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Old 01-04-2010, 10:56 PM   #31
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did you ever adj your timing? I would check that.
I will have to second what's been said about the weber, that's what I have on my 87 and it reminds me of my solex carb I had on my Opel back in the '70's. Always adj it.
Now that it's single digits here and below zero in the mornings I'm sure I'll have to do some adj. on mine. That is after I'm done replacing my trackbar bushings and trying to repair my gas tank leak
Thanks for your service!

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Old 01-04-2010, 11:12 PM   #32
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I would bet the problem is the accelerator pump in the carb.

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Old 01-05-2010, 02:11 AM   #33
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ok ok ok ok ok

just got off the phone with my buddy who was in japan for a while - the one who was helping me time it - appearently he noticed and either i forgot or he didnt' mention -

that there was play between crankshaft and somthing else - indicating a loose, or skipped tooth on my timing chain - somthing like that -

he said if a cleaning of the carb doesnt do it - its probably that timing chain - he said there was a lot of play in it and makes sense that after a warm up - the chain would get looser and looser - and uphill would make it almost impossible and cause it to be off in timing - which is what seems to be happening here -

so - before i order the parts - i am going to check with the local napas around here - and see what they got for me - but it should be it man - i sure hope so..

thanks for all the help - will post results obvoiusly - !!

scott - i'm nervous if this doesn't work man - i might give up and shop it!!! i need your hope! haha

later guys
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Old 01-05-2010, 02:00 PM   #34
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Hey Kyle ,
Replacing the timing chain and gears is a pretty simple job so don't worry and if your buddy knows that it has skipped timing . DO NOT RUN IT until you fix it. It can trash a lot more stuff if it skips more or breaks the chain.

scott
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Old 01-05-2010, 03:48 PM   #35
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yeah hes right u can wreck the whole valve train
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Old 01-05-2010, 05:08 PM   #36
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Thank goodness I found this thread!
I've been having very similar issues with my 89 4.2. I upgraded to the MC2100. It was running so rough that I would go through a whole tank in less than an hour. I took it to the carb shop here to have the guys look at it and see what I did wrong in adjusting it and they seemed to have gotten it fixed pretty well. They told me the Brake Booster was gone and it was causing a huge vacuum leak. They plugged up the line and disconnected the pump. Besides stiff brakes it ran better. Today I was driving home from work and my yj did something very strange; it started to stutter and hesitate A LOT when I gave it very little throttle. It would jump forward and sputter.

I got it home not too long ago and sprayed some carb cleaner around the base of the carb and the RPMs jumped up, i'm assuming there's a leak there.

Since taking it to the carb shop I've replaced the coil, the plug wires, the distributor cap & rotor. When using the timing light, I notice that the mark jumps up and down, not very much about 2º either while it's idling.

I haven't nuttered yet, I'm scared about emissions here in NV.

Where do I start?!!!
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Old 01-05-2010, 05:19 PM   #37
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I'm experiencing pretty similar behavior in my 91 YJ (stuttering under load, bucking when accelerating) and haven't been able to figure it out! I've replaced plugs, wires, cap and rotor and fuel filter, all because the bucking started when I almost ran out of gas.

Can running on fumes damage the timing chain?
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Old 01-05-2010, 05:47 PM   #38
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I have the same thing, 4.2L I6, MC 2100, Nutter, no Cat.
Mine does the exact same thing! Spits, sputters, calls me foul names, (wait.... that one's my wife)
What I do...
turn the key on, hit the gas pedal to close electric choke, after a second... start cranking.
Usually fires quickly, then dies.
Tap the gas pedal again, start cranking. Fires up and will rev up as carb opens.
Revs to about 2000 rpm. I let it go for about 5 - 10 mins. Kick it down to a normal idle, let it run a couple more minutes.
And away I go.
If I need to drive off without proper warm up, I'll drive off without kicking the idle down and let the electric choke work like it's suppose to.
If I try to push her before she's warm, she fights and bucks me till I give in.
I just resolve that it's the down fall of running a carb vs FI.
Hope this helps you.
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Old 01-05-2010, 05:50 PM   #39
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No not really Harrson . But you could of picked some trash or a little water .
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Old 01-05-2010, 07:58 PM   #40
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No not really Harrson . But you could of picked some trash or a little water .
It's been doing this for a few months now, so I'm not sure it's really a little anything. Could sucking up some gunk from an empty tank have damaged anything else?
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Old 01-05-2010, 08:26 PM   #41
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Carlyj,
you do have a carb base leak if the rpm went up when you sprayed around the base.
did you use gasket seal around the base and fill up the bolt slots in the adapter if you used a mr. gasket #1937 adapter and did you use a heat spacer gasket between the adapter and carb?
the timing mark will jump if the idle is not steady.
so make sure you seal the carb before thinking it could be something else.
And the nutter bypass is a great improvement.

