• Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.

Jeep Rough Idle or Dies when Idling

Jeep Rough Idle or Dies when Idling
kenny 84 CJ7

kenny 84 CJ7

Jeeper
Posts
51
Thanks
0
Location
Charleston SC
Vehicle(s)
1984 CJ-7
Hello All,

Problem:
I have a 1984 Jeep CJ7 with the AMC 258 i6 / 4.2l and Carter BBD carb. Recently the jeep started to die when it came to an idle. I wouldn't say the problem came on all of a sudden, some days it would have a very rough idle but normally would get better after driving. This specific instance though it just would die every time I came to a full stop. Would run fine when driving.

My first thought was change the Ignition Control Unit with a spare I had. Previously had the ICM go bad on me and always keep an extra now. This didn't help the issue at all, so I am ruling that out.

I came across a few article that detailed a similar sounding issue and suggested cleaning the venutri assembly within the carb. I gave this a try, and it was definitely dirty in there. There is a link below to the instructions I followed when cleaning the parts.

Fix idle and stalling problems on a jeep cj-7 or wrangler yj

I put everything back together and it ran well the first two time I ran the jeep around. But then the third time I drove it the Idle started to get bad again. It would not die, but idles around 500 or so. The idle can be rough. Im worried that when I put everything back together I didnt get the throttle and choke linkage back in the correct spots. I have attached some pictures below. Maybe they will help.

All thought are appreciated.

Thanks

Eoin

IMG_20140507_163054_928.webp

IMG_20140507_163100_707.webp

IMG_20140507_163131_161.webp

IMG_20140507_163134_546.webp
 
There is an idle solenoid that could be the problem, as that is what controls idle speed. If you had a bad icm, it would have an ignition miss at all speeds.
 
Torxhead said:
There is an idle solenoid that could be the problem, as that is what controls idle speed. If you had a bad icm, it would have an ignition miss at all speeds.
Click to expand...

Thank you for the quick response. I see the idle solenoid and was wondering if I should switch it out. I see that it has a screw that touches it on the throttle linkage(not sure if thats what it is called). That screw can be adjusted. I also read somewhere that the Idle solenoid can be set to 500rpm or 900rpm. not sure if there is any truth in this.
 
There could be issues with that solenoid or its electrical and vacumn sources. Everybody with a late model CJ should have a link to this guy:Jeep Adventures Under the Hood
This could help you track it down. Look up "Sole-vac" in the table of contents as that is what it is called.
 
Torxhead said:
There could be issues with that solenoid or its electrical and vacumn sources. Everybody with a late model CJ should have a link to this guy:Jeep Adventures Under the Hood
This could help you track it down. Look up "Sole-vac" in the table of contents as that is what it is called.
Click to expand...

I have since been all over this website reading everything so far. One of the major things I have noticed so far is that my metering pins are not moving at all inside my carb. As i mentioned it seems to run fine while driving. But i go get a heavy smell of fuel. Perhaps it is running too rich.

Im going to try and check the O2 sensor. Any other thoughts?
 
The oxygen sensor could be to blame here. There is a way to test it with a digital volt meter. With engine running that sensor will put out .1 to .9 volts and it should be constantly changing as it adjusts fuel mixture. If you get a steady reading, it is shot.
 
Thanks for the advice. I will check the o2 sensor today, but I am honestly thinking of just doing the Nutter Bypass at this point. Just taking the computer out of the equation all together may help me tune this jeep back to the beach runner I need it to be.

I live in SC so we dont have any emissions testing. I believe this will take the stepper motor and o2 sensor out of the picture?
 
Doing the Nutter by-pass and a Team Rush upgrade will help only if the oem emissions system is shot, it is an old outdated complex setup and a lot can go wrong by now. I would recommend leaving the egr and pcv valve in place though, and adding a valve cover breather cap near the firewall. Most guys change out the carb since the oem one is really shot by now. I have since converted to smog legal fuel injection and it blows away the existing setup in added power and economy, but do have to deal with emissions testing which is no problem but it is $60. every two years. To completly remove the oem system including wiring, it is done in the fuel injection instruction manual for the Jeep AMC 258 i6 / 4.2l on the Howell Engine Developments web page on the net:
Support :: Installation Manuals - Howell Engine Developments, Inc.
It is always possible that your state will eventually convert to emissions testing or you might move to another state that does so be aware of that.
 
