HELP!! 97 5.7L DIES AT IDLE or DECELERATING???

[TravelPilot]

I have a 5.7L in a GMC Van Converted to a Class B, it dies when idling, and when letting off the gas 3 times today. Then it takes a few tries to restart. This just started yesterday. I changed the Fuel Fiilter and put Octaine booster in with no luck. Could it be the fuel pump or what have you found it to be.

It sucked when it dies right in front on 2 cops and I blocked the whole turn lane 🙂 Atleast no one could honk or get road rage with the cops there. They were even nice enough to wait til I got it started.

[Handbasket]

Thanks for closing the loop. Having the solution here in the archives may help some poor soul later.

Jim, "I'm not hard of hearing. I'm hard of listening."

[TravelPilot]

It was the Fuel Pump and I had it replaced. Solved the problem immediately.
Thanks for the help

[ol__grouch]

TravelPilot wrote:
I have a 5.7L in a GMC Van Converted to a Class B, it dies when idling, and when letting off the gas 3 times today. Then it takes a few tries to restart. This just started yesterday. I changed the Fuel Fiilter and put Octaine booster in with no luck. Could it be the fuel pump or what have you found it to be.

It sucked when it dies right in front on 2 cops and I blocked the whole turn lane 🙂 Atleast no one could honk or get road rage with the cops there. They were even nice enough to wait til I got it started.

How many miles on the unit as a whole? I think you have a multiport injection system. I'd suspect the fuel pump assembly due to age. Do you run it below 1/4 tank much? Any problems with the fuel guage? Is the your CEL (check engine light) lit? GM had some problems with injection systems back then on the 4.3 and didn't fix it until 2002. The 350 though had a different injection system.

Personally, I'd hook up a remote fuel pressure gauge and see what pressure you have when it dies. I'd put money on the fuel pump starting to fail. Besides dying on you, it may bog at times when not enough fuel is getting to the injectors. If it does turn out to be the fuel pump, when you take it in for repair, run your fuel tank down. Ideally for the mechanic, you want around 1/8 of a tank. The mechanic has to drop the fuel tank and the less fuel the better.

[michigan]

I also have a 97 Express. What you describe could be your fuel pump I change mine out and my van runs great.
You need to have a fuel pressure check or the next time its hard to start pour a little fuel down the throttle body to see if it start right up. If you determine that it is the fuel pump, I got the best price at paartsgeek.com

[BruceMc]

Our '93 suffered similar problems and after a bunch of troubleshooting and part replacement, it came down to the $18 temperature sensor located near the water hose connector on the intake. Our Daughter's '94 Saturn also suffered this issue.
If you are getting poor mileage as well - I'd suggest replacing this sensor.

These can be tough to troubleshoot, and throwing parts at it can be the easy way to do it, albeit somewhat expensive unless you happen to find the right part early on.

[ernie1]

On my Ford E350 it did the same thing your GMC was doing and it turned out to be the throttle position sensor. Don't know if it's the same as a idle air control valve or not. Anyhow when it dies on you and doesn't seem to want to start, try depressing the accelerator pedal just a little bit and hold it down while turning the engine.

[CShells]

The Chevy Express/GMC Savannah line is infamous for a random stalling problem. I found many online discussions about it the last time I was shopping for a used van.

[ronfisherman]

Moved from Class C/B+.

[j-d]

Based on the OP, mentioning 1997 5.7L, I went to RockAuto (easiest place to look up a part without having to "add a vehicle to my garage" like AutoZone) and since this is an RV forum chose "Express 3500."
That netted TBI and an IAC valve that looks like

That IAC looks like the one on the 1996 5.7L EFI in our boat. I replaced it because about one slowdown in 100 or more, engine'll quit. Mechanic with a scanner (different than automotive because of MerCruiser's adaptations of a few systems) has never found a clue. Cleaned IAC a couple times before I ordered one from BoatFix and swapped it. Now it quits one slowdown in 200 or more but I don't think the IAC really addressed the problem. As I recall, the TBI was held with Torx Head screws, so check before you go after it.
Still, if IAC has never been at least cleaned (I used Throttle Body Cleaner, but the manual says NOT to clean one but replace instead), the OP might find it would help. The IAC was not as gummed up as were the passages it controls. There's also Throttle Body Service (cleaning) that might help here.

[Golden_HVAC]

I guess it might help to know if you are talking about a 1985 or 2005 or what year.

If the fuel filter was plugged, mainly it would feel like you are lacking power while going full throttle getting onto the freeway, or while climbing a mountain. At idle, a plugged fuel filter will not starve the engine for fuel, only when about 1/2 throttle or more, until it is really plugged. Then it would not run at all above idle.

My guess? I really don't know if it is a carburetor problem, vacuum line, or what, it would really help to know the model year. Is it a 1500 series, 3500, was it hot out, cold, going up a hill, downhill? Did you have the A/C on? Did shutting off the A/C prevent it from stalling?

You might have a A/C compressor problem, and the carburetor idle screw is set to run 800 RPM while the van is in gear but stopped, without the A/C on, but A/C on can slow it down a bit. If the compressor is bad, it could stall a carburetored engine, but not normally a fuel injected one (with a computer that will open the throttle to keep the RPM at around 750 - 775 RPM all the time.

So?

Fred.

[jwoods61us]

OP, you don't state, but if it has TBI, this kind of behavior is identical to an IAC (idle air controller) failure. You can run it all day long with the throttle plates open, but when they close the IAC fails to let in any air and the engine dies. It is a cheap easy fix, stop by an O'Reilly and pick up a new one. Clicky

[carringb]

Check for major vacuum leaks. This affects the ability of fuel pressure regulator to function (as well as the idle air controller).

Once you rule that out, you probably need to verify fuel pressure. If you have never changed the fuel pump before, you'll probably need to.

[RoyB]

My FORD F150 did that once after I had the battery removed for an hour or so running some new cabling.

I noticed right away the IDLE RPMs was low but there isn't any way to adjust this with the computerized vehicles. The manual said it should relearn the proper setting but for some reason mine wouldn't do that after a few days.

I ended up having to take it back the dealership and let them reset the idle on their computer for $90 of course.

Don't know if this is your problem or not - It did fix me up ok...

Roy Ken