Chevy & GMC Vans

My 350 TBI with 1995 heads and intake and 1996 short block has a high idle issue.It is still in the donor van because I want to resolve this before the swap.We have tried to scan the computer and the results are it will not commucate with the scanner.The TBI has cop car injectors lifted.We tried to swap in another computer and still the same thing.We swaped the heck out of it and did not find any vac leaks.

I wanted to fix this between the 27th and the 4th so I could take out the engine and trans to prepair it for the swap to Ole Yellar.

Does anyone have a wiring diagram for a 1989 Astro and what wire controls the idle??.I'm thinking I have a break in the wiring harness somewhere.Or it was miss-wired by the past owner.

The other thing going on is it does turnover quite afew times before it starts.It does run very strong other than the high idle.

Guys and gals-I do need your help on this one and I am completely open to all and any suggestions.I need to set a base line from which to work from for any further mods.

Gary, this isn't exactly what you are looking for but it's in the ballpark. http://www.autozone.com has repair guides for vehicle models up through '96.
the link below is for my '89 4.3L, it'll give you an idea of what they have online.
http://www.autozone.com/shopping/repair ... 52800a824a
You should be able to find the wiring diagrams for your 350.

Thank You for the links.I am not sure I am even asking the right questions. I mean without computer codes I am doing this blind.

Gary, I have the factory wiring manual for the 89 Astro. The book is large format, though, and it won't fit on my scanner. I'll xerox the engine control section and get that off to you.

check the site out, they have the wiring diagrams for engine controls, emissions and chassis all there

I will study those links and treat each wire on it's own.Seems like a big job until you scale it down to each wire I would guess.

But that will only I.D. why I can't scan the computer I would think(best guess)Still not sure why I have the high idle.What would be a list of sensors that could cause that??.Temp,02,??.Remember I did spray the heck out of it and never found a vac leak.

My gut reaction is the idle air control valve. either malfunctioning or the pintle is sticking.
I've added the IAC to my regular maintenance. I periodically pull it and clean the port and the pintle. It's not hard to get to.

other thoughts and questions:
I've had a sticky throttle plate produce a high idle.

Is the engine at operating temp or cold when idling high?

Gary, does the service engine light work? have you tried the paper clip to jump the AB terminals?
could be the scanner plug, or the contacts in the ALDL are munged up a bit and not contacting right.

Could also be that the data link isn't wired correctly or wired into the system at all.

kings-x59 wrote:other thoughts and questions:
I've had a sticky throttle plate produce a high idle.

Is the engine at operating temp or cold when idling high?

Both-it will come down some once at operating temp,but is still high.

kings-x59 wrote:Gary, does the service engine light work? have you tried the paper clip to jump the AB terminals?

I am going to try that.

could be the scanner plug, or the contacts in the ALDL are munged up a bit and not contacting right.

Smiliesafari wrote:Could also be that the data link isn't wired correctly or wired into the system at all.

I will trace that on Friday.The van is parked at a friend's repair shop which in a way kind of sucks to work on it.

Thanks guys,

Gary

Wiring harness aside-looks like I'll be measuring sensor values with a VU meter.

Anyone have those values for this engine's sensors?.

kings-x59 wrote:My gut reaction is the idle air control valve. either malfunctioning or the pintle is sticking.
I've added the IAC to my regular maintenance. I periodically pull it and clean the port and the pintle. It's not hard to get to.

I hear you loud and clear.I read another thread you where involved in the tech section about the IAC.I don't know what yr this TBI is because I believe this swap was miss handled by the owner before me.Is there numbers on the TBI that I could use to find out which yr this TBI is??.Thinking is a rebuild would be best just to be sure it was done the right way.

Gary,

Define "high" for me. What RPM are we talking about here? If you just guessing it's high, get a tach on there so we have an idea.

I seem recall my 91 p/u having what I thought sounded like a high idle. But watching the tach, not so much.

My 89 9C1 does the same thing.

Ok I am back on this issue.I am going back to reinstall the steering column tomorrow in the donor.Before I took it out for Ole Yellar,I started the engine and pulled the EGR connection off and it ran crappy like it is suppose to and cleared up once I put it back on and I pulled the IAC connector and it ran alittle higher like it is supposed to as well and when back down. some once I reconnected it. ](*,)I am going to have a really clear view of the wiring harness for the date link connector before I put back the steering column.So I will take a hard look at that.

The other question is has anyone realized a higher idle after doing the TBI mod's.??Seems the the owner before me smooth out the ridges and did do some porting to the TBI.