83 Cj5 Running too rich

[Ogletr56b]

Completely stock down to the emission controls
1983 Jeep CJ5
6 cyl AMC 258 i6 / 4.2l
Carb: 3 months old Electronic stepper version of the Carter BBD (California edition?)
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


I'm going to start taring down the carb, does anyone know specifically where I would adjust the stepper BBD to make it leaner; for example, could I slightly reduce the clearance in the stepper valve?
This model doesn't seem to have purchasable jets.



Background information for those that choose to read it can be found below. Any suggestions are welcome.

I live at 5k ft altitude, and constantly see altitudes of 10-13kft. Consequently, I'm running extremely rich. The problem is exacerbated in the mourning when cold, presumably due to the choke being active and further restricting airflow.

Symptoms: Perfect idle. Easily starts up in 50F. Fumbles and at low speeds. Wants to shut off then will restart with motion. When coming down a steep mountain, it keeps shutting off and coming back on. I smell gas, gets 6mpg and has no power.

I have the timing set at +16, the high altitude jumper connected, spark gap set at .035, Idle mixture screws set at highest idle @ 700rpm, ran Marvel Mystery through the carb, and new air filter. It still ran poorly. In order to reduce the likely-hood of a vacuum issue I then capped the carbs EGR, and both Manifold Vac. I then bought new line for the line from carb to Distributor.

At this point, I'm thinkin' the computer can't can't compensate for stoichiometric coefficients of 10k ft for long duration, but it still doesn't account for the over rich at more moderate altitudes (5k).

Could it be the Charcoal Canister?
Could it be a spark problem? I was thinking of doing TeamRush mod, but I don't want to do it if it wont help.

The point is I'm running way too rich, and I need to rectify the problem, or my Jeep will continue to be undrivable.

Thank you,
Chris

​

 

[Torxhead]

One item that can set your engine to run rich would be the oxygen sensor. If this unit located on your exhaust manifold goes bad it can result in those symptoms. It should put out between .1 and .9 volts on a digital voltmeter and will vary as the system is in operation. This controls the fuel richness.

 

[Lumpy Grits]

I would check the float level and the choke setting.
Also-Take a wrench to EVRYDANGBOLT on the intake and exhaust manifold.
Good info here-
Table of Contents

T'head has a very good point about the O2 sensor. I have had several fail over the last 31+ years, and carry a spare in my Jeep's tool box.

Did you get a FSM yet? That will also answer allot of questions.
Can you post pictures of your engine bay so 'we' can see if there's an issue with 'pluming' and such??
LG

 

[Hedgehog]

Unplug the PCV, the engine definitely needs that to work properly, elevation shouldn't have be a problem with that system. The engine needs to breath. In another thread someone talked about hooking up a high altitude wire that is in the wiring loom. Evidently the wire goes to ground when needed.

Looking back, as I suspected it was in your thread on more or less the very same subject. That makes answering a little confusing.

 

[Ogletr56b]

One item that can set your engine to run rich would be the oxygen sensor. If this unit located on your exhaust manifold goes bad it can result in those symptoms. It should put out between .1 and .9 volts on a digital voltmeter and will vary as the system is in operation. This controls the fuel richness.

With the sensor attached to the car, I get up to .5v; at this point my car is heated up to my normal temperature which according to the cabin gauge is about 1/8 into the green above the C. I would say the normal is around .3v. I cleaned the single wire attachment with sand paper and hooked it back up. I would have to say a little more fuel was coming out of the gas pipe than before, maybe?

 

[Ogletr56b]

Unplug the PCV, the engine definitely needs that to work properly, elevation shouldn't have be a problem with that system. The engine needs to breath. In another thread someone talked about hooking up a high altitude wire that is in the wiring loom. Evidently the wire goes to ground when needed.

Looking back, as I suspected it was in your thread on more or less the very same subject. That makes answering a little confusing.

From what I remember, there is supposed to be about 50 to 100 rpm drop when the valve is not attached. Plugging my hole with my thumb and my wife in the seat, she "thinks" there was a slight drop; however, with my cabin Tach, it is hard to be sure. Is there another definitive test to indicate the prognosis of the valve?

 

[Ogletr56b]

An update, I have hooked the vac gauge up to a line and found the needle to be stable. It reads -17Hg. I'm at ~4500 ft, so this is a little high based off my calculations, but doesn't appear to be the source of my problems. What do you all think? Based off this reading and the stability of the needle, there doesn't appear to be a vac leak, valve problems, etc.

 

[Torxhead]

Using the link Lumpy put in post #3, there is a section for the oxygen sensor for a better explanation and how to test it as the voltage in your test seems a bit weak. Along with more info on how the computer works the Jeep CJ. Plus the Altitude Jumper Wire that you were interested in earlier.

 

[mtnwhlr]

I got a rebuilt carb from a local parts store and it was also running real rich and what I found was the metering rods were sticking.

