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Discussion Starter · #1 ·
Okay, I'm sneaking a Truck Tech question in here.

When I start the truck cold, it hits fast idle easily enough, but if it has to sit at idle for a bit it tends to load up with fuel like it is getting flooded. If I just start driving right away it is fine. This can be kind of irritating since if it does load up and then I start to drive it can kind of bog down and sometimes dies. It can't be doing much for my gas mileage either.

Can the fix be something as simple as reajusting the choke? This is a Q-Jet with the little coil spring actuator. I preset it to the proper factory specs but something's wrong. I sure wish I could fit this carb with a great electric choke I had on my old carb (no mounting boss or proper linkage on this simpler carb). How do I adjust the choke? Could I have the wrong coil spring actuator?

Also, since I run a cooler-than-normal 165 degree thermostat to keep the engine at or below 200-210, it does take a little longer than normal to warm up to the point to come off fast idle. I've never been able to get the thing to stay running at the proper idle (500-600) in Drive at a stop (it dies) but I think that is due to the new high torque towing cam more than anything. At least I hope so.

It runs great on the road warm or cold aside from the slightly higher warm idle requirements (about 800-850).

Thoughts?
 

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Its hard to point to one single thing that could be causing this. It may be a multiple of things. Adjustments to carbs usually require a set pattern to follow and adjusting one thing before adjusting another can only cause more problems. Adjusting the choke is not a easy task as it would seem.

But if it were me the first things I would replace are those vaccum pulloffs, the small plastic diaphrams. These often leak and the result is what you describe. Also there could be other carb adjustments that are out of wack. If you are trying to adjust things you may be frustated in a big way. Another problem with the choke coil on the intake manifold is that the manifold may have a heat passageway under the choke coil that heats it and if its plugged with carbon (99.9% of them are), it will not heat up the coil very fast. Removing the carbon is a tough job, have to take off manifold, remove carbon.

Sometime the only solultion if to replace the carb unless you can find a good carb man. A do-it yourself job it is not.
 

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Discussion Starter · #3 ·
Well, I'm doubtful those are my problems since the engine has a fairly fresh rebuild and the same for the carb about 4000 miles ago.

The hot air passages in the heads and manifold were cleaned out while it was appart. I rebuilt the motor and the carb myself. The carb works great with the exception of the cold idle load up. The carb contains the stock jetting and is the correct original equipment carb for this engine (a non-smog system so the carb is exceptionally simple). The single external dash pot was replaced with a new one at the time of the rebuild. I also tested the vacuum ability of the dashpot and the vacuum advance can and the vacuum accumulator on the trans at the time of the rebuild. The power brake booster is also new and does not have any vacuum leaks.

The trans has a B&M shift kit which tightened up the shifts and improved the 1-2 and 2-3 shifts a noticeable amount though I did stick with the stock torque converter.

I'm still thinking it is all in the choke adjustment and/or coil spring. Since this engine is not original to the truck I don't have a shop manual that will instruct me as to how to adjust this choke system.
 

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Rich,

See if you can open up the choke pull-off a little, there's nothing sacred about these adjustments, it's just what works for you. The manual wouldn't help much.

Does your heat riser, the butterfly in the passenger side exhaust pipe, work right? If it's stuck open the intake manifold will be slow heating up, cause this rich condition.

Tom
 

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Discussion Starter · #5 ·
Well, since it doesn't HAVE the heat riser on the passenger side pipe anymore, that could be part of the problem too! It was never there when I got the truck so I assumed it wasn't supposed to have one. Maybe something I should check into. But would that have any affect with the cold idle loading up problem?

I think I'll start by openning up the preload on the choke and hope that helps a bit.
 

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Discussion Starter · #6 ·
PROBLEM SOLVED!

The ultimate solution was so simple it ticks me off I've let it go this long without attention. I was playing around with the truck yesterday with some last minute tune ups, top offs and alike to be fully prepared for the trip. When I turned my attention to the choke, the butterfly seemed to be at a slightly open position which seems about right for cold idle. Then I noticed a huge lake of raw gas on the intake manifold! Well DUH! I've got a leak-o-jet!

A quick tightening of the carb body screws and the bolts holding it to the manifold and it all dried up. I just hope the leaks were to the outside and not to the inside. I fear this has been going on for some time now and I'd hate to think raw gas has been running down the inside of the intake, washing the oil and ruining the cylinder walls.

Anyway, it runs fine now cold or hot. I'm hoping this will also slightly improve my fuel mileage! I'll be carrying along a spare carb kit on the trip in the event I have to rebuild the damn thing on the way.

I suppose I should pull a couple of plugs to see if they are fouled from excess gas, what color would they be if I was running excessively rich?
 

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Rich, wait a bit b4 you pull plugs to give the sooty black coating time to burn off. In fact, if it does not have an HEI or CD ignition, I would just pop in a fresh set if the few you pull look black and sooty. Or wire wheel the old ones.

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Gene Chaas
Gold Member 62/ACES 3112
67 SS 427
"Be big. Be a builder."
 

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Discussion Starter · #8 ·
I do have an HEI. I have to drive the truck on Saturday for a honey-do errand so I'll check them on Sunday. Damn things are those expensive Rapid Fires so I hope they aren't fouled at all.

At least I figured this out before towing with it for a gagillion miles.....
 
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