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Unread 11-22-2006, 09:45 PM   #1
howellru
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Join Date: Apr 2006
Location: Jackson, MS
Posts: 234
MotorCraft 2100 adjustment

I recently bought an 89 YJ 4.2L with the popular motorcraft carb conversion. The set up seems simple enough, but I can't seem to get fuel flow and idle ratio right. Runs decent, not great, when cold & choke is on, but once warmed up it sputters and stalls like dickens, especially when idling and at stop sign. Have to put in neutral to prevent.

Anyone offer or know where I can find instructions on properly setting for fuel flow screws and idle? Currently, the fuel flow screws are about two full turns out from fully closed and idle in park is aobut 800 RPM.

OMT, once the engine is warmed up and I notice strong waves of fuel odor in cabin if I run windows down; especially on highway. Makes me dizzy

It's not much of a close up, but here's a pic link http://s128.photobucket.com/albums/p...rent=My4-2.jpg

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'89 YJ Wrangler, 4.2L, MC2100 Nutted Carburator
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Unread 11-22-2006, 10:11 PM   #2
volcom3375
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i also get the strong smell of fuel when driving, not to say that it's common with motorcrafts but if you ever get the fix for that well, i'd like to know too :P
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Unread 11-22-2006, 10:57 PM   #3
howellru
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Trust me, I'll be sure to pass along any solutions.
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'89 YJ Wrangler, 4.2L, MC2100 Nutted Carburator
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Unread 11-23-2006, 08:20 AM   #4
dbguync
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Try this link. This is how I tuned mine using a vacuum gauge

http://www.greatcj8.com/mc2100.htm
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87 YJ, 3.5 BDS kift, 33x12.5 ProComp MT's, 4.2, Nutter bypass, Weber carb, HEI ignition, Lockrite in the front , 8.8 in the rear, 456 gears all around. Oh, and a warn winch, etc, etc, No money left,
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Unread 11-23-2006, 08:23 AM   #5
dbguync
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Well, you have the curb idle adjusting screw on the driver's side,
the fast idle adjusting screw on the passenger side, the choke adjustment
(by spinning choke housing to give it more or less spring tension),
and the two idle adjustment screws on the bottom front.

Make sure your choke is opening, because that would make it run real rich.
Adjust the idle adjustment screws with a tach to get the highest RPM's on the lean side.
Set the curb idle for about 650 to 750 depending on your tranny.
There's a mark on the stepped cam of the fast idle linkage you line that screw up with when the choke is closed.

Kinda hard to explain in writing. Best bet would be to get a shop manual or go in Pep Boys or somewhere and "browse" a little. Remember, you'll be best looking in a Ford manual.

Find a MANIFOLD vacuum source and hook your vacuum gauge to that, If you dont have a vacuum gauge.....get one!
After the engine is warm, turn it off and find the "mixture screws" 1 per barrel underneath the fuel bowl. Turn the screws all the way in, but be gentle (you could damage them).
Then turn them out 2 full turns be sure that they are equal.

Start the engine and set the curb idle by adjusting the screw on the throttle arm.

Now adjust the 2 "mixture screws" together in or out to obtain the highest vacuum reading.
You may need to readjust the curb idle screw during this to obtain the correct rpm.
Any questions do a search on www.Jeepsunlimited.com in the CJ Tech section for mc2100 tuning

Back to GreatCJ8.com
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87 YJ, 3.5 BDS kift, 33x12.5 ProComp MT's, 4.2, Nutter bypass, Weber carb, HEI ignition, Lockrite in the front , 8.8 in the rear, 456 gears all around. Oh, and a warn winch, etc, etc, No money left,
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Unread 11-23-2006, 09:20 AM   #6
howellru
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Here are some pics of my carb. Where exactly are the fast idle and curb idle screws?

http://i128.photobucket.com/albums/p...ft_Carb_01.jpg

http://i128.photobucket.com/albums/p...ft_Carb_02.jpg

http://i128.photobucket.com/albums/p...ft_Carb_03.jpg

http://i128.photobucket.com/albums/p...ft_Carb_04.jpg
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'89 YJ Wrangler, 4.2L, MC2100 Nutted Carburator
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Unread 11-23-2006, 09:59 AM   #7
lah2420
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1995 YJ Wrangler 
 
