Rough idle question.

[billh1963]

After apparently solving my vibration problem by installing new shocks, I have one more issue to resolve before the truck is good to go.

The truck is a 1985 D100 with the slant six and an automatic (no air). The problem is that the truck idles very rough when in gear and I am stopped. When the truck is in park it idles okay (barely okay...not as smooth as my 2003 Hemi Quad cab, but acceptable). When the I put the the truck in gear the idle is terrible and feels like it is ready to cut out. Once I'm on the road it seems to run fine. I have changed the plugs, PCV, etc. Could it be the carb or am I missing something?

The truck is all original so it has the factory carb, smog equipment, etc.

Thanks!

[GHS]

Have you checked the PCV line? Single barrel Slants have a tendency to plug the passage where the PCV line attaches to the carb. Because of the right angle, it plugs easily and is very hard to clean out.

[billh1963]

No, I didn't. I'll check tonight. Thanks!

Are slant sixes usually very smooth idling? My past experiences with Fords and Chevy's have been that straight sixes are very smooth.

[billh1963]

Checked the PCV hose and it was clean. I also made sure that the spark plug wires were seated good. The Bosch Platinum tip plugs I put in seemed to help but it's still not as good as I would like.

I let the truck idle for a long time and then shut it down. It dieseled a little bit on me and blew off the PCV hose! Knowing that dieseling isn't normal, could that be symptomatic of the idling problem? What causes dieseling?

Thanks!

[Speed Dragon]

Sounds like the carb may need building. Dieseling usually indicates a rich condition.

I wouldn't run platinum plugs in it, I always run either Autolite or Champion. Platinums are junk in a carbed vehicle IMO. Especially one that's not running properly.

Have you tried to set the idle mixture and speed yet?

[billh1963]

I set the idle speed per the book. I'm good at some things mechanically and others I'm not. A carb rebuild is not something I have not been successful at in the past.

Could I buy a new carburettor that is "ready to go" or is that even an option?

[Speed Dragon]

Yeah you can buy them. Usually they are pretty close to being right, although you may have to adjust the idle mixture some still.

Have you checked for vacuum leaks? Intake leaks?

[billh1963]

No I haven't. What's the best way to check for these?

Also, If I do need a new carb who is the best source?

Thank you for the help.

[bherder]

If you decide you need a carb, check out:

partsamerica-dot-com (Hmmm... They still won't let me post a link)

(Shuck's - Kragen - Checkers .... depending on what part of the country you live in)

I've bought two rebuilds from them over the net (They carry items that you can't buy in stores) .... One for my 79' Powerwagon and one for my 83' Bronco. Both have been excellent and $75-100 cheaper than over-the-counter prices at, say, NAPA.

So far as the rough idle, have you made sure your cap-rotor-wires are in tip-top shape? My powerwagon was giving me fits once and it turned out to be a bad plug wire, even though they were only about a year old.

Dieseling might also be timing... As in too far advanced....

If you've got the time, you also might want to do a compression check. That can tell you a lot....

Good luck!

[Chump]

Cap, rotor, wires in good shape? Does your truck have the ESA ignition? If it does there is a black box under the hood on one of the fenders? Make sure the tranny fluid is at the correct level also.