Mechanics

INCONSISTENT CURB IDLE AND LOW POWER AT HI RPMS

1985 Jeep CJ7 • 14,000 miles

OK, first, I am thrilled to be asking this question at this forum because I have dreamed of owning a CJ since I was 16. Bought my first CJ7 a week ago and have already had a blast playing with her. However, I think I'm outside my skill zone because I just can't seem to get her running well. When I bought her, she wouldn't curb idle at all and would stall every time I came to a stop. I pulled the carb off (stock Carter BBD) and rebuilt it. Set the floats/accl. Pump/choke etc. To the specified dimensions. Mixture screws are about a turn and a half out. Replaced the plugs and set the timing.

What keeps happening is that I will set my curb idle (about 800RPM) and then take her out for a spin, and all of a sudden it's idling back up around 1200RPM. I pop the hood and the fast idle cam is not engaged but the idle is way high. So I turn down the curb idle to around 800RPM again, and then after a little driving, she'll stall at stop lights. When the idle is high, she diesels a bit when I stop. When the idle is low, no dieseling but the exhaust smells rich. Actually, she always smells like gasoline which probably means I have a leak somewhere, but one problem at a time. When the idle is low, I get pretty decent power throughout all RPMs. When the idle is high, my high RPM (3000 or so) power is not so good. Also I'm burning through gas like crazy. Might be the leak (don't worry, I park her outside).

OK last thing. When I was setting the timing yesterday, I noticed that the inductive light wouldn't flash at a consistent rate all the time. It would pause which actually coincided with the engine chug/struggle. I've ordered a new distributor cap, cables, and rotor and will install them this afternoon. I've never set a dwell angle before, but could that be the problem? When I go into the distributor I'll check and make sure the rotor shaft isn't loose. Thanks for any feedback.
Avatar
Hang em hi
June 19, 2012.



Does this carb have an idle stop solenoid on the carb?


Racefan966
Jun 19, 2012.
I believe so, yes. That's the round plastic thing with a plunger on one end and a locknut on the other that has a vacuum hose and an electrical connect, right? Where the plunger meets the solenoid, the rubber is completely destroyed and it disconnects completely from the solenoid body, so I just backed the screw off so it wouldn't contact the solenoid at all. I'll post a picture when I get home. The only thing stopping the throttle from completely closing are the fast cam idle screw and the curb idle screw (or stop screw maybe?).


Tiny
Hang em hi
Jun 19, 2012.
Is there one on the carb that is electric?


Racefan966
Jun 19, 2012.
MAYBE YOUR HIGH IDLE STEPS ARE ENGAGED?

IS THE CHOKE PARTIALLY CLOSED. EVEN A TEENY IT?

DO YOU KNOW HOW TO TUNE YOUR RIG?

DO YOU HAVE TOOLS?

A MANUAL?

HAVE YOU READ SOME OF MY STUFF?

LET'S HEAR A NOVEL ABOUT YOUR JEEP/ INTENTIONS. MAYBE THIS WILL BE THE MOST YOU'LL GET TO WRITE.I GENERALLY WRITE THE NOVELS, YOUR END THROWS IN A SENTENCE OR TWO, AS WE GO. THAT'S OK, I LIKE FIXIN' CJs!

DO YOU LOVE YOUR JEEP?

THE MEDIC


Tiny
CJ MEDEVAC
Jun 20, 2012.
DIS-REGARD MY PIC ABOVE, I JUST RE-READ YOUR POST (WAS IN A HURRY WITH WIFEY, 1ST TIME)

I DON'T KNOW YOUR EMISSIONS RULES IN YOUR AREA

I SUSPECT THE OLE STEPPER MOTOR BBD CARB JUST AIN'T WORKING LIKE IT DID WHEN IT WAS NEW.......YOUR REBUILD MAYBE "PERFECT", BUT THE REST OF THE CRAP THAT MADE IT WORK, IS 27 YEARS OLD, I DOUBT THE "CRAP" HAS BEEN SERVICED OR REPLACED TO KEEP IT IN TIP TOP WORKING ORDER. IT'S PROBABLY MORE OF A BURDEN, THAN A HELP.

YOUR IDLE SPEED SHOULD BE AT 680 RPMs.....HIGH IDLE DOES CAUSE DIESELING, WHEN YOU SHUT IT OFF.

YOU CANNOT PROPERLY ADJUST YOUR MIXTURE SCREWS, WITH THE IDLE WAY UP THERE....NOR CAN YOU "TIME" THE JEEP AT THAT HIGH RPM

YOU NEED NOT WORRY ABOUT "DWELL", AS THE IGNITION MODULE DOES THAT FOR YOU. ALL YOU NEED TO DO IS "PROPERLY TIME IT".....IDLE SPEED CLOSE TO CORRECT, AND VACUUM ADVANCE LINE PLUGGED OFF WHILE DOING THE PROCEDURE.

I CANNOT STRESS GETTING THE IDLE SPEED CORRECT ENOUGH...OTHERWISE THE TIMING WILL BE OFF.

