Acceleration issues - JeepForum.com

 
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post #1 of 8 Old 06-18-2015, 11:53 AM Thread Starter
memoon
Registered User
1989 YJ Wrangler 
 
Join Date: Mar 2014
Location: lexington
Posts: 180
Acceleration issues

I'm stumped on this one and frustrated. 89 Wrangler, 4.2, 5 speed (ax15).

Jeep will crank. Jeep will idle. Jeep will rev. No missing, no idling issues, just sits and runs like a champ.

I get on the road and get into the gas, the Jeep starts bucking/chugging like it isn't getting gas. If I stay in it long enough, it will cut itself off from the chugging.

Things I've done:
-Plugs - Champion Copper
-Wires
-Rotor
-Distributor Cap
-Fuel Filter
-Fuel Pump

Carb appears clean, but I have not taken it apart for a rebuild yet.

The exhaust leaks from under the Jeep. No evidence of the manifold being cracked or damaged, but I haven't removed it for closer inspection.

Nothing funny with wiring that I can think of....only auxiliary items are a winch and a set of spot lights.

My next step was to remove the carb and rebuild/clean it. I'm still not convinced the problem doesn't exist in the gas tank.

Any help or guidance would be much appreciated. I'm trying to avoid taking it to the mechanic. As good as he is, I'd rather do it myself and 1) save the money and 2) have the sense of accomplishment.

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post #2 of 8 Old 06-18-2015, 12:01 PM
Jeepsr4me
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Join Date: Dec 2004
Posts: 8,831
only 3 things I can think of... Trash in tank, and trash in the carb.... and a timing issue with the dist..
more to do with the springs and weights and vacuum advance

I have a little inline electric pump, I would install it right before the carb and route a line into a clear 1 gallon jug..
Then turn it on... It will not take long to see if its pulling trash in the line...

Next would be a rebuild of carb, its NOT HARD so dont be scared..... get a kit but taking the number off the tag on top of carb to the parts store and get a kit...
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post #3 of 8 Old 06-18-2015, 01:02 PM
Que89YJ
Web Wheeler
1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit
Posts: 21,932
Memoon. Is NC a emissions test state? Have you done the Nutter bypass? They are issues that you would never see on a carb, float, needle valve, etc., that can cause issues. Are you using a stock carb? MC2100
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post #4 of 8 Old 06-18-2015, 02:32 PM
Mike Romain
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1986 CJ7 
 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant
Posts: 18,089
I have had similar issues when I plug up the air filter on the gas tank vent when out mud bogging. The test is to crack open the gas cap and see if it runs right.
The filter runs about $2.00 and is on the bottom of the charcoal canister. First one is a bear to change, its glued in, after that they just tuck in.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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post #5 of 8 Old 06-18-2015, 04:26 PM
ZR90YJ
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1990 YJ Wrangler 
 
Join Date: May 2015
Location: Brentwood
Posts: 921
Garage
Quote:
Originally Posted by Jeepsr4me
only 3 things I can think of... Trash in tank, and trash in the carb.... and a timing issue with the dist.. more to do with the springs and weights and vacuum advance I have a little inline electric pump, I would install it right before the carb and route a line into a clear 1 gallon jug.. Then turn it on... It will not take long to see if its pulling trash in the line... Next would be a rebuild of carb, its NOT HARD so dont be scared..... get a kit but taking the number off the tag on top of carb to the parts store and get a kit...
also the accelerator pump on the right side (looks like an awkward circle thing with a flimsy metal rubber thing in it that moves back and forth, wanted to describe it for OP) but my brother has a 90 and he had the same issue, we found out his accelerator pump was going out so we just nutter bypassed it and got a new carb with hei distributor (hei will make life easier)

just listen to me right meow, bunty's soap is here
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post #6 of 8 Old 06-19-2015, 07:58 PM
calpbs
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1992 YJ Wrangler 
 
Join Date: Jul 2009
Location: Ringgold
Posts: 698
My 94 jeep had a similar issue and it was a pinched return fuel line. I suggest you look for blockage that may cause vapor locking.

I have done so much with so little for so long, I can do anything with nothing forever.

Charlie Lamar
Ringgold, GA
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post #7 of 8 Old 06-29-2015, 06:43 PM
atmu5fear
Registered User
1987 YJ Wrangler 
 
Join Date: May 2015
Location: Orangeville
Posts: 29
My 87 yj 4.2 did this constantly for the first few days after i bought it, PO told me it had carb issues. The electric choke pull off wasn't getting 12v from the oil temp switch and therefore not coming off fully. Fed it 12v, and it would accelerate fine. Cleaned venturi assembly, nuttered it, set the timing to 8 btdc, and manually tuned the carb. Runs like a top now, would never know she's got 280,000 k and running a stock carter. Not saying yours is a choke issue, but sometimes it's the simple things we over look, worth checking.
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post #8 of 8 Old 07-06-2015, 06:21 PM Thread Starter
memoon
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1989 YJ Wrangler 
 
Join Date: Mar 2014
Location: lexington
Posts: 180
To everyone that offered advice: thank you!
I've been pretty busy with work, so not much time to play on the forums.

Things I ended up doing to fix:
Dropped tank and cleaned out the sludge and junk.
Cleaned sending unit/sock
Blew out fuel lines
Cleaned carb 3 times
Plugged the return line and bypassed it entirely
Put 93 octane in it.

Driving much better. It was primarily junk in the tank and a semi-clogged carb/fuel lines.
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