95 K2500 stumbles/sometimes dies under load

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Brandon_Lutz

Newbie
Joined
Oct 5, 2015
Messages
48
Reaction score
64
Location
Forest Hill, Louisiana
My 95 K2500 has just recently started stumbling under the load and exhibiting a hard start at times.

I noticed the issue popped up after I replaced the EGR valve with a new Delphi unit. I had started to get a CEL after about halfway to and from work every day. I put my code reader on it and saw that was code 32 for the EGR. So I got a new EGR valve and solenoid and changed them both out. Cleared the CEL code out and about a week later my truck began to stumble under load and actually die out a few times. Before the EGR replacement my truck had some hesitation at highways speeds if I went to pass someone or go up a hill some, but it never stumbled or died.

I temporarily capped off the vac line from the valve to the solenoid and the hard start issue went away, however the truck is still stumbling if I get on the pedal and put the truck under load.

It looks like I have good fuel pressure as I have a gauge on my TBI that shows it is a little over 12 psi. If I maniupulate the throttle by hand, the pressure remains unchanged on the gauge. For peace of mind I rebuilt the TBI recently because it still had the factory build kit in it. I also installed a new TPS when I rebuilt the TBI.

Plugs are looking good and I have spark on all the the cylinders. The distributor, ICM, Cap, rotor, wires, coil and plugs were all replaced about a year ago so I'm figuring those are not the issue. Plus I don't see any carbon tracing on any of those parts.

I'm leaning to something maybe wrong with the new EGR valve. Is there any specific test I can run on it to see if it is faulty? As I mentioned, if I plug the line between it and solenoid, my hard start issue goes away but it still stumbles under load. I also checked for vacuum leaks but I have not found any. Also, If I have the truck in park and rev the motor, it does not stumble or die out.
 

PlayingWithTBI

2022 Truck of the Year
Supporting Member
Joined
Jan 3, 2019
Messages
9,552
Reaction score
14,679
Location
Tonopah, AZ
The distributor, ICM, Cap, rotor, wires, coil and plugs were all replaced about a year ago so I'm figuring those are not the issue.
What brand/quality parts did you use? Just because they're newish doesn't mean they're still good. I had an ICM and coil go out in ~2000 miles.

Got a scanner? Look to see what's going on when it acts up.

Edit: did you set your base timing with the EST bypass wire disconnected?
 

Brandon_Lutz

Newbie
Joined
Oct 5, 2015
Messages
48
Reaction score
64
Location
Forest Hill, Louisiana
What brand/quality parts did you use? Just because they're newish doesn't mean they're still good. I had an ICM and coil go out in ~2000 miles.

Got a scanner? Look to see what's going on when it acts up.

Edit: did you set your base timing with the EST bypass wire disconnected?
Everything was with Delco/Delphi Parts. And the bypass wire was disconnected when the timing was set last year.

I don't have a scanner that can show me live data/do data logging. All I have is a scanner that flashes the lights for the OBD1 diagnostic codes. I no longer have the code 32 and it has not picked up on any new codes either.
 

1997

I'm Awesome
Joined
Aug 2, 2013
Messages
1,139
Reaction score
2,121
Location
B.C. CDN
How old is your 02 sensor?

my 95 had stumbling, running issues, no codes, and I have a scanner, no magic bullet, fired the parts cannon, a new ac delco 02 sensor and all is well.

i had never changed it and help from members here helped with the shot :)
 

Brandon_Lutz

Newbie
Joined
Oct 5, 2015
Messages
48
Reaction score
64
Location
Forest Hill, Louisiana
How old is your 02 sensor?

my 95 had stumbling, running issues, no codes, and I have a scanner, no magic bullet, fired the parts cannon, a new ac delco 02 sensor and all is well.

i had never changed it and help from members here helped with the shot :)
Changed the O2 sensor last night thinking it could have been the culprit.

Fuel filter was changed 3 weeks ago as well.

When it dies, I can smell gas, like it is super rich.
 

Brandon_Lutz

Newbie
Joined
Oct 5, 2015
Messages
48
Reaction score
64
Location
Forest Hill, Louisiana
Well, I eliminated a possible bad fuel pump this morning. I had a new one that I had purchased a few weeks ago for a tune up project and decide to swap it out this morning. Well pressures are about the same (13.5psi at the regulator) Old pumps screen looked pretty clear and I replaced the fuel filter 3 weeks ago. So it looks like my tank is pretty clean. Looks like it is possibly ignition related. Guess I'll swap out the coil tonight and go from there.
 

Brandon_Lutz

Newbie
Joined
Oct 5, 2015
Messages
48
Reaction score
64
Location
Forest Hill, Louisiana
does it get up to temp ok?
Yep, comes up to temp with no issue. So I definitely have it down to ignition related. Changed the coil this afternoon with a new one. The stumble is still there but not as noticeable as it has been. You really have to floor it now from a standstill to make it die. Before, just putting your foot into it with a moderate load would cause it choke down and die.

I'm going to replace the cap, rotor and ICM tomorrow once I get back home from work. It's still 98 outside right now and I've sweated enough for today lol.
 

Schurkey

Supporting Member
Supporting Member
Joined
Jan 14, 2018
Messages
10,970
Reaction score
13,759
Location
The Seasonally Frozen Wastelands
When my '88 K1500 had misfire at highway speed, it deteriorated over time. Eventually I had misfire at in-town speed, then stalling. Finally it stalled and would not restart. Of course this happened ~250 miles from home and tool-box.

GM dealership replaced the distributor mainshaft; showing me the old shaft-and-magnet assembly. The magnet was cracked in multiple places.

The magnets tend to crack through one or more of the four rivets that hold the assembly together. Note crack just under the "copyright" symbol, extending through the rivet and to the outer edge of the magnet.

You must be registered for see images attach
 

Brandon_Lutz

Newbie
Joined
Oct 5, 2015
Messages
48
Reaction score
64
Location
Forest Hill, Louisiana
When my '88 K1500 had misfire at highway speed, it deteriorated over time. Eventually I had misfire at in-town speed, then stalling. Finally it stalled and would not restart. Of course this happened ~250 miles from home and tool-box.

GM dealership replaced the distributor mainshaft; showing me the old shaft-and-magnet assembly. The magnet was cracked in multiple places.

The magnets tend to crack through one or more of the four rivets that hold the assembly together. Note crack just under the "copyright" symbol, extending through the rivet and to the outer edge of the magnet.

You must be registered for see images attach
I'll take a look at that tomorrow. Thanks!
 
Top