wont idle

[Martin]

1987 gl w hitachi carb. randomly died a few times on bumpy roads, some with puddles. everytime it would fire up but idle rough/ or die without pushing on the gas pedal. a couple of times it was really rough and wanting to die until i really revved it up and it gave a bit of a backfire, then it was perfect again. disty cap was dry everytime. changed the fuel filter & pour carb cleaner and seemed to be doing fine. then it happened again and it's not "fixing itself" put new plugs, cap, rotor, sprayed for vacuum leaks, egr seems to be springing back as it should. was able to idle, took it for a spin around the block and barely made it back. cold start up seems to work (choke) and pushing on the gas to rev it can take it up smooth all the way to the redline, but for the life of me it wont idle... rough, jumping revs, or just dies. how can everything work so well, but not at idle? carb? lacking fuel at idle? help! thanks.

[[HTi]Johnson]

Could the timing have jumped? Or even the right side belt break? Happens sometimes and it will still run, because the left belt powers the cam that the disty is attached too.

 

Does "wobble" when idling, like half of it is firing? Just my 2 cents.

[ivantruckman]

Look for the 02 sensor wire , make sure it didnt touch the cat and melt. my craptachi did the same thing "86 gl sedan" i re'hooked the wire and it ran perfect. i do also beleive that they had an idle solonoid , check for power to it, or even the engine ground straps. the ground is more likley the problem

[Skip]

sorry Ivan -> 87 if it has 4wd will not have an 02 sensor

not in the US anyways, no ECU either.

 

Martin, on the front of the carb is a hexagon protrusion

with a single wire emanating from it's end.

 

This sir, is the Anti Diesel Solenoid (ADS).

It's function is to prevent "run on" after switching the ignition to off.

It does this by shutting off the fuel flow to the idle circuit.

 

This sounds like one (1) of your problems.

The wire to it can break right at the solenoid.

 

The power to it should be checked.

It will "click" when the key is turned on if it is operating.

The valve inside may be stuck but that is rare.

 

If the electric choke is functioning properly the ground is intact and not the problem.

 

If the choke has power and the ADS does not,

you might try jumping a wire to the ADS from the choke to

verify the problem.

 

By chance have you looked for a fuel filter under the

car beside the fuel pump?

 

Hope this helps.

[Martin]

the timing could have moved, but doesn't seem loose... and I can't get it to idle to check it. it's definitely firing on all 4 cylinders.

 

 

skip is right about the lack of o2, as it's not a feedback carb, no ecu to get codes. the fuel filter under the car by the fuel pump is the only filter. i will check the ADS, something like that seems to be more likely.

[Martin]

so there is the connection that runs the ignition power to the carb. there are 3 different wires... 2 of them are at 12 volts, and 1 is at 5volts. the 2 at 12 volts will both cause clicking when power is added to them. one being the ADS at the front, the other on the drivers side of the carb. Then the 5 volts is what heads over to the passenger side (choke?), which seems low but it works.

 

 

any other ideas? other components with vacuums or thermosensors that would prevent idling.