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Old 12-31-2009, 11:21 PM   #1
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87 4.2l hesitant acceleration

87 yj, 4.2l, inline 6 - new plugs, wires, ignition coil, ECU and ICM -

set the timing so it will start and idle fine, but starting cold is hard - somtimes i think i am going to drain my battery.

thought i had a good running jeep until i drove it home - spitting and sputtering , hickuping and a little backfire out of the carb - especially UPHILL!!! -
i unplugged what i think was the 02 sensor, and the motor didn't have a difference. - so i am assuming thats bad - ( what i unplugged was right off my exhaust manifold, connected with 3 or so wires to a harness... and i just unplugged the harnis)

not sure what i can do here, i am doing to get a fuel filter right now, not going to get the sensor until you guys think its a good idea...

any help would be appreciated, i gotta drive this jeep man... its my only car

thanks

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Old 01-01-2010, 10:25 AM   #2
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Does it still have the stock Carter carb? That may be your issue. The O2 will have little effect on the running. I think before I spent the money on an ECU I would have ditched the computer and went with a different carb.

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Old 01-01-2010, 10:32 AM   #3
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Do the nutter bypass and see if that helps. It worked wonders on our 90yj and really easy to do
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Old 01-01-2010, 01:08 PM   #4
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This is a Picture Guide to Nutter Bypass

Here is a picture guide to the nutter bypass . it is a great improvement to the 4.2.
It made mine almost rev like a honda...lol
you will need 12 feet of 12 gauge of stranded wire 6 each org. and purple from radio shack will keep the factory color code.
when you done set the timing at 8 degree's adjust your carb air setting to make it rev and idle the best and you will be off enjoying more power and better mpg
give me a call if you have any questions
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Old 01-01-2010, 01:58 PM   #5
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Just a suggestion. Ditch the comp.,o2 sensor,and buy a motorcraft 2100 carb I found one on ebay rebuilt with all adapters ready to go. made a big big difference. Good luck
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Old 01-01-2010, 07:33 PM   #6
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wow!! thanks guys - just popped a fuel filter in there - not sure if that did much good - but its kind of hard to start - takes me about 20 cranks for it to turn -

anyway- was jut out messing with it - trying to check on the vacume lines - even thought the idagram is a headache - and i found this -could be very important


when its idleing - cold - it runs like it should - i can rev it up with no hesitation and no sputtering out the exhaust -

but after only about 5 min of idle.. it starts to shake a little - and the exhaust ( you have to go toward the back of the vehicle to hear this) sputters a little bit... and acts like its thinking about dying..

so - i will do the nutter bypass - and let you know - but i think this sounds like a vaccume problem maybe?!?!? because of the "build up" of failure...

thanks guys so much - really - you guys are awesome i will post after the bypass
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Old 01-01-2010, 07:40 PM   #7
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by the way - i got the weber carb -
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Old 01-01-2010, 07:49 PM   #8
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i have the same problem, some times i step on the gas and it doesnt go i say it almost gags on it self . by doing this nutter bypass will it help & is there any thing that else that i have to do with the bypass??
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Old 01-01-2010, 08:20 PM   #9
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Have you put your hand in frt. of the exhaust tip and made sure your exhaust is flowing free and your cat is not clogged up?
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Old 01-01-2010, 08:37 PM   #10
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No. I'm not sure how I would be able to tell the difference. Is there anyway to get a good round about if it's enough good flow from the exhaust?
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Old 01-01-2010, 08:54 PM   #11
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just have someone rev the motor while you see if the exhaust feels like it is coming out ok.
I just know that if the cat is clogged up the motor will run like you described.
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Old 01-01-2010, 09:07 PM   #12
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right on - just about to go and do the nutter bypass - basically just from the dist. to the ignition control module -

alright - here goes nothin'..

and i will check about the cat converter -

thanks a million guys - keep watching - i am going to post my nutter results in about an hour..