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Old 01-05-2010, 09:03 PM   #42
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Carlyj,
you do have a carb base leak if the rpm went up when you sprayed around the base.
did you use gasket seal around the base and fill up the bolt slots in the adapter if you used a mr. gasket #1937 adapter and did you use a heat spacer gasket between the adapter and carb?
the timing mark will jump if the idle is not steady.
so make sure you seal the carb before thinking it could be something else.
And the nutter bypass is a great improvement.

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Scott, no I didn't use any gasket seal. I just pretty much slapped the spacer and the gaskets that came with the kit on there and closed my eyes. I sprayed the carb cleaner on the bottom of the base with the air cleaner off. When I put the air cleaner back on there was little or no difference when spraying the bottom of the carb; which I found odd. Wild goose chase?
I nuttered it tonight and I can notice a difference. I just hope I did it right! I didn't drive it enough to see if it still stuttered and sputtered; just around the block once but it seemed okay

So what you're saying is seal off the carb FIRST then look elsewhere? Will do.

I followed a diagram by buckshot on here and at first glance a lot of the ports on the diagram aren't even on my MC2100.



On the charcoal canister, the first line is going to the fuel tank. On my canister, the second line is the one going to the fuel tank. No biggy. Now the Carb. Vent from the canister, that port isn't there, because that's where I plugged in my distributor T along with the ported vac from the CTO. My PCV valve seems to plug into a large port on the back of the carb towrads the bottom which is also Td to the "Manifold Vacuum" on the diagram from the canister. The diagram also doesn't show the breather at the back of the valve cover. I have that one going into the top of the carb into a big port.

Video (sorry it's shaky):

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Old 01-05-2010, 10:53 PM   #43
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wow... lot of action on here.. glad to see everyone is helping everyone.. Jeep family - right scott? haha

alright - ordered my parts - and have a carb comming from scott - ( better start painting a picture for you)

timing light - gotta find one -
fuel pres. check - gotta get that done

thanks all for the help - ideas are flowing all the time..

later
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Old 01-05-2010, 10:57 PM   #44
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Quote:
Originally Posted by anklenawer View Post
wow... lot of action on here.. glad to see everyone is helping everyone.. Jeep family - right scott? haha

alright - ordered my parts - and have a carb comming from scott - ( better start painting a picture for you)

timing light - gotta find one -
fuel pres. check - gotta get that done

thanks all for the help - ideas are flowing all the time..

later
haha. it's a jeep thing Kyle! sorry about hijacking your thread, it was like a vision when i saw it and realized it was all the same stuff happening to mine!

i hope guam is treating you well and you get your yj fixed up soon!

thanks again for everyone's help.
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Old 01-06-2010, 12:08 AM   #45
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The nutter bypass was a good thing to do . Did you set the timing to 8 degree's with the vacuum advance unplugged at the dist. and the line vacuum line plugged with a golf tee or something while setting the timing? It must be set to 8 degree's after being nutted and with the rpm's at 680-695

You vacuum lines look fine . here in texas i was able to take off every vacuum line except the vacuum advance and pcv line.
It cleaned up my engine bay a lot.

But yes sealing up the carb if you thing you have any leaking is a good thing to do.

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Old 01-06-2010, 06:19 PM   #46
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carlyj, - don't worry about it man - if i can't figure out whats wrong with my jeep after all that help that i got - i may as well just run it off a cliff- haha

yeah, but scott - i got duty today( 24 hours of work) so i won't be able to e-mail you - but just send the carb to the address - whatever shipping you want - and let me know the price... i'll take care of ya man- you def. helped me out a ton...

thanks guys -
my status as of now - waiting for timing chain/carburetor...

she will run - also - i have to name her.... i was thinking because of her original condition.. naming her helen..as in helen keller - because she first didn't make any noise - and now she just stutters a little.. - is that too mean - it sure is funny - anyway-


later!
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Old 01-06-2010, 10:53 PM   #47
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Wow im having the same problem here too, just the small backfire part.
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Old 01-07-2010, 12:02 AM   #48
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Rebuilt ,if you have the 4.2 start with doing the nutter bypass , set the timing and adjust the carb and see if that fixes you up.

scott
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Old 01-07-2010, 03:31 PM   #49
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rebuilt -

listen to scott - he knows the ways of the jeep haha

do the nutter - my jeep starts faster and idles better

what carb do yo uhave? -= i have the weber... i don't think its working that well for me- getting the motorraft off scott - and replacing the timing chain/sprocket hopfulyl that does the trick..

good luck
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Old 01-08-2010, 09:54 PM   #50
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scott does seem to be very helpful and willing!
ok before we lay this to rest, i'd like to put some RTV on my carb to seal these leaks up. I bought some Permatex Red Fuel Proof. How much of this stuff should go on there? And should it just be a bead, like elmers glue? or should i lather this puppy up?

thanks!
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Old 01-09-2010, 02:38 PM   #51
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Carlyj you just want a thin film of sealant on all the gaskets to assure of a good seal but just a thin film of it.
tighten it down and in a few days while the engine is warm not hot tighten the nuts again holding the carb to the base.

