high idle help!

My '86 2.8L XJ is acting all funny. It's now -20 where I live, and the heap starts and idles fine. However, once it's warmed up, it idles at around 1500 rpm. I've checked the choke to make sure it's operating correctly, and it appears to be fine. It was running well when it was warmer, so I'm not so tempted to start messing with idle and mixture adjustments. It does smell a little rich out the exhaust pipe when it's warm. I've noticed there's a plunger of sorts that forces the throttle lever to open a little. When I counteract it (only requires a light push with my finger), the rev's back off. What is it, and could it be causing my probs? Anything else I should look at to resolve this issue? All hail the mighty carb gurus! Help my machine!

From what I remember of Carbs...that is the choke pulloff plunger...My old Chevy truck had one.... the plunger was attached to a metallic coil that would contract as things warmed up, and it would pull open the choke plate in the throat of the carb to give it more air, and the motor would run less rich, more lean, and drop the idle down...newer models had one that were electrically heated and controlled...

Try cleaning it up, making sure none of your linkages are sticking, etc.

if the "plunger" thing is hooked to a electrical solenoid it is probably a fast idle device for when the A/C kicks on. do you have the defrost on, which will also turn the A/C on? if it works ok without it, then just unplug the solenoid

Question - if you start it cold and let it sit while it warms up, does the idle slowly creep up to the 1500?

Indeed it does. When I first start it, it sits at the recommended 700 rpm, and after about 10 or 15 minutes, it's found it's way to 1500 or so.

Has anyone had any success swapping the Varajet out for something a little more user friendly? I'd be pleased as punch to plonk a holley 2bbl on there...

My first bet would be - an intake/exhaust manifold leak

Here is a recent thread on the subject
http://www.naxja.org/forum/showthread.php?t=934216

Here is a another post containing a large amount of information on high idle issues.
http://www.naxja.org/forum/showthread.php?t=81838&highlight=High+idle+issues

Hope this helps ..

Sorry didn't see this statement

"When I counteract it (only requires a light push with my finger), the rev's back off.'

This should nullify an intake/manifold leak.

This sounds more like a sensor issue (TPS, etc) or an SBEC issue..

I'd say that you have a vac leak just from my nightmare of a time with my carb.

As for dropping the Rochester... I went for a Weber 2bbl. They make a nice drop on kit.

I just had the same problem with my 86 w/2.8. The solenoid that controls the throttle kicker is activated by three items. they are A/C, rear defroster, and power steering (when put to the stops). Mine was a bad power steering pressure switch. I un pluged the switch and it idles at about 800 instead of 1500. hope fully this helps.

Matt

ATON Ranger said:

The solenoid that controls the throttle kicker is activated by three items. they are A/C, rear defroster, and power steering (when put to the stops). Mine was a bad power steering pressure switch. I un pluged the switch and it idles at about 800 instead of 1500. hope fully this helps. Matt

Click to expand...

Rear defroster and power steering pump? Hmm, are you sure about this? Neither (to my knowledge) have any feedbacks to the SBEC etc. I don't know much about an 86, but that seems really odd :shocked:.

That is what the chiltons said, which at first I thought was wrong. But after I tore into the harness found four wires spliced to the solenoid. 1 was to the solenoid and the other 3 went to the previously mentioned items. I guess the rear defrost is high amp draw, the power steering and a/c can stall the engine at idle.:dunno: Then again it is a jeep.

Matt