!!
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Old 01-01-2010, 09:38 PM   #13
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yep the org to org and purple to purple. set the timing to 8 degree's and readjust your carb settings and you will be amazed at the difference.
give me a call if you have a question. I am not feeling well and will be up late just watching tv.
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Old 01-01-2010, 09:45 PM   #14
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Is your carb equipped with an automatic choke? If so check and make sure its opening up once your motor is warmed up. and if all else fails giver her a compression test maybee you blew a head gasket mine was giving me the same problems when i found out it was blown.
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Old 01-01-2010, 10:34 PM   #15
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talked to scott about it - ( thanks again)

and the nutter helped start up time.. first crank and Boom... magic -

drove it around and still having a litle hickup here and there - up hills it will have to be first gear and just kicking the entire way -

didn't set the timing after the bypass, so i need to do that - and adjust the carb i guess - all in all...happy i got people to help

thanks a lot guys

will post with more news.
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Old 01-01-2010, 10:53 PM   #16
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a video of it doing its thing - slightly noticable only because its not pulling its own weight -

love my new iphone -haha.. just had to use a buddies car to get it haha


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Old 01-01-2010, 11:31 PM   #17
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its missing horiblt did u ever change the plugs wires and cap
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Old 01-02-2010, 12:09 AM   #18
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alright - checked out all the plugs - 3,4 and 6 didn't look so hot - i replaced them before i got it running - and all the attempts of trying ( with backfires) may have caused this - but it almost looks like black rust ( feels like rust) on those plugs - the other ones were kind of white - but looked ok.. here is a pic of a not so bad rusted one...



the more i drove it the worse it got - but i replaced the new plugs ( rusty ones) with old ones just to see - and it seemed to have ran better - didn't want to die - just coughed a lot - so i'm getting new plugs for sure - then want to get the timing exact - other than that - the warmer she gets - the worse she gets - putting a lot here to get a lot out

thanks a ton guys
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Old 01-02-2010, 01:17 AM   #19
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talked to scott again on the phone - and noticed that on my weber carb.. when i accelerate through the linkage on the back of the carb... only one - ( the left one) squirts fuel into the carb.. the other is dry - doesn't even drip i don't think - so i think thats the problem -

should get the new carb, but is there another vehicle i could putt it off of? or even clean this one out well enough to wait two weeks for the other come come in?

thanks
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Old 01-02-2010, 03:03 AM   #20
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take her apart and clean it see if that does it. Also did you notice if your motor is running at its usual temp, or is getting pretty hot
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Old 01-02-2010, 07:38 AM   #21
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I don't know much about the Weber carb, but if it's only pumping gas out of one inlet and not the other, than I would think a good, thorough cleaning would be a place to start. Maybe someone on here has a good link for the procedure?
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Old 01-02-2010, 07:46 AM   #22
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it does get hot!!! quick - i thought so.. i just wasn't sure -

i hope thats an idication of a Dirty Carb.. any instruction on how to clean the weber - i would love that - first thing tomorro w-

how do i make sure that i clean the "squirt " part - haha

thanks guys -

kyle

call me if you have any ideas - 671-777-6365

thanks
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Old 01-02-2010, 04:29 PM   #23
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Yep Kyle it is time to pull the carb apart for a good cleaning .
To get you by with the weber until you can get a mc 2100 and in Gaum you will want to have a 47 or 48 jet in it.
You will also want to do a compression just to make sure you don't have a burnt valve .
And if none of this helps go ahead and replace the dist cap and rotor since it seems to get worse as it warms up and if it has a hairline crack it could cause your problem . Like i said run it at night when it is real dark and look at the dist. cap , wires...ect to see if you can see it arcing anywhere. And if no problem there then you might try a new icm it could be breaking down when it warms up also.
Hang in there Kyle you will figure it out.
Looks like a nice yj . You will love driving it and in return it will turn you into a top notch Jeep mechanic ...so now you understand it's a Jeep thing
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Old 01-02-2010, 09:11 PM   #24
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post carb clean

took off the weber - not so fun - but i got it off

and sprayed carb cleaner in the jets and got a lot of gunk out -

took it for a run -

after i got it started - it was idleing rough for a mini - they got right a nice steady pur..