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Old 01-11-2010, 01:26 AM   #52
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HIJACK....kinda.
I feel like I joined a club no one wants to be a member of.
Not the Jeep part, but the "I have a carb'ed 4.2l that doesn’t run right."
I have a 89 Wrangler that sat for 5 years. I spent 2 months getting it to start every time. Repairing problems from neglect is worse than from abuse.
After putting on a Motorcraft 2100 carb, HEI upgrade, and Nutter bypass it runs great…..almost all the time.
I went for a little drive. I live in Hawaii so there aren’t any long drives unless you go in a circle.
Was running great. Put about 50 miles on the road and 10 off. I get back on the road to head home and it starts to run bad again. #$*&$%#*. Hesitating and stumbling. Get within 2 blocks from home and now its starts bucking.
I am running out of things to throw my money at.
Changed –
Fuel pump
Rubber Fuel lines
Fuel filter (mounted with return line at top)
Gas cap
plugs (cap/rotar new with new distributor)
PCV valve (and grommet)
Flushed fuel tank and lines
Timing set to 8 deg BTDC (was at 12 when I did it by ear)
Can’t find any vac leaks.
I need magic that might not exist.
I would think that I need to give up and get another motor except that it does run so well…sometimes.

MentalBill

PS Do we need the O2 sensor after doing the Nutter bypass?
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Old 01-11-2010, 02:21 AM   #53
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Hello anklenawer and you to Scott, If you are having a problem that gets worst as the engine warms up then you weber is probably running rich like most do. You need a regulator like Scott mentioned for most webers. I ran webers and MC2100 carbs on my CJ and I had good results with both. If you are having a backfire then fuel is igniting in the exhuast sytem with usually means its too rich. You need the rich mixture when the motor is cold.
Adjustable Fuel Pressure Regulator 1-5.5 psi Inline - JTOutfitters
I ran this regulator on mine set for 3.5 lbs and it ran fine.
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Old 01-11-2010, 02:35 AM   #54
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Was running great. Put about 50 miles on the road and 10 off. I get back on the road to head home and it starts to run bad again. #$*&$%#*. Hesitating and stumbling. Get within 2 blocks from home and now its starts bucking.
PS Do we need the O2 sensor after doing the Nutter bypass?

How much time have you had it running since it sat for so long?
If you have a clean fuel filter and good fuel. Make sure you don't have any fuel lines running close to heat sources that may cause it to vapor lock as the engine heats up. You don't need O2 sensors.
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Old 01-11-2010, 01:34 PM   #55
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Well Mentalbill I would check to see if you have a wire mesh screen filter where the fuel intake line goes into the carb. it could be clogged up and causing the problem.
start motor spray carb cleaner at carb base to see if rpm's change . use can also check around the intake while your at it.
Recheck timing to see if it has moved or the timing chain/gears needs reset or replaced.
And of course check your air filter a dirty one can cause your problem.
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Old 01-11-2010, 03:43 PM   #56
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Wow you guys are quick.
I have had it running for almost two years. Put 7000 miles on it. Has 120k now. Most of that was with the stock carter carb. Tried like hell to not change it. I kept thinking that I could "fix" it. Gave up and just bought the MC2100 about 6 months ago. Started with this new problem about 6 weeks ago.
I will check the fuel lines tonight. I am stupid didn't even think of that (I had a '72 Datsun 240Z that had ALL kinds of trouble with vapor lock)
I don't remeber if it had the screen. I'll do that second or third depends if I get my friends timing light. I don't think its the air filter. Runs the same with no filter. I made this crazy dual filter that someday will connect to a snorkel.
And I hope this helps you (anklenawer) out also.
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Old 01-11-2010, 03:53 PM   #57
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I gave up. Took it to a mechanic and they confirmed then leak at the carb base. Even they couldn't fix it after sanding down the adapter plate. I don't even know what to do anymore! They told me to get a new adapter plate and gaskets and then bring it back but I don't even know where I would find those here in town or which part numbers they are. Help!@!
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Old 01-11-2010, 04:20 PM   #58
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mr. gasket any auto parts store part number 1937 or mrgasket.com

or you could just use red gasket sealer ( fuel resistant ) put a thin film on all gaskets and tighten it up and most likely that would take care of it.

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Old 01-11-2010, 06:37 PM   #59
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i'll try anything at this point. i already tried some other liquid gasket and the mechanic told me it didn't work obviously. i probably did it wrong.

anyone wanna skype with me tonight and try to tackle this?
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Old 01-12-2010, 10:49 PM   #60
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i got the stock carb on my jeep ill try the nutter let you know how it goes hopefully by tonight or tomorrow afternoon

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