Stalling while driving.

[Skunkape]

05 tahoe 4wd 5.3 284k miles.
While driving 65mph state highway the engine stalled out. Just seemed to quit, no stutters, backfires or choking. Pulled it over with no power and turned the key off. After waiting a few minutes, it started right up with no issues.
After driving another mile or 2, it did it again. In the same way, I started it again drove a couple miles more. This happened 5 times in a 16 mile stretch until I reached a gas station. At this point it had just under a half tank of gas, so I thought I would fill it up just to make sure the fuel guage hadn't malfunctioned.
It took 14.4 gallons of gas to the neck, started right up and drove the remaining 24 miles home, on county roads, with no issues.
No check engine lights and the only code it's throwing is PO455. Any thoughts?
Fuel pump? Pressure regulator? Cam position sensor?
Thanks for your time.

 

[strutaeng]

That's an EVAP code, which doesn't typically cause driveability issues.

Could be fuel delivery issues, yes.

To diagnose you need a fuel pressure gauge with a long hose. Tape the gauge to the windshield and see if your pressure drops right before it stalls, then go from there.

 

[justirv]

05 tahoe 4wd 5.3 284k miles.
While driving 65mph state highway the engine stalled out. Just seemed to quit, no stutters, backfires or choking. Pulled it over with no power and turned the key off. After waiting a few minutes, it started right up with no issues.
After driving another mile or 2, it did it again. In the same way, I started it again drove a couple miles more. This happened 5 times in a 16 mile stretch until I reached a gas station. At this point it had just under a half tank of gas, so I thought I would fill it up just to make sure the fuel guage hadn't malfunctioned.
It took 14.4 gallons of gas to the neck, started right up and drove the remaining 24 miles home, on county roads, with no issues.
No check engine lights and the only code it's throwing is PO455. Any thoughts?
Fuel pump? Pressure regulator? Cam position sensor?
Thanks for your time.

My first thought was fuel pump, I'd follow Strut's advice to monitor fuel pressure in real-time.

 

[OR VietVet]

Sounds like a fuel issue except that you said it did not stutter at all, you said it just died. Definitely check fuel pressure with long hose and gauge on drive.

Plus, do not, I repeat, do not fill fuel up to the neck. Remove nozzle when the pump clicks off. You have now damaged the eval system and have fuel in the charcoal cannister.

I would bet, if a new fuel pump fixes the problem, you will still set codes for evap system problems.

 

[Skunkape]

Sounds like a fuel issue except that you said it did not stutter at all, you said it just died. Definitely check fuel pressure with long hose and gauge on drive.

Plus, do not, I repeat, do not fill fuel up to the neck. Remove nozzle when the pump clicks off. You have now damaged the eval system and have fuel in the charcoal cannister.

I would bet, if a new fuel pump fixes the problem, you will still set codes for evap system problems.

Thanks Strut. I didn't know that, but it makes sense. Won't be doing that anymore.

 

[Skunkape]

Thanks Strut. I didn't know that, but it makes sense. Won't be doing that anymore.

that reply was for Or VietVet

 

[viven44]

New fuel filter while at it

 

[Skunkape]

Update;
Test 1- fuel pressure:
With new Guage hooked up, key on, it reads 54 psi, but then it slowly (30-60secs) drops down to 38 and lower. Chilton says it should be between 55 & 62. The tps made a loud click before the pressure started to drop.
Started the engine and the fuel pressure jumped to 55 and held at idle but the needle vibrated the whole time. It was just the engine running I'm sure.
Chilton says if the pressure is low, it's indicative of clogged fuel lines, fuel filter or a faulty pressure regulator, both of which are part of the fuel pump assembly, in the FULL gas tank. I was guessing the regulator or filter when it was stalling out, especially since it started right up again.
Just for grins I'll test the tps. That's what a buddy says it is.

 

[strutaeng]

Update;
Test 1- fuel pressure:
With new Guage hooked up, key on, it reads 54 psi, but then it slowly (30-60secs) drops down to 38 and lower. Chilton says it should be between 55 & 62. The tps made a loud click before the pressure started to drop.
Started the engine and the fuel pressure jumped to 55 and held at idle but the needle vibrated the whole time. It was just the engine running I'm sure.
Chilton says if the pressure is low, it's indicative of clogged fuel lines, fuel filter or a faulty pressure regulator, both of which are part of the fuel pump assembly, in the FULL gas tank. I was guessing the regulator or filter when it was stalling out, especially since it started right up again.
Just for grins I'll test the tps. That's what a buddy says it is.

Do you have a way to monitor the fuel trims while truck is running? I'd be expecting to see fuel trims moving towards the lean side as the fuel pressure drops.

Also, what happens to the fuel pressure at say, 2k, 3k and 4k RPM? And the fuel trims? Are they within 1-2% of each other between bank 1 and Bank 2?


You could also monitor the throttle % on your scanner since you seem to suspect TPS. This is a drive by wife throttle body, right?

Edit: you can siphon some of the gasoline from your tank so you are not dealing with a full tank weight.

 

[Skunkape]

Do you have a way to monitor the fuel trims while truck is running? I'd be expecting to see fuel trims moving towards the lean side as the fuel pressure drops.