Join Date: Mar 2006
Location: , Arkansas
Posts: 853
The curb idle screw is right under the point your accelerator rod attaches on the driver's side.
The fast idle is behind and below the choke assembly on the passenger side. It only adjusts idle when the choke is on.
The idle mixture screws are on the front of the carb right above the mounting plate.
As stated above, get a vacuum gauge and set it as outlined. Wait several seconds between each adjustment.
One thing I ran into on mine was that the EGR valve didn't have a gasket, causing a major vacuum leak that messed up setting the idle. I refuse to say what happened to the EGR valve.
Another thing I had to do was throw away the book setting the ignition timing. Set it to 8 to 10 degrees before TDC at idle. The book says to set it at 1600 rpm.
Also, if it hasn't been done, research and do the nutter bypass if possible.
Those last three things together fixed bad idle, poor fuel mileage, and rich smell on mine. It runs better now than any time since I bought it 5 years ago.
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Unread 11-23-2006, 11:12 PM   #8
howellru
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For the last week, been running idle in park @ 900 rpm, in gear @ 750 rpm. Caused occassional stalls at long red lights unless I put in neutral.

This morning, adjusted fuel mixture screws a bit and sped up idle in park to just above 1,000, idle in gear to about 900. Still sputtering, but no stalls. Now a little dieseling and overpowering fuel odor when exiting after 30 minute drive. I'm pulling my hair out trying to illiminate sputter and get smooth idle.

Also, noticed the choke plate is always wide open whether first cranked on cold morning or after driving for over an hour.

http://i128.photobucket.com/albums/p...ft_Carb_01.jpg
http://i128.photobucket.com/albums/p...ft_Carb_02.jpg
http://i128.photobucket.com/albums/p...ft_Carb_03.jpg

This is my first carb vehicle and, as you may have figured out, I don't know squat about them, but could that be part of my problem? If so, how would I correct it.

Alot of members suggested vacuum leak, but I haven't a clue how to track one down. Anyone know where I can get "Carbs Adjustment and Vacuum Leaks for Idiots" type instructions. Pictures a plus... no, a must.
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'89 YJ Wrangler, 4.2L, MC2100 Nutted Carburator
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Unread 01-30-2010, 04:17 PM   #9
anklenawer
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1991 YJ Wrangler 
 
Join Date: Dec 2009
Location: Virginia Beach
Posts: 12
did you ever figure this out - im having the same problem.
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Unread 10-26-2011, 10:34 PM   #10
cagaito
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1988 YJ Wrangler 
 
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Location: fort irwin, CA
Posts: 9
Both of ur, figured out th problem? im stock with mine and this th only thread close to mine issue.
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Unread 10-27-2011, 01:17 AM   #11
anklenawer
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1991 YJ Wrangler 
 
Join Date: Dec 2009
Location: Virginia Beach
Posts: 12
yes, i t was a while ago man - but i found out that it was the bad distributor... the guy i baught it off of said he replaced it - come to find out - he was an idiot and replaced the ROTOR.

anyway- so i spent 65 bucks or whatever and timed it with a new distributor, bang - ran/idled fine. i went crazy after that motocraft, and i think it was fine the whole time - that was a while ago - now I'm in hawaii with a 95 yj ( fuel injected) aha a loving life - but about to be in VA with a CJ if i can find one for a decent price

thanks guys - keep waving
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Unread 10-30-2011, 07:54 AM   #12
buckshot500
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1990 YJ Wrangler 
 
Join Date: Feb 2009
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Posts: 793
The fuel odor may be coming from the 90 degree connector for the rollover valve.

This valve is located inside the fender at the passenger rear corner of the tub.

There is a plastic cover panel that can be pulled down to open the void. Inside you'll see a plastic valve that looks a little like a fuel filter. There is a rubber elbow that gets dry rotted and will leak.

This elbow is available from dealers and is about $30.00, or it was a few years ago.
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Originally Posted by 5point1 View Post
Well after I drained the oil, I ran water through the engine to clean out the gunk. (the guy who owned before me obvioulsy didn't know how to maintain the engine).

90YJ98XJ
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