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86 Will Only Idle - will not increase RPMs

hzl6cm

Well-known member
Joined
Feb 14, 2004
Messages
188
Location
Odessa, MO
Corvette
1970 Laguna Grey Convert., '04 Z06
I've got an 86 that will only idle, if I try to give it any gas at all it immediately dies. Here is a little background. When I got this car the guy was doing a little paint work, a little interior work and a little mechanical work all at the same time in a small garage so it had been off of the road for a few months. I could start the car and it would idle but would not accelerate at all, if I hit the gas it would die. I could drive it as long as I juste did it at idle. He had recently installed new fuel injectors and had a bad intake vacuum leak - I thought that was what was causing the problem. I fixed the leak (after replacing all of the intake gaskets I discovered it was the cold start injector - his kid had bent the bracket so it wasn't seated properly). But the car would still only idle, as soon as I give it gas it would die. Some of the spark plug wires looked bad so I replaced them and I discovered some bad vacuum hoses so I replaced all of them. Still no change except that it now starts harder than before (cranks fine and fires off of starting fluid but doesn't run on gas for long). Further info, the check engine light is on but when I hook up my scanner (Auto-Xray) it won't communicate with the computer.

Any ideas? I thought maybe the TPS but don't know how to check it if the computer won't talk with the scanner. I thought maybe the computer was bad but would it even idle then?

Thanks.

Kevin
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Couple things to check - MAF, connection to the ECU (a bent pin in the wrong place gave me a similar problem), TPS, timing, fuel pressure.

You can check the TPS voltage with a couple pins through the wiring harness - then touch your voltmeter to the ends of the pins. Take the readings using the top and middle wires. Should be .54v at idle and go up smoothly from there.

Pull the MAF and look for a broken wire.

Fuel pressure should be between 35 and 40 PSi at idle with the regulator vac. hose removed.

Timing should be 6* BTDC with the car warmed up AND the timing bypass wire disconnected (black or tan single wire with an inline connector that's somewhere near the brake booster or exhaust manifold on the driver's side).

Also, you may still have a bad intake leak somewhere...

[RICHR]
 

vetteboy86

Well-known member
Joined
May 26, 2003
Messages
2,760
Location
IN
Corvette
1986 Black "Indy 500 Pace car replica"
What is the condition of the other ignition components(cap, rotor, coil, module). I find your problem hard to believe, not saying it doens't exist, but thinking what could actually cause this. For the motor to stall the instant you crack the butterflies in the TB open leads me to believe that the fuel or spark stops. Fuel wouldn't be my first guess, perhaps spark. Either way, try the old paper clip technique. There is a key you can get from autozone, or you can use a jumper wire or paper clip to short terminals A and B on your ALDL connector together and read the flashes from your service engine soon light. If you get to that point most can provide you with the codes. You will see the service engine soon light flash sequences. The first thing it will do is flash once, then pause, then flash twice. This signifies 12, it will display code 12 three times. It will then go into any codes stored. Ex. three flashes, pause then four flashes would be code 34, it will display each code three times then when finished will go back to 12. Good luck and let us know what you find.
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Forgot to add one more thing to check - a big crack in the accordian hose between the MAF and the throttlebody. If you are sucking in a lot of air after the MAF has measured what should be in the engine, you'll kill the engine every time. Happened to me on another car - idled great but would stall as soon as you gave it ANY gas. Forgot about that until just now...

And if you fixed the problem, post so we know what you did...
[RICHR]
 
T

tdr1919

Guest
I had a 350 with bad hydrolic lifters that started and ran in neutral but died under load.
tom
 

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