**need Help!!!*** - The 1947 - Present Chevrolet & GMC Truck Message Board Network

zr8td2k · 03-23-2003, 07:03 PM

Hey everyone...i need some help form peopel who know these trucks. I have a 2wd 87 gmc.5.7L T.B.I.

First Problem - I changed the plugs/wires, cap ,rotor, PCV valve and the truck ran great. Next day i go to drive it and i start up the hill and shuts off for a second then comes back on. Almost snapped my neck off. Check engind light came on. Showing A code 42. Electric spark contol system. Book says to check to replace HEI Module. I did this and it still does it. The book ssays this is directly linked to the ECM/computer under the dash. Should i get a new ECM? I also checked all the plugs and wire and common things to make sure they were in the correct order. Everthign checks out.

Second problem - In lew of the first problem. I put a new IAC in and when i started the truck it was idiling hihg then went normal. Then the truck stalled and fuel came out of the TBI by the linkage are all over the manifold. Buddy said the bushungs for the butterfly may be worn and gas is leaking through there. Any idea?

thanks for all the help ( hopefully) I am forced to drive my show truck everday now so i have to get this thing fixed!!

**swervin ervin** · 03-23-2003, 07:10 PM

I'm in no way a computer person on the 87 TBI trucks, but it does sound as though you may have a computer going out. I can't say for sure though. I don't know of a way to check the things, but I'm sure there may be a way. One way would probably take it to the dealer or similar and have them check it on a machine. Another way, and the way I do most things is just replace it and hope it fixes it.

I would try to find a used at a junkyard and see what happens. It would be much cheaper than buying a new one.

On the other problem. I don't know. For sure it sounds as though the fuel isn't stopping when the engine is stopped, like it should. It may very well be associated with the computer too.

Wish I knew more.

Good luck with it.

apstguy · 03-23-2003, 10:34 PM

I have heard the bushings on the butterfly valves go bad often on TBI trucks. Try replacing it.

*racedvl* · 03-23-2003, 11:17 PM

I have the same problem on my 87 4x4 burb. I have about pulled out all my hair. I have let the truck sit for around a year now, am this week I am gonna (gasp) pay someone to repair it. . . (shame)

03-23-2003, 07:03 PM	#1
zr8td2k Registered User Join Date: Jan 2003 Location: coatesville pa Posts: 13	need Help!!!* Hey everyone...i need some help form peopel who know these trucks. I have a 2wd 87 gmc.5.7L T.B.I. First Problem - I changed the plugs/wires, cap ,rotor, PCV valve and the truck ran great. Next day i go to drive it and i start up the hill and shuts off for a second then comes back on. Almost snapped my neck off. Check engind light came on. Showing A code 42. Electric spark contol system. Book says to check to replace HEI Module. I did this and it still does it. The book ssays this is directly linked to the ECM/computer under the dash. Should i get a new ECM? I also checked all the plugs and wire and common things to make sure they were in the correct order. Everthign checks out. Second problem - In lew of the first problem. I put a new IAC in and when i started the truck it was idiling hihg then went normal. Then the truck stalled and fuel came out of the TBI by the linkage are all over the manifold. Buddy said the bushungs for the butterfly may be worn and gas is leaking through there. Any idea? thanks for all the help ( hopefully) I am forced to drive my show truck everday now so i have to get this thing fixed!! __________________ ~EXCLUSIVE STYLES~

03-23-2003, 07:10 PM	#2
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	I'm in no way a computer person on the 87 TBI trucks, but it does sound as though you may have a computer going out. I can't say for sure though. I don't know of a way to check the things, but I'm sure there may be a way. One way would probably take it to the dealer or similar and have them check it on a machine. Another way, and the way I do most things is just replace it and hope it fixes it. I would try to find a used at a junkyard and see what happens. It would be much cheaper than buying a new one. On the other problem. I don't know. For sure it sounds as though the fuel isn't stopping when the engine is stopped, like it should. It may very well be associated with the computer too. Wish I knew more. Good luck with it. __________________ Mike 1985 Chevy C-10

03-23-2003, 10:34 PM	#3
apstguy LED King Join Date: Jan 2003 Location: Sacramento, CA Posts: 2,087	I have heard the bushings on the butterfly valves go bad often on TBI trucks. Try replacing it. __________________ Tyler 1985 C10 305 w/ Bowtie OD TH700R4 3.42 LSD 202,000 miles 2006 Ford Focus ZX3 5-speed Stick 2016 Chevy Spark EV Gone: 2002.5 VW GTI 24v VR6 Gone: 2008 VW R32

03-23-2003, 11:17 PM	#4
racedvl Account Suspended Join Date: Jan 2000 Location: Woodstock, IL Posts: 7,020	I have the same problem on my 87 4x4 burb. I have about pulled out all my hair. I have let the truck sit for around a year now, am this week I am gonna (gasp) pay someone to repair it. . . (shame)



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