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5.3 LS Stall/Sputter in Certain Conditions (Outside Temp, Engine Warm, etc)...

PWagon

PWagon

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I have a very unique situation where my '86 K5 (with a 2003 GMC 5.3 LS engine) will suddenly begin "cutting out" like it's losing fuel pressure. Keep in mind that I only see this problem on days 80° degrees and warmer. I can go all winter long (months) without a single problem. On day one of 80° degree weather it cuts out after about 8 miles of driving. Once it starts, the engine slowly cuts-out for 1 to 2 seconds then barely fires on enough cylinders to stay running. It'll take maybe 4 to 6 seconds for the engine to die. Keep in mind that I only see this problem on days 80 degrees and warmer. So, here's what I've tried.

Replace fuel pump relay - I bought the $100+ all in one high pressure fuel pump wiring kit from Summit, properly installed it, and it still did not fix the stalling problem. I can still hear the fuel pump prime prior to starting the engine. I no longer believe it's fuel pump wiring related.

Fuse block relay replace - I've replace the relay that providing power to my PCM, pink wire accessores (fuel injectors, sensors, etc). I've looked at the wiring and none appears to be hot/melted. I'm not popping fuses either.

Rewire ignition fuse block - I really don't want to, but I guess late tonight I'll install a new fuse block I ordered off Amazon and install brand new wiring, terminals, and a new relay to power the PCM, injectors, sensors, etc.

Conditions noticed when engine cuts out:
  1. 80° (or hotter) temp outside
  2. Engine starts up again and runs fine after about 30 minutes or so (to cool down)
  3. Truck's been running about 8-10 miles
  4. I just noticed yesterday that the computer (PCM) was reset (my check engine light went off and stayed off until an hour later when it realized my knock sensor is bad). Now I'm wondering if the PCM is losing power or may be going out??
Does anyone else have any suggestions here? I'm at a loss.
 
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I just placed an order with Summit Racing for 2 new knock sensors and decided to take the "shot-gun" approach and added a new throttle position sensor and crankshaft position sensor to the order. I've read several articles where people claim the crank sensor may be faulty if it gets hot and quits sending signal to the PCM. After it cools it works again. This may be a shot in the dark, but I'll take my chances I guess. I also added a fuel pressure gauge and -4 AN to 1/8 female NPT adapter to fit it to my fuel rail Schader valve. Hopefully this weekend I can get it all installed. More to follow...
 
Have you done the crank position relearn procedure? I would do that before replacement and after.
 
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Babaganoosh said:
Have you done the crank position relearn procedure? I would like that before replacement and after.
Click to expand...
Good question. I honestly have no idea how to do the crankshaft variation relearn procedure. Guess I have something else to add to my to-do list.
 
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I have gotten lucky with just pulling ecm fuses and resetting computer each time something is replaced. Seems to work fine when I don't have the Snap On Solaris scanner available.
 
PWagon said:
I have a very unique situation where my '86 K5 (with a 2002 GMC 5.3 LS engine) will suddenly begin "cutting out" like it's losing fuel pressure. Keep in mind that I only see this problem on days 80° degrees and warmer. I can go all winter long (months) without a single problem. On day one of 80° degree weather it cuts out after about 8 miles of driving. Once it starts, the engine slowly cuts-out for 1 to 2 seconds then barely fires on enough cylinders to stay running. It'll take maybe 4 to 6 seconds for the engine to die. Keep in mind that I only see this problem on days 80 degrees and warmer. So, here's what I've tried.

Replace fuel pump relay - I bought the $100+ all in one high pressure fuel pump wiring kit from Summit, properly installed it, and it still did not fix the stalling problem. I can still hear the fuel pump prime prior to starting the engine. I no longer believe it's fuel pump wiring related.

Fuse block relay replace - I've replace the relay that providing power to my PCM, pink wire accessores (fuel injectors, sensors, etc). I've looked at the wiring and none appears to be hot/melted. I'm not popping fuses either.

Rewire ignition fuse block - I really don't want to, but I guess late tonight I'll install a new fuse block I ordered off Amazon and install brand new wiring, terminals, and a new relay to power the PCM, injectors, sensors, etc.

