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Starts then dies unless gas held

racsluos

Well-known member
Joined
May 29, 2006
Messages
82
Location
North Vancouver, BC
Corvette
1987 Gold Coupe
Hi,

1987 Automatic Coupe, starts up and immediately stalls/dies unless given gas. Next best step after...?

INFO:
- Will continue to "idle" in Park at stable RPM with gas held down, as low as 900...releasing gas = instant stall
- Fuel Pressure good, fuel pump runs for 2 secs pre-startup as should
- Cap, rotor, plugs, coil = new

SUSPICIONS:
- Ignition Control Module ICM could be bad? Will see about getting tested.
- IAC? Something screwed up there not allowing enough air to idle?
- Injectors? If was injectors would I still be able to hold it running?
 

bosshogg

Well-known member
Joined
Jul 15, 2006
Messages
56
Location
Indiana
Corvette
1988 Coupe
My 88 did the same thing last week...my son had used it and topped off the tank the week before...I added 2 small cans of dry gas and the problem was solved. This happened to me years ago with a Trans-Am. I tore it apart and installed a new timing chain and gears...being that Pontiacs were notorious for timing chain failure...when done I still had the same results...would not stay running and backfiring unless I held the throttle steady...it was only then that the wife told me (excuse me, ex-wife) that she had just put gas in it before it started acting up...dry gas fixed it, but not the marriage!!!
Good luck...hope it is something that simple...Now it is back to my garage...my 99 Suburban has an intake manifold coolant leak...can't win
JOHN
 

racsluos

Well-known member
Joined
May 29, 2006
Messages
82
Location
North Vancouver, BC
Corvette
1987 Gold Coupe
Hey John, awesome tip, wouldn't have thought of that, though the problem did start happening soon after a fillup...hope it's that easy!

cheers

My 88 did the same thing last week...my son had used it and topped off the tank the week before...I added 2 small cans of dry gas and the problem was solved. This happened to me years ago with a Trans-Am. I tore it apart and installed a new timing chain and gears...being that Pontiacs were notorious for timing chain failure...when done I still had the same results...would not stay running and backfiring unless I held the throttle steady...it was only then that the wife told me (excuse me, ex-wife) that she had just put gas in it before it started acting up...dry gas fixed it, but not the marriage!!!
Good luck...hope it is something that simple...Now it is back to my garage...my 99 Suburban has an intake manifold coolant leak...can't win
JOHN
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,547
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
My guess is IAC is sticking or the EGR has a small piece of carbon in it!! If it's the EGR,Clean it with carburetor cleaner and get 2 gaskets and a Stainless Steel faucet screen from the Hardware store and sandwich it between gaskets on the exhaust side so it will break up the carbon small enough to go through the EGR pintail!!! Then you'll have no more Problems with it!! I've had to do this to allot of Older 350's and 4.3's!! :upthumbs junk!!
 

racsluos

Well-known member
Joined
May 29, 2006
Messages
82
Location
North Vancouver, BC
Corvette
1987 Gold Coupe
Good info thanks!

Will update tonight one way or another...

My guess is IAC is sticking or the EGR has a small piece of carbon in it!! If it's the EGR,Clean it with carburetor cleaner and get 2 gaskets and a Stainless Steel faucet screen from the Hardware store and sandwich it between gaskets on the exhaust side so it will break up the carbon small enough to go through the EGR pintail!!! Then you'll have no more Problems with it!! I've had to do this to allot of Older 350's and 4.3's!! :upthumbs junk!!
 

racsluos

Well-known member
Joined
May 29, 2006
Messages
82
Location
North Vancouver, BC
Corvette
1987 Gold Coupe
About to go readjust the TPS...
....I followed the FSM procedure with all the steps for minimum idle adjustment, so should be good.

Short version of all this is that while I was hunting for the cause of my post-tuneup miss/stutter, I was manually moving/holding the throttle mechanism a lot while peering into the engine. Only thing I can come up with is that I must have tweaked something there such that the idle screw(which had never been touched in 19 years) needed to be screwed in a bit for minimum idle to not sink too low.
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,547
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
can't express the relief I'm feelin now
fixed with the idle stop screw, will post details after dinner
If you turned that little screw on the throttle body, it will act up again!!:upthumbs
 

racsluos

Well-known member
Joined
May 29, 2006
Messages
82
Location
North Vancouver, BC
Corvette
1987 Gold Coupe
If you turned that little screw on the throttle body, it will act up again!!:upthumbs

Still going to go indepth on the IAC, EGR, and general vacuum lines under the hood, but I'm confident with this for now...at least I can drive it a bit while there's Vette weather here!
 

bosshogg

Well-known member
Joined
Jul 15, 2006
Messages
56
Location
Indiana
Corvette
1988 Coupe
Just wondering if you got your problem corrected and what caused it...we have about 3 weeks left of "Vette" weather here...
As always..."Enjoy The Ride"
John
 

racsluos

Well-known member
Joined
May 29, 2006
Messages
82
Location
North Vancouver, BC
Corvette
1987 Gold Coupe
Just wondering if you got your problem corrected and what caused it...we have about 3 weeks left of "Vette" weather here...
As always..."Enjoy The Ride"
John

It's been running fine since adjusting the idle stop screw...I have huge fall/winter plans for it, including plenum swap, runners+manifold(if I can afford them), cat back exhaust, and sound insulation in the interior. When I do the intake stuff, I will be taking off the IAC and cleaning and checking it, as that's the most likely culprit. My vacuum seems good, as well as EGR.
 

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