YOU NEED TO GET RID OF ANY VACUUM LEAKS.....OPEN PORTS/ BROKEN, OPEN, HOSES/ CARB MOUNTING/ LEAKING VACUUM OPERATED GIZMOS/ AND INTAKE MANIFOLD TO THE HEAD

IT TAKES ONLY TWO VACUUM LINES TO RUN THE ENGINE---"PCV" AND "VACUUM ADVANCE"..........IF YOU HAVE POWER BRAKES OR AUTOMATIC TRANNY, YOU NEED TWO MORE.

IF YOU DO HAVE VACUUM LEAK(S)---THIS IS SORTA WHAT IS HAPPENING:

YOUR CARB/ ENGINE IS GETTING TOO MUCH AIR (YOUR CARB IS DESIGNED FOR USING A SPECIFIC AMOUNT OF AIR)

WITH MORE AIR, YOU MUST ADJUST TO GIVE IT MORE FUEL

WITH AN "AWKWARD" AIR FUEL MIX, WHEN YOU OPEN UP THE THROTTLE, THE THROTTLE PLATES SORTA "EXPONENTIALLY" THROWS THE ENTIRE AIR/ FUEL MIX EVEN MORE OUTTA WHACK......YOU MAY MAKE IT RUN DECENT AT LOW SPEEDS....OR YOU MIGHT MAKE IT RUN DECENT AT HIGHER SPEEDS.....BUT YOU PROBABLY WON'T GET IT "FLUENTLY"/"EFFICIENTLY" DOING BOTH

LOOK AT May 13, 2012, AT THIS POST----SAME YEAR AS YOURS

http://www.2carpros.com/questions/1982-jeep-cj7-ignition-problem-spark-distributor-cap

WHAT YEAR/ ENGINE/ CONDITION UNDER THE HOOD?

SEND A PIC(S), SO WE GET A FEEL OF WHAT WE'RE WORKIN' ON

THE MEDIC


Tiny
CJ MEDEVAC
Jun 20, 2012.
WONDERFUL! I was hoping you'd respond, Medic, since I have been reading quite a few of your reviews. That's why I posted on this forum instead of another one. I have lots of problems with my Jeep so you'll see plenty of posts from me over the next few weeks/months/years. Would love to work with you to get my rig running as best as possible.

To answer one of your questions.I LOVE MY JEEP. She is my baby. I've been waiting a long time to take care of her, and am willing to take all the time (and hopefully not too much money) to make sure she runs as well as I can possibly make her run. I played with '84 and '83 CJ7s all through high school. Did some minor repairs, but never could call one my own. Now I can. I am an engineer so I have a slight mechanical disposition, but I have little experience doing high end engine work.

Basic CJ specs. In line 6 cyl. 258. 4 speed. Before I bought her, most was stock. I'm the third owner. The second owner replaced the oil filter and that's about it. The one before did a decent job keeping up with basic necessities such as oil, hoses, lubricants, etc. Things are pretty gunked up under the hood. Lots of grease covering most everything. Standard 1985 wear. Tubs rusted, some surface rust on frame. That sort of thing. So I know I have my work cut out for me. Which is actually exactly the way I want it.

OK here's my new update. This is definitely an air/fuel mixture issue. This is how I know. At normal operating engine temps, I noticed my choke plate was still pretty closed. I pulled off the carb again and adjusted the cover for the electronic choke to lean up the mix a bit, and now at normal operating temperatures the choke is close to wide open. However this made things worse. I have terrible power at higher RPMs but the good news is my idle is at a nice smooth 700RPM. Again, I'm eating through fuel which is no good. The new distributor cap did make a difference. The old one had some pretty bad corrosion.

Quick side note, I found a source of a gas leak. The hose to my liquid check valve on the back fender was completely disconnected and open. The connect port to the valve was broken, but I did my best to find a hose that could clamp down on what was left of it. I'll have to find another lvalve at a junkyard to ensure a good tight fit.

The engine emissions in NC are pretty tight I'm afraid, so I'm going to have to do my best to make sure things aren't too dirty out of the exhaust. But we have a full year to get everything in working order to pass inspection.

So here's my current situation, to sum things up. Tight choke - good engine power, bad idle. Loose choke - good idle, bad engine power. I'll try and adjust the electronic choke to find a nice halfway point. In the meantime, you might be right about a vacuum leak. What's the best way to go hunting for one? I'll adjust the electronic choke cover once more and retime again. I'll make sure I can get a good idle before retiming though. Glad you highlighted that.

Should I just buy a new carburetor? I can. Sort of afford it. Thanks for the feedback. Looking forward to getting her working well.


Tiny
Hang em hi
Jun 20, 2012.
Here are some picks. One of which is the solenoid plactic-thingy that I think racefan was talking about. Where would the idlestop solenoid be? Also, there looks like some kind of aftermarket mechanical choke was installed, but I have no idea if it's connected to anything or not.


Tiny
Hang em hi
Jun 20, 2012.
I GOTTA GO TO WORK SOON, SO I'LL JUST ADD A LITTLE FOR NOW

1ST PIC---CARB BOWL VENTS

2ND PIC---WHAT IS THE WHITE DEALEE W/SWITCH?

