88 Suburban wont idle

[88SuburbanMONSTER]

88 Suburban wont idle. Going down the highway, let off the throttle and it died. Timing was off and warped some intake valves. (found while trouble shooting.) Replaced all pistons, all intake valves, TPS, AIC, MAP, EGR, egr solenoid, coil, pick up coil, ignition control module, plugs and wires. Checked for vac leaks, checked fuel pressure (13#) I think that is good for this TBI. Rebuilt fuel regulator and TBI gaskets. Injectors seem ok, good spray. As you can see tons of money already. Any ideas?

[scotts62]

has to be either vacuum leak or fuel. have you put a vacuum gauge on it and see if the needle bounces around?

[ChevyTech]

Did you unplug the set timing connector when you set the timing?

Welcome to the board!

[88SuburbanMONSTER]

No Scott, I haven't put a vac gauge on it; but that sounds like a good idea. may take a day or so ; but I'll try that. As far as the timing advance wire, It seems to be close just by initial time, at least enough to keep it running. I just can't run it long enough to fine tune it yet. Thanks for your replies and I hope to get more ideas in case this doesn't resolve it.

[ChevyTech]

Unplug the hose to the EGR and see if it helps.


The next thing that comes to mind is that it may have valves (rockers) adjusted to tight.

If you used the method in the manual that tells you to spin the pushrod in your fingers when you were adjusting the valves, you could easily have them adjusted to tight.

If the parts are smooth, and you use good lube on reassembly, it is very hard to feel the point your reach zero lash when spinning the push rod. I only use the wiggle the push rod method when adjusting valves.

[88SuburbanMONSTER]

Rockers too tight may be a possibility and I will check that too on Thursday; but before I put the new intake valves in, It was running ok. Then one day after going down the interstate (8 miles) I lost the ability to idle once I let go of the throttle on the deceleration ramp. Has not idled since. Also puchased a vacuum gauge, fuel gauge, and OBD1 scan tool today; which I will try Thursday.

[ChevyTech]

Then one day after going down the interstate (8 miles) I lost the ability to idle once I let go of the throttle on the deceleration ramp. Has not idled since.

This sounds like an EGR valve stuck open.

There is a vent port on the EGR solenoid the people think should have a hose or cap on. It should be left open. Unplug the hose to the EGR valve and see if it moves to the closed position.

Here is information from an earlier thread on the same topic:

One nipple on the EGR solenoid should not have a vacuum line connected to it, because it is a vent. The earlier trucks had a sponge like filter on the vent nipple. It is fairly common to see the filter missing on older vehicles.

On the EGR solenoid, as the solenoid is de-energized (vacuum supply cut to EGR), vacuum would be trapped in the EGR if it were not for the vent passage, to let air in. As the EGR diaphragm moves, when the EGR valve is closing, air is drawn in through the vent.

[88SuburbanMONSTER]

In my attempt to fix this problem, I've replaced the EGR and the solenoid, air intake control, map, throttle position sensor, pcv, ignition control module, coil, pick up coil, plugs and wires, rotor, and cap. Not saying the new parts aren't bad; but I hope not. I will check on the vent hole though. Along with the other great advise.