1988 Chevy 1500 V8 runs rich, won't idle right. IAV? (Page 1/2)
starlightcoupe JAN 19, 07:45 PM
I started our 1988 Chevy pickup with a 350 V8 and throttle body injection. The truck has always been a little hard to start in cold weather but I started it today for the first time in several months. The engine ran rough as it always has until it warms up but this morning the engine began to rev to around 2500 rpm and thick black smoke came from the exhaust. The engine died when I tried to move the truck and refused to start but finally caught and I was able to move it. Since I've never worked on a TBI before, I found my book and the IAV or idle control valve or idle air valve seemed to be the culprit. I pulled the plug to it while the engine was running and it had no effect at all. Both of my books have some tests to perform but the tests were simple resistance measurements which didn't prove much other than my IAV coil is within parameters.

Any ideas?? Tomorrow is Sunday and we live in BFE so I'd have to drive 55 miles to get another IAV and hope for the best.
jaskispyder JAN 19, 09:40 PM
check engine light come on? Plugs, wires, cap, rotor all good?
starlightcoupe JAN 19, 11:59 PM

quote
Originally posted by jaskispyder:

check engine light come on? Plugs, wires, cap, rotor all good?



Yes to all your questions. The SES light was on when I bought the truck but this rough running and rich mixture thing began about three minutes after I started the truck today. Until today, the truck has run very smoothly This is a totally new problem. The plugs are new, wires, new cap and rotor are fine and dandy. I don't have a code reader and I needed the truck immeditately this morning because my wife didn't tell me she had arranged for me to get a pickup load of dirt at 9am so i tried starting the truck that hadn't been started since last September, it didn't want to start, I ran a 100' power cord to the truck, brought my charger and charged the new Diehard I bought last June. (nothing is running it down--I checked current draw (probably ECM and radio) and it is much less an 1ma)

Can a bad IAV cause the rich mixture? I unplugged the electrical connection from the ECM to the IAV and there was no change in the way the engine ran. The Haynes test is to plug in the wires to the IAV, turn on the ignition for 30seconds and removed the plug. Then check resistance to both sides of the IAV coil. I get what the Haynes manual said so my only thought was that the valve itself-- an electromechanical device--may be sticking or faulty.

I bought this truck from a relative who totally screwed up the electrical system under the dash and under the hood. Wrong wires, broken this or that, totally screwed up brake light/stop light switch and much more. Despite this, I don't think there is a problem with the wiring.
jaskispyder JAN 20, 10:01 AM
You don't need a code reader. You can check the codes just like in a Fiero.
http://www.fiero.nl/forum/Forum10/HTML/000183.html
starlightcoupe JAN 20, 01:11 PM
There is much more to this sordid tale and I know I can check codes by counting the blinks for the SES light and looking it up in my manual. It was cold and I have a bad medical condition that kept me from doing much more than what I did to try to start the engine. My wife was actually going to get the dirt and spread it because I can't do it. Thanks for your help--i appreciate it.
jaskispyder JAN 21, 09:07 AM
It would REALLY help to have those codes.
carnut122 JAN 21, 09:32 AM
^^^^^^^^^^^ I agree. The codes will give you a hint if you're barking up the wrong tree.^^^^^^^^^^^
starlightcoupe JAN 21, 07:26 PM
I have a relatively simple surgical procedure to be done tomorrow morning and it could potentially result in something major if not done soon. My wife scheduled the dirt pick up without telling me she'd need the truck. Any kind of movement is torture for me and I wanted to read the codes but it is very painful to just get into the truck. The surgery is scheduled for tomorrow morning and within a month, I should be back on my feet "gooder then new."

The dirt guy will deliver for more than the dirt costs but that is the price one pays for procrastination. When I feel up to it, I'll check the trouble codes and hopefully you guys Carnut and jackiespyder will still be in the mood to help.

Thanks to both of you. i really appreciate your offer to help and hope I didn't seem ungrateful.

Richard
starlightcoupe FEB 02, 11:26 PM
Just got on my feet well enough to check codes. It returned a code 15 which is coolant sensor but that doesn't make much sense to me given the choke symptoms and running very rich.

Going back to my original diagnosis, is running rich a symptom of the Idle Control Valve?

[This message has been edited by starlightcoupe (edited 02-02-2013).]

carnut122 FEB 03, 12:22 AM

quote
Originally posted by starlightcoupe:

Just got on my feet well enough to check codes. It returned a code 15 which is coolant sensor but that doesn't make much sense to me given the choke symptoms and running very rich.

Going back to my original diagnosis, is running rich a symptom of the Idle Control Valve?




If the computer thinks the engine is cold, it will run rich and /or in open loop mode. I'd start with the coolant sensor and go from there. I'm glad you're feeling better!