Ok, so a quick update. I did the nutter bypass and it actually got worse. I was not able to adjust the stepper motor at all. It was all frozen up.

I ended up reversing what I had done with my nutter bypass and got it running enough to bring by my local mechanic. He adjusted the carb using the front screws. It runs now but i have to say, still idles a little rough at low RPM. somewhere around 650 rpm. I was not able to ask the mechanic what he did because his wife went to the hospital, and he was not around for me to speak with.

I could live with it the way it is, but im not sure if it will it will continue to run strong. When I start it I have to pump the gas or it wont start. I have read places that that style of starting is not good for the carb. Not sure if thats true.

Now that the carb has been adjusted I might try and put the nutter back to cut out the computer, see if that helps any. Main thing i want to do though is get it idling a little better and not having to pump the gas to start.

any thoughts?
 
kenny 84 CJ7 said:
Ok, so a quick update. I did the nutter bypass and it actually got worse. I was not able to adjust the stepper motor at all. It was all frozen up.

I ended up reversing what I had done with my nutter bypass and got it running enough to bring by my local mechanic. He adjusted the carb using the front screws. It runs now but i have to say, still idles a little rough at low RPM. somewhere around 650 rpm. I was not able to ask the mechanic what he did because his wife went to the hospital, and he was not around for me to speak with.

I could live with it the way it is, but im not sure if it will it will continue to run strong. When I start it I have to pump the gas or it wont start. I have read places that that style of starting is not good for the carb. Not sure if thats true.

Now that the carb has been adjusted I might try and put the nutter back to cut out the computer, see if that helps any. Main thing i want to do though is get it idling a little better and not having to pump the gas to start.

any thoughts?
Click to expand...

I need to add that it starts right up after it has been running. But any time it has sat around, 1 day... even a few hours i have to pump the gas to start it. Fuel pump and and ignition coil are not very old. PO had replaced them.
 
The later model BBD carb equipped CJs are known for acting like that. It sounds like in your case the fuel has evaporated or leaked out and the fuel has to be pumped by the starter back into the carb to fire up. When you go to start up your rig after awhile, look down the throat of the carb and activate the throttle to see if there is any fuel coming out of the accelerator pump nozzles.
 
With a carb you have to pump it to get to start when it's cold it's just the nature of the beast.
 
Lumpy Grits said:
It's a carb, NOT, FI. You got to pump once to set the choke.
Read this.
Jeep Adventures Under the Hood
Sounds to me you had the classic clogged idle jet deal and no need to nuttered it.
Idle Problems
LG
Click to expand...

Thanks for looking at my problem, but if you read my first post youll see that I already cleaned the carb idle jets. When i put it back together it ran fine for a day, but i must have not put the throttle linkage back together right. That has since been solved more or less, still have a slightly rough idle.

As for pumping the gas to get it to start, im not talking about having to pump it once, or even twice. If its cold i have to pump the gas constantly to get it to start. even pump while it is cranking.

I have been all over jeep adventures under the hood.
 
kenny 84 CJ7 said:
Thanks for looking at my problem, but if you read my first post youll see that I already cleaned the carb idle jets. When i put it back together it ran fine for a day, but i must have not put the throttle linkage back together right. That has since been solved more or less, still have a slightly rough idle.

As for pumping the gas to get it to start, im not talking about having to pump it once, or even twice. If its cold i have to pump the gas constantly to get it to start. even pump while it is cranking.

I have been all over jeep adventures under the hood.
Click to expand...

My read'n comp skillz are just fine.:chug:
You knocked more crud loose and plugged the idle jets again. This is VERY COMMON-Do the idle tube mod!
Also sounds like your float is set to low and/or the accelerator pump is bad.
Is the return line(smaller size)on you f'filter at the 12 o'clock position? It must be.
AND-Are BOTH idle mix screws tuned out the EXACT same??
LG
 
You must log in or register to reply here.

Jeep-CJ Donation Drive

Help support Jeep-CJ.com by making a contribution.

Help support Jeep-CJ.com by making a contribution.
Goal
$200.00
Earned
$0.00
This donation drive ends in
0 hours, 0 minutes, 0 seconds
  0.0%
Contribute
Back
Top Bottom