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Out of ideas.. still idles like crap

MrSchaeferPants

MrSchaeferPants

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Posted a few times.. no info. Been trying to figure this out seems like forever now.

Q-jet M4MED 17085226 - GM Goodwrench 350 stock (stock carb on originally 305 motor)

Truck idles like crap, dies. Starting from cold it's just fine, but once that choke plate opens fully it's done. If I give it throttle it's fine. Something to do with the idle. I've ruled out timing/distributor, vacuum leaks. I can't figure out this lean symptom. A/F mixture screws have no effect. Even took them out and cleaned them and sprayed cleaner in the holes. Carb is 'mostly' rebuilt, and clean.

What affects idle. I mean Everything. idle circuit, jets, ports, choke/choke plate/linkage, throttle plate/linkage. I manually close the choke plate with my finger it smooths out, RPMs pick up.

Only thing I can think of perhaps, and I guess this will be my last ditch hope, is tomororw I'm removing the air horn and trying to blow out all the passages, since I didn't do that when I 'rebuilt' it. Brake cleaned them, but no compressed air since I don't have a compressor, I'll buy a can of canned air I guess. My only reasoning for this is intermittently I can't see the right (passenger side) venturi spraying any fuel. Well not spraying but I can't see any moving around.

Perhaps first I'll steal the Edelbrock off of my Blazer to see if it runs right, if it does at least I've for sure narrowed it down to the carburetor.
 
I thought you were going Edelbrock anyway???? If you don't need to worry about smog, or can at least hook up all the vacuum lines like original, dump that CC carb anyway. Then go from there. Really, you're wasting you time with that carb. Not that it can't work, it's just that eventually you should dump it anyway.

I can mail you my old CC carb. I don't think the choke was working right though. It did operate fine though, ran good. You can try it, then send it back lol.
 
K85 Octane said:
I thought you were going Edelbrock anyway???? If you don't need to worry about smog, or can at least hook up all the vacuum lines like original, dump that CC carb anyway. Then go from there. Really, you're wasting you time with that carb. Not that it can't work, it's just that eventually you should dump it anyway.

I can mail you my old CC carb. I don't think the choke was working right though. It did operate fine though, ran good. You can try it, then send it back lol.
Click to expand...

It's not really a CCC. It only has a (bypassed) ESC. Other than the dual capacity pump, nothing's electric. I'd love to keep the quadrajet, but if I swap the Ebrock on it and it runs fine, I might keep that on for the time being so I can drive it already.
 
can't speak much about the edelbrock and offroadabiltiy, but my cousin has an 800cfm (iirc, not sure) on his 383 and climbs mountains with it. Meaning, it doesn't bog enough for him to switch back. Just a thought, try it out, might be a whole new truck :) Sadly, it's been short a motor for about 7 years. A new 383 is in the garage, for about 4-5 years :doah: Pic whore

22 059.jpg
 
Ok. So I'm leaning towards timming. Replaced the carb with the Edelbrock. It still barely runs, and back fires. This is with it set anywhere from 0-16 degrees. It seems the more I advance it, the better it runs, but no where near good. Distributor has been replaced with the the one out of the blazer, plugs are new, plug wires were new, but I bought the cheapo ones, so I figured that might be it so I took the ones outa the blazer, made no difference. My only other thoughts is the damper or timming chain. One of them must be off, cause I know I'm at least on the compression stroke, double checked. The more I advance it (heading towards 20+) it SEEMS to run better, meaning I can at least get it to start. What are symptoms from a misaligned timming chain? And since this was a crate motor, whenever it was put in, it should have come with a damper right, so I couldn't have the wrong one, and it can only be installed one way because of the keyway right. I've been looking online for days, and have also found quite a bit about the damper degrading and shifting. Though I'm not sure if that does or even can apply to me.

So should I remove the timming plate and check it first, or figure out what direction the keyway should be relative to the timming mark for my application, since that I can do w/o taking anything apart.
 
Another thing that bothers the hell outa me is if it was ignition/timming. Why would it have smoothed out (seemingly) when I had the Q-jet on it, and gave it some gas, or closed the choke. If it was a carb issue that should have went away when I put the Edelbrock on.
 
With the Q-jet, your throttle bushings are probably worn enough to allow air to come in. When you cleaned it it likely removed the gummy varnish that was helping it seal. Closing the choke plate manually decreases the amount of intake air...in effect you're correcting the idle mixture by closing the choke plate a little. The fact your mixture screws aren't hardly doing anything is another clue.

As for how it is now, it sounds like the distributor got dropped in and is off by one tooth.

You can get Q-jets re-bushed. I'd do that before running an Edelcrap.

Rene
 
Does the thing have the EGR valve on it ??

If so make sure that its not leaking, as in remove it and install a blockoff or a new valve.

A leaking EGR valve will make the engine run like crap especially at idle.

Just a thought

Snowy
 
tRustyK5 said:
With the Q-jet, your throttle bushings are probably worn enough to allow air to come in. When you cleaned it it likely removed the gummy varnish that was helping it seal. Closing the choke plate manually decreases the amount of intake air...in effect you're correcting the idle mixture by closing the choke plate a little. The fact your mixture screws aren't hardly doing anything is another clue.

As for how it is now, it sounds like the distributor got dropped in and is off by one tooth.

You can get Q-jets re-bushed. I'd do that before running an Edelcrap.

Rene
Click to expand...

The throttle bushings werent too terribly bad. I played with the distributor, it was in and out like 4 times, I intentionally moved what gear it meshed in because it did seem like it was 'one tooth off', however the correction was only because I couldn't turn the distributor body far enough because of the vacuum can. However, now, with the edelbrock on, knowing it was good on the blazer, what now?

Snowy Rivers said:
Does the thing have the EGR valve on it ??

If so make sure that its not leaking, as in remove it and install a blockoff or a new valve.

A leaking EGR valve will make the engine run like crap especially at idle.

Just a thought

Snowy
Click to expand...
EGR is gone, now has a Edelbrock 2101 non-EGR intake that I scored for free. That was originally one of the leaks.
 
compression check

did it run good at all? If it did, what happened just before it ran like crap? What was changed?

I'm sure you went over this already in the other thread, but I seems like we're starting new again.
 
A long time ago I had a truck that idled horribly but ran pretty good. I pulled off the valve covers to see what was going on. Started it up and noticed that some of the valves were not even moving up and down. The cam shaft was perfectly round, the lobes had worn down completely. I put in a new camshaft and it was like a whole new engine!
 
Jessie James said:
A long time ago I had a truck that idled horribly but ran pretty good. I pulled off the valve covers to see what was going on. Started it up and noticed that some of the valves were not even moving up and down. The cam shaft was perfectly round, the lobes had worn down completely. I put in a new camshaft and it was like a whole new engine!
Click to expand...

Crank and valves, two things I didn't want it to be.
 
mrschaeferpants said:
Crank and valves, two things I didn't want it to be.
Click to expand...
ur in luck
Jessie says it's ur CAM. :waytogo:
it wouldn't be a bad idea to check the rockers.
that should all be found out by a compression check though first. Then you get to find out WHY the readings are as such :doah::haha:
 
You say it's a crate engine...

Could the timing mark be way off - like 90 degrees? There are different dampers for use with different timing tabs. It's easy to mix and match during a swap. Instead of fixing mine, I found TDC with the oil pan off and applied timing tape - it's like $5 from Summit and you no longer need an adjustable advance timing light.
 
I have almost the exact same setup in my truck and had a similar issue. But mine started afetr a particularly bumpy off road excursion. Ended up being the manifold fitting that is behind the carb was loose. Replaced that and was fine.
 
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