Also, what happens to the fuel pressure at say, 2k, 3k and 4k RPM? And the fuel trims? Are they within 1-2% of each other between bank 1 and Bank 2?


You could also monitor the throttle % on your scanner since you seem to suspect TPS. This is a drive by wife throttle body, right?

Edit: you can siphon some of the gasoline from your tank so you are not dealing with a full tank weight.

Thanks Strut.
Yea it's a dbw t body, so no real way to test it. I can add that idling or throttle response hasn't been a noticeable issue, as a symptom. No codes either.
I have a decent scanner but it's too smart for me so far. I'm not sure it (or I) could measure fuel trims. I know it does real- time scans, so maybe I'll hook it up take it for a quick drive? I'll for sure hook up the fuel pressure tester and run it at higher rpms. The fuel pressure is obviously an issue which makes me lean toward the fuel pump assembly.
But I was thinking the cam position sensor for a couple reasons; 1 I've been running with a failed oil pressure sensor for months. Now it's leaking I noticed from underneath, and it's caked oil all over the cps. I've heard of them failing over that. 2 the stalling out while driving with no warning is typical of a failing cps, as I've seen on utube.
Anywho, I'll run a real-time scan and revved up fuel pressure test tomorrow and go from there. I'll keep you posted.

 

[rockola1971]

Update;
Test 1- fuel pressure:
With new Guage hooked up, key on, it reads 54 psi, but then it slowly (30-60secs) drops down to 38 and lower. Chilton says it should be between 55 & 62. The tps made a loud click before the pressure started to drop.
Started the engine and the fuel pressure jumped to 55 and held at idle but the needle vibrated the whole time. It was just the engine running I'm sure.
Chilton says if the pressure is low, it's indicative of clogged fuel lines, fuel filter or a faulty pressure regulator, both of which are part of the fuel pump assembly, in the FULL gas tank. I was guessing the regulator or filter when it was stalling out, especially since it started right up again.
Just for grins I'll test the tps. That's what a buddy says it is.

That TPS isnt causing you to have low fuel pressure. Your faulty fuel pump is. "38psi and lower" as you stated aint gonna cut it for a 5.3/6.0....Unless you have a fuel filter on the frame rail drivers side then it could be that. It takes an ungodly amount of debris to plug up the sock at the fuel pump. The old sugar in the tank method sure will do it but natural debris acquired by gas stations likely are never the cause.

 

[Skunkape]

Update 2;
I have been driving all over creation and it has not repeated the stalling issue. The guage has been everywhere, but I haven't let it get below an 1/8 of a tank. Go figure. I'm leaning towards the fuel pump though, because since I've been paying attention to it, it seems it's not as powerful or zippy as usual. Fuel mileage seems to be off also.
I did run some real-time scans and the tps and pedal are communicating with no issues. The left and right bank fuel trims appear to be within desired values, however on the low side (if I'm reading it right) through low rpm ranges on a typical drive.

Thanks for input and I will keep you posted.

 

[viven44]

If you have a frame mount fuel filter, if it’s clogged it could affect pressure… the clog may be intermittent depending on the particulates and where they are … when you turn off the vehicle any backflow can temporarily unclog .. similar to any filter in oil pickup tubes in engine/trans

 

[Skunkape]

Update 3;
The stalling issue has still never repeated, but I blew out a brake line. Since the gas tank had to be dropped to make the repair, I figured I would go ahead and replace the fuel pump while it was down. This entire project was a horror story from beginning to end, and now that it's running and stopping great, the $%#@& fuel guage is reading less than 1/2 tank after a fill-up.

 

[OR VietVet]

Update 3;
The stalling issue has still never repeated, but I blew out a brake line. Since the gas tank had to be dropped to make the repair, I figured I would go ahead and replace the fuel pump while it was down. This entire project was a horror story from beginning to end, and now that it's running and stopping great, the $%#@& fuel guage is reading less than 1/2 tank after a fill-up.

Did you replace with a complete AC Delco unit or genuine GM unit or did you do, just the pump, and no sending unit?

 

[Jobi-Wan Kenobi]

If you do still have random shutdowns the crank position sensor can cause that and not trigger fault codes.

 

[Skunkape]

Did you replace with a complete AC Delco unit or genuine GM unit or did you do, just the pump, and no sending unit?

Replaced with a complete Delphi unit. I was getting worried that I boogered the float assembly upon install, but I remembered that the guage has stuck before. Haven't had a problem recently, before the new pump, but the guage cluster is messed up; typical for GM. That's where I'm hanging my hat for now. Not sure when or if I'll ever get the cluster fixed, but I sure don't want to drop the tank again.

 

[Skunkape]

If you do still have random shutdowns the crank position sensor can cause that and not trigger fault codes.

Yeah I read that somewhere, but I was thinking it was Camshaft position sensor. Either way, it hasn't done that again.

 

[OR VietVet]

Replaced with a complete Delphi unit. I was getting worried that I boogered the float assembly upon install, but I remembered that the guage has stuck before. Haven't had a problem recently, before the new pump, but the guage cluster is messed up; typical for GM. That's where I'm hanging my hat for now. Not sure when or if I'll ever get the cluster fixed, but I sure don't want to drop the tank again.

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