New truck and engine rebuild

[noom14921992]

Hello all, This is my first post. I will try and make it quick.

I have a 1989 Chevy C1500 with the 350 TBI and 700r4 transmission.

I got the truck for 500$ because it had a blown head gasket. When i got it, it cranked and ran fine. just with the blown head.
My friend who said he knew what he was doing helped me.

Long story short, it does not run by itself anymore.

We replaced all the gaskets, timing, water pump, and did a tune up.

We can start the truck as long as you give it 1/2 throttle. if you take your foot off the gas it dies.
if you keep gas on it it will stay running until you uncrank or take foot off gas.

1. I verified that all the vacuum tubes are connected correctly.
2. everything is torqued down to spec.
3. compression on all cylinders was within specs
4. TBI is getting fuel
5. Spark plugs are getting spark

I am not sure what direction i need to look.
I think it could be a tooth or few off on timing. But i was told that even if it were off on timing that the truck would still idle.

What do i need to check for no idle?

I look forward to getting some good help.

Thanks!

 

[Schurkey]

1. Are you sure the lifter preload is properly set? Not too tight?
2. Are you sure the plug wires are going to the correct cylinders, and firmly attached at both ends?
3. Verify ignition timing. Disconnect the one-wire EST connector, timing at idle should be "0" but folks often add a couple of degrees of advance. 0--4 degrees advanced should be fine. "A tooth or few off" will NOT run right unless you spin the distributor body around to some crazy angle. You'll have to disconnect the battery after checking the timing, because disconnecting the EST wire will set a code that has to be cleared.
4. What is the fuel pressure?
5. How old are the distributor cap, rotor, plug wires, spark plugs, fuel filter, air filter? Does the EGR work properly and shut-off at idle? Does the PCV system work properly?
6. You said you "replaced the timing". Do you mean you replaced the cam timing set--gears and chain? Are you sure you got the cam properly timed? Did you degree the cam, or merely cram the gears on "dot-to-dot"? Is this a multi-keyway timing set, and maybe you used the wrong mark when aligning the crank gear?
7. What is the actual cranking compression pressure? "Within specs" covers a lot of ground, and would also depend on your altitude among other variables.
8. Connect a scan tool, look for "codes" but also verify all the sensors and computer outputs. How old is the O2 sensor?
9. Have you done a cylinder-balance test to see which cylinder(s) are the problem?
10. You replaced "all the gaskets". Did you replace the throttle-body to manifold gasket? Common problem. Did you use the CORRECT intake manifold to cylinder head gaskets, with the blocked rear coolant passage?

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[1997]

wow, nice "quick set" troubleshooting guide.

 

[noom14921992]

Update:
I put a timing light on the truck and found that when you give it gas it is perfectly in time. Or at least it lines up with the mark.
When you release the gas the timing drifts by about .5 to 1 inch on the harmonic balancer.
The drift is towards the driver side of the mark. so it drifts clockwise.

I am not sure what this means, but i am sure this is something that i should adjust.
Is that something i can do with the distributor?

thanks!

 

[Schurkey]

Update:
I put a timing light on the truck and found that when you give it gas it is perfectly in time.

With or without the one-wire EST connector disconnected? What RPM is "give it gas"?

Or at least it lines up with the mark.

"It" lines up...what "it" are you talking about? What mark are you talking about?

If this is the line on the damper, and the "0" on the timing pointer, AND the 1-wire EST connector is disconnected, the only part that concerns me is the RPM. You should be at "0" or TDC at idle.

IF (big IF) you've unhooked the EST connector, one wonders if the ignition module is failing, so that the timing isn't stable. Other potential causes are a sloppy timing chain, worn distributor bushings or distributor gear.

If you have not unhooked the EST connector, your timing is way the hell off.

When you release the gas the timing drifts by about .5 to 1 inch on the harmonic balancer.
The drift is towards the driver side of the mark. so it drifts clockwise.

The scale is on the timing cover, not the damper. I don't know what this means. If the line on the damper moves a half-inch to the driver's side of "0" on the timing pointer, AND the EST connector is unhooked, the timing is WAY RETARDED. Which doesn't seem right since you've done a tune-up on this thing. You'd have checked and adjusted the timing when the distributor went back in after the head gasket replacement.

 

[TuckerDog]

Have you checked what the rpm is at idle? Check to to make sure the fuel & air is getting to the intake manifold. Bring up the idle speed, make sure fuel & air is getting to the intake. Hopefully that'll help a little bit. And also check the ignition to make sure your getting spark to all the cylinders.