No idle...need help

[barrie2777]

I changed the ignition module because there was no fire. Now it starts but wont idle. Please help....

[68 P.O.S.]

Is it only at idle, or will it run if you hold your foot on the gas? It could be timing, carb, distributor, vacuum leak, fuel restriction, or a combo of everything. Please give us a lot more background info on your truck...including any work done to it.

[barrie2777]

I have a 1987 r30 with 87000 original km. The only
Electronic thing changed was the ignition module which i did a few weeks ago. The truck starts and run as long as revs are up. Return to idle and it stalls. Ir was running fine. I had not used it for several weeks. It had no fire when i went to it. Changing the ignition mudule made it start right away but tgat was when the idle issue came up.

[HO455]

Going with my proven theory of "Always go back to the last thing you messed with...). I would check the timing first, then look for a vacuum leak if that doesn't solve the problem.

[68 P.O.S.]

x2, I agree with HO455

Your problem could be a couple things, however, always start with timing as it's essentially your engine's baseline. If timing isn't set correctly from the get go, nothing else will be correct either. I obviously don't know your skill level, so not trying to talk down to you, but do you know what the timing numbers are to set it at and do you know what your engine is currently at? After checking timing, I too would move on to looking for vacuum leaks. Check every hose for proper connection, damage, and wear. Vac leaks can be a real pain and make your engine run like crap.

[Fbks_Cruiser]

I agree. Is it possible that while poking around to swap the ignition module you may have inadvertently disconnected a vacuum line that didn't get hooked back up?

Stock air cleaner? Maybe one of the vacuum lines connected to it for the hot-air door didn't get hooked back up correctly after you reinstalled it? Vacuum line to the distributor advance pulled off?

[barrie2777]

I cant see timing being the issue since i have been driving this truck for years. A vacuum line might be the issue. Ill check those. Thanks

[68 P.O.S.]

Have you checked the timing tho?

[barrie2777]

I have not checked the timing. Ill do that also.

[68 P.O.S.]

You should, off timing can make your engine do all kinds of wonky things....like disguise itself as a carb problem. Let us know what it's set at.

[HO455]

I should double check. The ignition module that you replaced was on an HEI? Are all the plug wires on the correct posts? Are you sure there is absolutely no chance that the distributor turned during the replacement process? Please don't take these questions the wrong way I just want you back on the road and not wasting time like I have done so many times learning lessons the hard way. I drove my Burban about 1500 miles with the old 305 and it wasn't until I swapped the distributor to the new engine did I find out #4 and #7 plug wires were swapped. No wonder it was gutless.

[barrie2777]

Not HEI. The coil is beside the dis cap.

I labled the wires and posts before removing them then double checked placement. The rotor was removed to replace the module.

[geezer#99]

Originally Posted by barrie2777

Not HEI. The coil is beside the dis cap.

I labled the wires and posts before removing them then double checked placement. The rotor was removed to replace the module.

What exactly did you change?
We need pics to know exactly what you have.

[68is4me]

I would assume that it is a stock fuel injected motor. If it idled fine before the module was replace then go back and retrace your steps. Those older fuel injected motors might require an idle relearn and timing relearn.

[barrie2777]

Ran fine, idled fine prior to module change. My mechanic friend says I need to drive it for 10 -15 minutes for it to relearn. Might have time today to try that simple solution.

[barrie2777]

Originally Posted by geezer#99

What exactly did you change?
We need pics to know exactly what you have.

How do i post photo here?

Now battery seems to be going dead .

[geezer#99]

Originally Posted by barrie2777

How do i post photo here?

Now battery seems to be going dead .

http://67-72chevytrucks.com/vboard/s...d.php?t=712252

[barrie2777]

Photo of carb and distributor cap on r30 350cu in

[jdbas71]

If you didn't pull or loosen the distributor to change module than timing shouldn't have changed from where it was.

[68 P.O.S.]

Originally Posted by jdbas71

If you didn't pull or loosen the distributor to change module than timing shouldn't have changed from where it was.

Assuming timing was correct to begin with.

[barrie2777]

Originally Posted by jdbas71

If you didn't pull or loosen the distributor to change module than timing shouldn't have changed from where it was.

Exactly my thoughts. I think until i guve it a "learning" ride ill wait before changing more components.

[HO455]

If your engine is anything like my 91 4.3 those plastic vacuum lines for the tranny control and PVC are FRAGILE at this point in time. Give them a good going over. I found a hole in my PVC hose on the bottom of the 90* out of the carb. Gave me fits for a couple of hours one day.

[barrie2777]

Originally Posted by HO455

If your engine is anything like my 91 4.3 those plastic vacuum lines for the tranny control and PVC are FRAGILE at this point in time. Give them a good going over. I found a hole in my PVC hose on the bottom of the 90* out of the carb. Gave me fits for a couple of hours one day.

Would that effect the idle?

[HO455]

Yes it would. Your TBI unit won't be able to compensate for air entering into the intake from anywhere but through the throttle body. A leak makes the idle mixture lean. You may have a combination of a vacuum leak and the computer wanting to relearn that is causing your issue. You should be able to find a leak by spraying carb cleaner on the hoses when it is running and listening for a change in the engine speed. There are numerous videos out there on this if you are not familiar with the process.
Good luck.

[barrie2777]

Originally Posted by HO455

Yes it would. Your TBI unit won't be able to compensate for air entering into the intake from anywhere but through the throttle body. A leak makes the idle mixture lean. You may have a combination of a vacuum leak and the computer wanting to relearn that is causing your issue. You should be able to find a leak by spraying carb cleaner on the hoses when it is running and listening for a change in the engine speed. There are numerous videos out there on this if you are not familiar with the process.
Good luck.

Something i noticed today...the gasket on the bottom of the ring around the carb is not there anymore but is a pile of pieces sitting near the valve cover. Could the absence of this gasket cause the problem?