accellerating was alright - a lot better and have a good amount of power. but one again - at about 3000 rpms it would skip a little bit - doesn't backfire though - ( unless slowing down the hill in second and so forth) so its better - amd i am going to order the motocraft carb for it -

and new plugs... because the other ones were shitty - but its pretty much drivable now... so thanks - but its not cherry ... i'll get there -

thank you guys for your help - i will be on here posting new stuff about when i get the plugs - but all in all -

thank you scott for your help - ( especially at 630 am....) haha

kyle -

anklenawer@gmail.com
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Old 01-03-2010, 02:53 AM   #25
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post new plugs update -

alright - so if you have been reading - i have been working on the jeep pretty much the entire weekend - but thats alright - i'm learning a lot

after new plugs though - same thing - in fact, when it gets the juice right - it jerks me back - a lot more power , but when it skips out and sputters - ( which is still does) it makes me cry a little -

as i have said before - the warmer it gets - the worse it gets

after start up - i rev it and it seems just fine.. after the belts stop squeeling...it runs fine - take it for a spin - first gear - almost great - 2nd gear - more juice - more uphill... worse - went up to watch the sunset with the lady- and when i got to the top - it was the same as before - as i was going back home - more sputtering...and then started to backfire out the carb a little even..

maybe another cleaning? i'm ordering a new carb tonight , but i'm not sure what i can do around that to make sure everything is good... - because if i buy this carb...and it still does the same thing - i am probably going to take it in... and use some of my savings.haha..

well - any other tests i can do to help diagnose this??

thanks everyone -

kyle
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Old 01-03-2010, 08:45 AM   #26
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Unless you have a vacuum leak odds are it is in the carb. Webers are overcomplicated and either work ok or are crap. Go with the motorcraft and don't look back. You will regret not doing it sooner.
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Old 01-03-2010, 12:04 PM   #27
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Hey Kyle,
Just make sure when you put on the new adapter for the mc2100 that you use gasket seal so you won't have a vacuum leak .

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Old 01-03-2010, 01:51 PM   #28
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As always. Thank you so much. I'll try to find a temp carb for this or clean it again. Because two weeks is a long time for a maybe. But I have a feeling I would be going to that carb anyway, so I'll see if my buddy has one for me. Or at least if we can swap for a test drive. Other than that, timing light! I really can't believe how helpful you guys are. And to think the world was going to hell because of this damn Internet. I guess it is useful !!! Also. I'll mess with the mixing screws. Maybe that will help. If it gets better I will know ITS the carb

thanks

Kyle
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Old 01-04-2010, 05:49 AM   #29
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no real news - had to be a sailor today ( in the navy ) but i took the carb off and tried to clean it - i wouldn't get the carb itself to separate - and didn't really know what i was doing anyway - so i just seen every opening and spreyed carb cleaner in it -

this may be a good thing to add..

i blew into the fuel line - ( got an eye full of my own gasoline flavored breath in my eye from the air nozzle haha)

anyway - it seemed pretty hard to blow in there - messed witht the linkage while blowing - no difference - but it seemed to get harder and harder to blow every passing time ( a series of 8 breathes or so.. iwas getting light headed - haa)

not sure if that has anything to do with it - tomorrow my buddy is going to get a pressure gauge for the fuel -

also - do i have a regulator - where would it be?

thanks guys

kyle
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Old 01-04-2010, 10:12 PM   #30
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The fuel pressure regulator should be located in the fuel line right before the carb and if i am not mistaken should be adjusted to 3-4 psi for a weber carb.

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