3RD PIC---THIS IS THE SOLENOID RACEFAN SPOKE OF. USUALLY AT THIS AGE AND MODIFICATIONS. THEY DO NOT EVEN WORK ANYMORE

WHAT DO THEY CHECK/ HOW DO THEY CHECK, AS FAR AS YOUR EMISSIONS?

ARE YOU "GRANDFATHERED IN" BECAUSE OF AGE. IF SO, WHAT DO THEY "LET BY"?

STILL NO PIC OF JEEP?

YOU ARE ONLY A "BORDER" NORTH OF ME

I WANTED TO KNOW WHETHER YOU WERE SPEAKING OF THE "CHOKE PLATE" BEING CLOSED, OR ARE YOU SPEAKING OF THE "THROTTLE PLATES"?

EVER THINK ABOUT A MANUAL CHOKE?

IF YOU HAVE A LOW IDLE, THEN A HIGH IDLE OCCURS, SEVERAL THINGS COULD CAUSE THIS, COMMON ONES ARE: STICKING LINKAGE (IF YOU CAN PHYSICALLY, NOW THE THROTTLE SHAFT, AND IT IDLES DOWN, THIS COULD BE THE PROBLEM)----WEAK RETURN SPRING---HIGH IDLE CAM---SOLENOID WON'T BACK OFF---THROTTLE PLATES/ SHAFT BENT, THROTTLE PLATES TO NOT "SEAL" EVENLY (ONE OPENED MORE THAN THE OTHER, EVEN SLIGHTLY)

ANOTHER PROBLEM WITH MIX SCREWS IS THAT "JOE IDIOT" SOMEWHERE IN THE PAST, TIGHTENED THEM SO TIGHT THAT HE RUINED THE SEATS. ACCURATE ADJUSTMENT WILL BE ALMOST IMPOSSIBLE NOW.

WILL SEND YOU A MESSAGE SOON. CLICK ON YOUR NAME TOP OF MOST ANY PAGE, LOOK TO THE LEFT FOR MESSAGES

BEFORE YOU GO SPENDING $$$, LET ME ASSIST YOU ON A POSSIBLE WAY TO SAVE!

THE MEDIC


Tiny
CJ MEDEVAC
Jun 20, 2012.
OH YEAH, GIVE ME A RUN DOWN ON THE SYSTEMS YOU HAVE, ANY MODS

THE MEDIC


Tiny
CJ MEDEVAC
Jun 20, 2012.
OK good news. It doesn't look like my vehicle has to pass an emissions test, only a safety inspection (headlights, wipers, turn signals, etc, which by the way it would fail). So we can rip off as much as you'd like from the carburetor.

I was talking about the choke plates earlier, not the throttle plates. And yes, I have thought about a mechanical choke. Actually, I think that white switch thingy in pic 2 above may have been an attempt to install a mechanical choke. I don't think the throttle plates stick because every time I pop the hood to take a look at why the heck it's idling so high, the idle screw is firmly on the stop. The fast idle cam screw isn't engaged either. The the throttle return springs feel pretty tight. The throttle plates might not be sealing evenly. When I rebuilt it, I did notice some sort of dried black resin stuff on the edges of the throttle blades as well as the barrels.

As far as the mixture screws. Well. I think Joe Shmoe may have done a number on them. I don't have any limiter caps. They're gone. Also when I was reading about carb tuning, this "full rich stop" kept coming up. I don't have a full rich stop. If I keep backing off the mixture screws, they pop right out. Another thing that might be a problem is when I tighten the mixture screws all the way in, the car still runs. Granted, that's only for a fast idle, but still might be a problem.

She's dieseling really bad now. I have to pop the clutch or she'll literally just keep chugging. I let it go for a full minute just to see how long she'd keep going.

As far as systems. Not entirely sure what you mean, so I'll just go through everything. 3 speed dana 300 transfer case. 4 speed tranny with reverse. AMC 20 (or 30 I can't remember) rear axle which needs a lot of work. Dana 30-or-something front. Locking front hubs. In line 6 L head AMC 258 ci engine. Some nice bookshelf speakers lying in the back which were a nice surprise after I bought her. Headlights used to work 50% of the time. Now they don't work at all. No blinker lever, but I have a new one I haven't installed just yet. Floor dimmer switch for headlights doesn't work (probably why the headlights don't work either). I have an aftermarket tach that I haven't installed yet (it's easier to use for timing than the multimeter so I've put it off). Voltmeter and oil pressure gauges appear to work ok. None of the temperature amenities work (heat, AC, vent, etc.). Looks like she has a new radiator. Maybe a new catalytic converter? It just looks kind of shiny which is rare for things underneath jeeps. New fuel filter. New-ish air filter. Everything looks stock besides the mystery switch under the steering wheel. So literally no mods (except for the uninstalled tach).

I'll play with her some more at some point today. Let me know what I should try.


Tiny
Hang em hi
Jun 20, 2012.
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