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Username Post: 1991 GMC STALLS WHEN SLOWING DOWN        (Topic#295021)
PaPa T 
Forum Newbie
Posts: 3

Reg: 03-19-13
03-19-13 10:12 AM - Post#2327705    

i HAVE A 1991 GMC 5.0, I'VE CHANGED ABOUT EVRYTHING BUT THE EGR VALVE. IT STARTS AND IDLES FINE AND RUNS DOWN THE ROAD WELL BUT WHEN I SLOW DOWN IT STARTS TO LOPE, LIKE ITS NOT GETTING ENOUGH GAS, AND USUALLY DIES. I'M ABOUT TO GO CRAZY, PLEASE HELP

 
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Pacgas 
Forum Newbie
Posts: 4

Age: 65
Loc: Minden, nevada
Reg: 03-18-13
03-19-13 03:34 PM - Post#2327798    
    In response to PaPa T

I just had a very similar a problem with my 88 k1500 with a 5.7. 350 automatic .
My truck would run fine until I slowed down, such as at an intersection where I would come to a stop, the truck would feel like it is going to die and I could not step on the throttle to keep it idling it would very quickly kind of surge then die. By surging I mean from normal idle rpm to dead stop, so it was trying to stay running but to me it felt like it was loading up.
I replaced the (iac) idle air control valve and all is well, in fact it never idled so smooth. If you end up replacing the iac, please note the instructions. Mine stated I was to drive it at speed of 40 mph for the computer to learn the iac values. I did not drive it at that speed as I live close to work but it did acquire the values without problems anyway.
Jim



 
Timothys Chevy 
Valued Contributor
Posts: 3863
Timothys Chevy
Loc: Fredericton, New Brunswic...
Reg: 09-24-03
03-19-13 07:48 PM - Post#2327868    
    In response to Pacgas

You might have a sticking torque converter clutch? That condition makes it feel like driving a stick shift, but not depressing the clutch when you stop, and it stalls the engine.

Its really common on the old 3 speed FWD transaxles.
~~Timothy~~

1984 Chevy Citation 2.5
2009 Pontiac Vibe AWD
1993 Buick Park Avenue
2001 Pontiac Sunfire GTX


 
PaPa T 
Forum Newbie
Posts: 3

Reg: 03-19-13
03-20-13 08:31 AM - Post#2327986    
    In response to Pacgas

I changed everything but the EGR valve, I didn't get any instructions I'll driving it to the store and back to see if it helps. thanks

 
Adam144 
Forum Newbie
Posts: 10

Loc: Puyallup WA
Reg: 03-16-13
03-22-13 06:47 PM - Post#2328678    
    In response to PaPa T

how is your oil pressure? If it goes to low it will cut the power to the fuel pump

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3090

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
03-23-13 07:41 AM - Post#2328756    
    In response to Adam144

  • Adam144 Said:
how is your oil pressure? If it goes to low it will cut the power to the fuel pump


It is common to see this written but it is not the way these TBI trucks are wired.

When the engine has oil pressure a redundant circuit supplies power to the fuel pump. This circuit goes through an oil pressure sensor/sender. This circuit is independent of the fuel pump relay.

This is very easy to test:
If you pull the fuel pump relay while the engine is running it should keep running. If it dies the oil sender or its wiring is bad or the engine lacks oil pressure.

If you unplug the oil sender while it is running it should keep running also. If it dies the fuel pump relay or its circuit is bad.


PaPa T, if you think the EGR may be the problem, disconnect and plug the vacuum hose to the EGR valve and take it for a test drive.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
chevrolet_kelowna 
Contributor
Posts: 229
chevrolet_kelowna
Loc: Kelowna BC
Reg: 11-22-07
03-23-13 11:16 PM - Post#2328980    
    In response to Chevytech

My 1991 GMC 2wd 350 took me over a month of troubleshooting figure out why are 10 minutes of warming up it would want to sputter out just like yours. After tuneup, timing, fuel pressure checks. we unplugged the egr valve and found the huge mystery problem. Ran great without it. Grabbed one the next day and never a problem since.

(I forget now whether you unplug it and plug the line with like a golf tee or what I don't remember but it involved just unplugging it and waiting for it to warm up and sputter but never did it again.

 
PaPa T 
Forum Newbie
Posts: 3

Reg: 03-19-13
04-05-13 11:35 AM - Post#2332940    
    In response to chevrolet_kelowna

Thanks guys, it was the EGR valve. Changed it and it's running like a champ.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3090

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
04-05-13 04:58 PM - Post#2333013    
    In response to PaPa T

You’re welcome, and thank you for letting us know what fixed it.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
Belairebabe 
Forum Newbie
Posts: 1

Reg: 02-08-14
02-16-14 11:56 AM - Post#2427354    
    In response to Chevytech

Have a similar prob but all the suggestions have not cleared the prob. 91 chev p/u, 350, auto,, idles fine on start up, runs down the road,, sputters and tries to die and then stalls on braking, almost like a vacuum leak,, tested all lines, hoses and parts dealing with vacuum and found no leaks but when engines starts to act up it's like the brake booster is robbing the motor of vacuum. Have replaced everything except the o2 sensor ( have changed egr and valve, iac, tps ,knock sensor ) have done ether test on all vacuum parts and am now severely frustrated,, any other ideas???

 
CowboyTrukr 
"3rd Year" Silver Supporting Member
Posts: 1969
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
02-16-14 12:38 PM - Post#2427366    
    In response to Belairebabe

Welcome to ChevyTalk. What's your fuel pressure?

Greg
'94 Silverado K2500 4X4 5.7 5spd Xcab LB. SOLD. :-(
'00 Contour SE 2.5 24V

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
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