Conditions noticed when engine cuts out:
  1. 80° (or hotter) temp outside
  2. Engine starts up again and runs fine after about 30 minutes or so (to cool down)
  3. Truck's been running about 8-10 miles
  4. I just noticed yesterday that the computer (PCM) was reset (my check engine light went off and stayed off until an hour later when it realized my knock sensor is bad). Now I'm wondering if the PCM is losing power or may be going out??
Does anyone else have any suggestions here? I'm at a loss.
Click to expand...



Sounds like a fuel pressure issue.
Where is your fuel pump located? If it's not in the tank you need to move it to the tank.
 
I installed the Wallbro (Corvette style) inline pump next to the fuel tank (may 6 inches away). It's wrapped in heat resistant insulation to stay cool. I ordered a fuel pressure gauge from Summit, so I'll soon be able to monitor the fuel pressure.
 
I don't know what your emissions requirements are where you live but this sounds similar to a faulty EGR valve.
 
As long as I'm going to replace the knock sensors, I might as well replace the camshaft position sensor also. That's another $50 to Summit Racing. :doah:
On a side note, I've been reading a lot of articles where other folks are having my same damn problem. Most of those people are noticing ambient weather temps of 80° F, engine stalls out at random times, and will restart after the engine cools down. This is apparently a common issue with the Gen III LS engine. Some of those folks fixed their issue by replacing the crankshaft variable position sensor. Like I mentioned earlier, I'm taking the "shot gun" approach. I'll be replacing the following parts next week. It'll take a least a weeks worth of driving in warm weather before I can say it's fixed or not. Parts I'll be swapping out:

  • crankshaft variable position sensor
  • camshaft position sensor
  • throttle position sensor
  • both knock sensors
  • new ignition relay
  • installing fuel pressure gauge to fuel rail
 
Just remember, new doesn't mean good. Ever. Many times replacing parts doesn't fix anything because the parts you used are junk to begin with.
 
I considered that when I placed the order. That's why all parts I ordered were either AC Delco or Delphi brand.
 
I'm at a complete loss here. I've replaced the bad knock sensors (both), crankshaft position sensor, cam position sensor, and fuel filter, but I still have an issue with stalling and the engine will die after it restarts on a hot day. I finally got my fuel pressure gauge installed last night, so I'm hoping the next time the truck "acts up" I can verify the fuel pressure. My next suspicion would be vapor lock leading up to the fuel pump. Has anyone else seen a problem like this before? Like I mentioned, I can drive the truck and it runs GREAT until these three things happen :
  1. it's over 80 degrees outside
  2. the engine gets to running temp
  3. I intentionally kill and restart the engine
Then it spits, sputters, and dies. Then I have to wait about 20-30 minutes before it'll restart. Then it runs GREAT until I repeat the process. WTF?!?!?
 
Do you have a factory fuel pressure regulator installed on the fuel rail, or an aftermarket part?

If it's OEM, pull the vaccum hose off and look for fuel dripping out of the regulator nipple. Sometimes the diaphragm will fail and the engine will suck raw directly into the intake. Makes for hard hot starts and could potentially cause stalling because of the extremely rich mixture it causes.
 
Welp, I'm about to pull all my hair out as I cannot figure this problem out. I only have one trouble code (P0332) and it's for the knock sensors (both have already been replaced last week). Yet I still see the error code even after I clear the codes. I also still have a difficult restart after the engine is warm and the outside temp is over 80 degrees. It'll start, then sputter for 10-15 seconds like it's trying to die. Pressing the gas pedal does not help or hurt the situation. After I give it 30 minutes to cool down the truck will start and run like brand new. I've replaced the following:

  • crankshaft variable position sensor
  • camshaft position sensor
  • both knock sensors (fun as sh*t to get access to)
  • fuel pump (measured 52 psi at fuel rail)
  • fuel filter
  • moved the fuel pump as close to tank as possible (and lowered it)
  • added reflective heat shield to all fuel lines, pump, and filter
My next financial expense adventure will likely include the following:
  • replace throttle position sensor
  • replace mass air flow sensor
  • replace idle air control sensor
  • wash the truck and engine in holy water
I could sure use some suggestions here as I'm running out of patience and money. Suggestions??
 
You don't have any fuel lines running over the exhaust or converts do you? Could be vapor locking the fuel rail if it's a non return style fuel system.
 
Are you running the factory squarebody tank still? What did you do for the pickup tube and vent/return lines?
 
Had a similar issue with a 5.3 that turned out to be a fuel pressure regulator. You can borrow the fuel pressure test tool from your local auto parts store and check it without spending more money on parts.
 
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