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Different idle every stoplight

Different idle every stoplight

Ogletr56b

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Location
UT
Vehicle(s)
Cj5
Completely stock down to the emission controls
1983 Jeep CJ5
6 cyl AMC 258 i6 / 4.2l

Carb: NAPA Carter BBD (California edition?) I rebuilt this last week. Made all adjustments per spec. Removed Dashpot, and plugged line.

Milage: Unknown but PO says 113k speedo is correct. As of now, nothing to insinuate otherwise. Has not been driven much in the last 10 years.

Oil pressure: ~60psi cold, 20 warm at 700 rpm idle

Spark plugs: New champion coppers

Timing: -14 ( I'm at 4,000ft) High altitude jumper is connected.

Vacuum pressure: Consistant on gauge. No leaks - verified with starter fluid. Checked all lines by diagram. Replaced warn lines with new.

O2 sensor: new


Symptoms: Always Steady idle. Problem: the idle changes every stoplight. I will set the idle to 750. It idles absolutely fine. Go for a drive, stop at the first stoplight, the idle will be at 1,100. Second stoplight 800. Third stop light 1500. Funny thing, I tap the gas at the stoplight while in nuetral, it goes from 1500 back down to 800.

I have the electric choke, I have disconnected the wires to it. Is there any way the choke can be still affecting the functioning?

Could the stepper motor on the back of the Carter BBD change the idle speed?

Thank you,
Chris
 
The stepper motor controls fuel mixture. Using the Sprynet website that Lumpy sent on your last post can really help you out here.
 
Are BOTH idle mix screws turned out the EXACTLY, the same amount?
Check ALL of the manifold bolts to be sure they are very 'tite'?
Do you have a Sol-Vac on this carb? If so, ck it's adjustment.
http://home.sprynet.com/~dale02/list.htm
LG
 
Last edited:
Ok, I have gone through the Spynet stuff again. My choke seems to be either not functioning or functioning erratically. When cold, before the ignition is turned on, the choke plate does NOT snap back. In fact adjusting the round three screwed heating element to do richness or leaness appears to do nothing.

I'm going to check voltages today, but before I do can someone look at the pictures below and do visual check to see if everything looks right. Other than adjustments (which we ALL wrong by NAPA). I reassembled the carb exactly as I took it apart. I fear that maybe a switch or something was put on backwards from NAPA.

Does the metal switch look correct for the Wide open throttle switch? Does everything else look correct on the carb regarding choke?

Also, I thought I broke the dashpot, but in fact it was the sol vac. This is what I took off and plugged the vac line. Is it vital that is is replaced, or can I keep it plugged?
 
Sol-Vac is needed IMO. It's a big part of controlling the idle speed when the engine is under load.
When you turned the choke adjustment dial full swing. Are you saying you saw no movement of the choke itself??:confused:
I'm not seeing any pictures you may have put up.
LG
 
Sol-Vac is needed IMO. It's a big part of controlling the idle speed when the engine is under load.
When you turned the choke adjustment dial full swing. Are you saying you saw no movement of the choke itself??:confused:
I'm not seeing any pictures you may have put up.
LG

Third picture down, the circle with 2 red wires - after loosening up the screws and turning it, I see very little difference in the choke plate. I don't know if this is normal. The only real movement in the choke plate is if I move it manually; even then, there is not much resistance.

Lumpy, I really appreciate all your help from the beginning!
 
WOT looks 'rite'. Unless you have A/C or all the smog stuff running. It's not a big deal. When you open the throttle all the way up. Is the switch getting contact from the linkage?
Is the choke from you other carb? I ask as it's real easy to miss the engagement pin inside the heater coil housing(black cover)and then the choke has a mind of it's own......
Confirm that you have the fuel filter return line at 12 o'clock position.
LG
 
My $.02 would be that the choke should be somewhat or at least fully closed when you have a cold engine, along with the fast idle cam up a notch or two. There is a spring inside that black covered choke adjustment that could be shot or not adjusted correctly. When you start disconnecting wires, hoses, and components it can affect computer operation. There is a lot written on the Carter BBD online and in the factory repair manual which could help you understand that beast a little better. When you first turn the key on the stepper motor will set itself and you can watch it by looking down the throat of the carb, this will indicate that the computer is functioning.
 
Wow that reminds me of the problems I had with my jeep a long time ago. Ran pretty good for the first several years then started having problems with the carburetor. Idle was all over the map. Finally got my good buddy to check it out. Master Mechanic. Think it was a carter also. Spent some time with it several times thinking he had tamed it each time. Each time it would go back to ruff or up and down idle. Finally read about weber making one for the jeep. I had had one on a bored out 1865 cc VW and had worked well. Best thing I ever did for my jeep. Never looked back and has been running well since with an additional 150K miles since
 
I think I found the problem with the different RPM at every light. The PO put the wrong throttle return spring on. It was slightly, I mean only VERY Slightly too long. I remember thinking to my self " man, they put great paint on those from factory!" When you would tap the throttle, the spring would gain momentum and snap back. I also think the spring retained more kinetic energy when it was cold. I mean, it was only slightly ... slightly too big. My wife suggested that I call the PO and ask him for a list of things he's touched... it's sounding more compelling every time I walk out to the truck.

The choke is still messed up, but at least that makes sense to me. Thank you. I couldn't think of anything else that could change the RPM.

Thank you everyone. If you would still like to continue to help me with the choke that would be great. I will follow everyone suggestions, but I'm not loosing my mind anymore!
 
If you can. Double spring the throttle return spring as a safety deal.
Good luck,
LG
 

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