER]

Installed VSS today and got the speedo back
thanks for all the help.
Unfortunately I still have an erratic idle.

 

[twomanymontes]

One problem down, one to go! LOL!

Still no luck on a vacuum leak I take it

 

[EDGECRUSHER]

Gonna get a few feet of new line and replace it all next. Just kinda worn out after the holiday weekend

 

[EDGECRUSHER]

replaced some questionable vacuum lines but still no improvement. In fact, after stalling the engine while checking vacuum leaks and pulling that large hose on the front which runs to the PCV, the engine would not start and threw the code 15 again. I had to disconect the battery for quite a while inorder to clear that code and when I tried starting again, it wouldn't until I shot a little starting fluid into the TB.

That makes me question my fuel pressure again. I have a pressure guage I installed inline inside the cab back when I redid the fuel lines. It reads 11.5 psi when the engine is running but it's a small rather cheap gauge and I'm questioning whether there are fluctuations going on that I'm not seeing.

I'm curious what the minimum psi is required to keep the TBI system working. I've heard of FI systems refusing to work because they dropped one psi, however I was under the impression our TBI was a little more lenient? I do know that 13psi is optimum and there are regulator kits to make this so.

I'm just thinking that the leak at the tank which I wasn't thinking was an issue because I can read 11.5 psi at the guage is really causing more of a starvation issue than I wanted to admit.

Any thoughts?

 

[EDGECRUSHER]

I still have a change in idle whenever the hood is moved. Pull the hood latch - rpm jumps up a bit. Slam the hood down- rpm jump again. Can't figure that one out but I think it's a clue to my problem somehow. Pulling the hood latch is such a small movement in the grand scheme of things, I just don't see how that's gonna influence rpm and a pot hole in the road doesn't... but it's happening nonetheless.

 

[magimerlin]

If just moving the hood changes thing... There is a bad connection somewhere that is getting disturbed by the force of shutting or moving the hood. Have you checked all your grounds to make sure that they are all clean and secure(batt to fender, batt to intake, head or intake to firewall, and firewall to frame). In an electrical issue that should always be checked first in my book... Check all your connections/plugs under the hood.

The snap-on MT-3500 a.k.a. the "Brick" is an invaluable tool. Looks like you have thrown a few parts at the truck. Check eBay for the MT2500, I picked mine up there for I think it was 200 and it included a bunch of stuff that I use regularly on mine and others vehicles..

As mentioned before the coolant temp sensor for the temp gauge on the dash and is located on the side of the motor. The coolant temp sensor for the pcm is in the intake. The one for the gauge has one wire and the one for the pcm uses two. Look into the top of the actual sensor to see what one actually got the first time and adjust accordingly if need be.

 

[magimerlin]

I would also have your icm(ignition control module) checked even though it was already replaced. When they test it have them do it a few times, like 6+, so that is heats up nicely. They will be able to tell when that happens...lol When they are testing it make sure that they are lightly tapping on it. When you put it on in the first place, did you put the goop on the bottom of the sensor that should have come with it? If not that can kill it as it is a heat transfer type goop. Heat can kill a icm real fast like. If it still tests good after testing hot you will need to put that goop back on the sensor before you reinstall it. I think Auto Zone sells it on there little .99 cent hanger rack things if I remember right.

 

[EDGECRUSHER]

Well thanks for the ideas. I've visited most of them already. Got a friend with a brick, hopefully I can get him to loan it to me. As far as the hood and grounds-you'd think it would be something like that yet how is it I can run the truck down a washboard dirt road without a symptom? At one point I even suspected maybe the light on the hood was shorting out and somehow dragging down the electrical system.

Last night I changed the tranny fluid and replaced a beatup looking O2 sensor. Still no improvement.
1. Still haven't picked up the coolant sensor for the gauge but the ecm sender should be working fine.
2. ICM was tested and proved fine and also replaced and proven fine.
3. All vacuum lines have been tested.
4. Fuel pressure seems OK despite the fact that sometimes after the engine has been run long enough and shut down, a couple squirts of starting fluid are needed to get it to fire again. There has been a small gas drip/leak at the tank for the last year.
5. Distributor has been rebuilt w/ new cap/rotor/wires/plugs. Confirmed spark
6. Coolant level checked
7. Battery replaced
8. Grounds intact
9. im sure im missing something

symptoms at this point;
1. engine starts fine cold.
2. if hood is shut or latch mech pulled engine rpm changes slightly.
3. once warmed up idling- engine starts to fluctuate rpm randomly
4. neutral idling, engine tends to run about 500 rpms higher than normal
5. when put into drive brakes on, engine can stumble momentary if not stall. Idle still high, transmission is pushing against brakes rather firmly.
6. when accelerating, off idle the engine will stumble/cut-out, extra throttle seems to keep it from stalling. Then engine accelerates from there which seems a little low on power.
7. Cruising at 55mph, while the engine misses subtly the transmission is trying to find/stay-in overdrive but never really seems to get there. Engine Rpms higher than normal.
8. deceleration, engine seems to shift fine until reaching shift between second and first where it can possibly stall/stumble.
9. whenever there is a stumbling/stalling event shifting into neutral usually helps, raising the rpms and taking the drag off the motor thereby smoothing out

I'm really starting to think maybe this is something to do with the 700R4 transmission but all the symptoms don't necessarily;iy point that way. Why is starting fluid needed to restart after hot shutdown? Leaning toward a heat related fuel problem...

typing this all out really helps keep my thinking process straight.

 

[EDGECRUSHER]

Experience is telling me this is a vacuum related problem though. Maybe I'll get crazy with a can of carb cleaner again tonite.

 

[EDGECRUSHER]

Now it is stalling when I get out and shut the door just like the door is the off switch. I think I'm gonna have to get up close and personal with the wire harness. I'm so ready for a new truck lol