 

[Hedgehog]

No need to get technical with a PCV valve. They aren't expensive and need occasional replacement. I suggest just doing it. Why not you haven't got much to loose.

 

[Lumpy Grits]

An update, I have hooked the vac gauge up to a line and found the needle to be stable. It reads -17Hg. I'm at ~4500 ft, so this is a little high based off my calculations, but doesn't appear to be the source of my problems. What do you all think? Based off this reading and the stability of the needle, there doesn't appear to be a vac leak, valve problems, etc.

What 'line' did you tie into?
17Hg @ 4500'(is this ASL?)does sound a bit high. Then again, it could be the gauge. Was the needle steady? I mean less the 1 point fluctuation either way.
FWIW: I' at 2700'(ASL)and my stock 31+ year old AMC 258 i6 / 4.2l , w/120K miles shows a steady 17-18Hg on my 25 yo Stewart-Warner V'gauge.
I still say to ck your float's setting.
Keep us post'd.
LG

 

[Ogletr56b]

I'm pretty sure the truck hasn't been driven for about 10 years before me...

I have fully rebuilt the carb to the following specifications: I have set the dry float to .25", the pump to .50". I also adjusted the metering rods, etc. My problems of richness seem to have subsided. No more black smoke! I did, however, break the dash pot adjustment screw, so I removed the dash pot and plugged the vacuum line.

Unfortunately, all is not well yet. My idle rpms seem to be different every time I push on the gas. I have disconnected the wire that attaches to the electric choke, the plates appear to be fully open.

I will set the idle to ~700, go for a drive, and the idle will be up to 1100 again, then Ill take off the stop light, and it will be at 1500, the next stop light 500, etc. Throttle doesn't appear to stick, and the throttle return spring strong. It was doing this prior to the carb rebuild. I feel confident that the carb was done correctly.

I have sprayed the whole engine compartment with starter fluid. I found a small leak (since fixed), but nothing that could attribute to a problem of this magnitude.

Other than the idle my wife drove the thing to work on a cold morning, she experienced no lack of power, and everything was great. Everything was great for about 2 hours of driving in town, but on her way home, it got really loud. I havn't been able to look over it completely, but I think it may be a BIG exhaust leak. OR could it have been that I reversed the vacuum lines to the emission upside and downside air valves for the exhaust? Could this be related to my idle issue, or unrelated?

I'm ready to throw a stick of dynamite in the back of this thing.

Thank you,
Chris

 

[Lumpy Grits]

Sounds like this might help--
Idle Problems

Do you have power brakes?
Disconnect the PB booster line at the carb, and plug carb fitting. Idle any different now?

LG

 

[Ogletr56b]

Sounds like this might help--
Idle Problems

Do you have power brakes?
Disconnect the PB booster line at the carb, and plug carb fitting. Idle any different now?

LG

Thank you. I'm going to read through your link later tonight. No, I don't have power brakes.

 

[Lumpy Grits]

That link is in the link that I gave you in post#3.
LG

 

[Ogletr56b]

I have read through the link again. I don't have a vacuum leak, my vap canister is operating correctly, and my carb is clean. All problems have gone away except for the idle problem.

Idle is always steady. Every time I push the gas it comes down to a different idle. Yesterday at one stoplight, it idled at 1500 rpms. If I tap the gas, it will go down to ~750.

The electric wires to the electric choke are disconnected, is there any way that the choke could still be affecting the functioning of the carb?

From the looks of the tailgate, smell and sound, and spark plugs, the air/fuel seem to be correct. Can the computer mess with the idle?

Thank you. For what it's worth, I'm following all advise no matter how big or small. As far as the PCV, I'm going to change it out today to be sure. Though, I dont think thats my problem now.

 

[Ogletr56b]

I would check the float level and the choke setting.
Also-Take a wrench to EVRYDANGBOLT on the intake and exhaust manifold.
Good info here-
Table of Contents

T'head has a very good point about the O2 sensor. I have had several fail over the last 31+ years, and carry a spare in my Jeep's tool box.

Did you get a FSM yet? That will also answer allot of questions.
Can you post pictures of your engine bay so 'we' can see if there's an issue with 'pluming' and such??
LG

I have taken a wrench to every dang bolt on the the carb and exhaust, replaced the O2.

These are what the spark plugs looked like before I changed them out. They were the new-fangled 8$ Bosch Platinum's. I changed them to Champion coppers.

 

[Ogletr56b]

 

[Ogletr56b]

I believe that this issue is somewhat unrelated to the original richness issue. I'm going to still check this thread often, but I'm going to start a new thread specific to this issue - perhaps get a little more exposure.

Thank you for everything. Chris.

 

[Torxhead]

In reference to post #16: The idle is controlled thru the computer, thru the Sole-Vac throttle positioner and there is also a vacuum solenoid that helps operate it.