90 YJ 4.2L with weber carb and CRT HEI misses at idle, pings, and has NO POWER! - JeepForum.com
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post #1 of 12 Old 11-04-2008, 04:32 PM Thread Starter
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1990 YJ Wrangler 
Join Date: Nov 2008
Location: north carolina
Posts: 7
90 YJ 4.2L with weber carb and CRT HEI misses at idle, pings, and has NO POWER!

I have a 90 YJ 4.2L with a 32/36 DGEV Weber and I have just recently installed a CRT HEI dist. I am a new member and this is my first thread on this forum and i am in serious need for some help. I am going to be as specific as possible about my problems.

PROBLEM #1 my jeep misses all the time at idle whether its warmed up or not and i cant determine if its because of the carb or ignition(ive tried the idle mixture screw and i cant get it any better). The major thing i have noticed is that the exhaust smells bad all the time but it is TERRIBLE when the engine is just starting to warm up just a couple mins after its been started. I want to think its running rich but im afraid if its an ignition miss then all i am smelling is unburned fuel in the cat. BUT i had this problem before i put the hei on my jeep.

PROBLEM #2 I removed the new spark plugs i installed with the dist. recently and noticed that all of them were burned on only one side.(one side white and one side black). I was told that i had the wrong heat range and that the Bosch platinum plugs i had were junk. So i just bought regular champion plugs because i don't think i need special plugs for the hei setup and i didnt noticed a difference in the miss.

PROBLEM #3 (my biggest headache) The hei is suppose to be set at 8 deg BTDC at 1600rpm. Well i set it to that with a timing light and the motor sounded like it had an exhaust leak. Not only that but it was so under powered i could barely take off. But it seemed to pick up a bit around 1500 RPM but i still couldn't get it above 55mph on the highway holding it to the floor! So i advanced the timing (to about 16 deg BTDC) and i noticed an improvement instantly and i can get to 70 mph on flat ground but the minute i hit any sort of hill it just slowly loses speed no matter how hard i push the gas and i can hear what i am almost positive is pinging.

I know that my 4.2L shouldn't have trouble running down highway at 70 MPH with 4.11 gears turning 33's!

I think these problems are all related but i wonder if anyone has had any or all of these problems with there engine. Sorry about the long thread i just want to be thorough.


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post #2 of 12 Old 11-04-2008, 04:50 PM
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1989 YJ Wrangler 
Join Date: May 2006
Location: under my jeep
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how did it run before the crt and the weber?
check these out...not sure if this is it but it would be the first thing i would check...

as far as timing...don't worry about the timing until you get the hesitation/miss taken care of...and how i time mine? Start at about 12-14 deg advanced and then give 'er hell in 2nd gear (try to get to 4k rpms)...if you hear it "ping (probably around 3k) pull over and retard it a bit...do the test again...if you can get to 4k and not have any pinging i'd say your close

and my plugs are the same way...brown/tan on one side, white on the other...i think it's fine

let us know what you find out.

Good luck

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post #3 of 12 Old 11-04-2008, 05:36 PM
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1996 ZJ 
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Location: Vernon, NJ
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The HEI is set at 8* at curb idle (600-800 rpm) NOT 1600! The vacuum advance should be connected to PORTED vacuum and disconnected and plugged while setting the timing. The 1600 rpm is only for the stock carb and pulse air setup. Your timing is way out of whack.

96 ZJ.
05' Grand Cherokee Limited, 2"OME lift
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post #4 of 12 Old 11-04-2008, 07:25 PM Thread Starter
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1990 YJ Wrangler 
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Location: north carolina
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thanks dbikers for those links i still need to check my dist. to make sure the cap isnt cracked and i will try timing it like you said. but have you had any problems with cruising down the interstate at about 70mph?
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post #5 of 12 Old 11-05-2008, 03:08 PM
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1988 YJ Wrangler 
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Location: Port Severn, ON, Canada
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I too have the same issue as you and think its timing. Down hill im flying, any incline and no power and have to downshift and still no power. Do you have any pics of how you connected your advance vacuum? Mine is connected to the carb directly but t'd as in the diagrams i have been seeing Elvis had on his writeup.

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post #6 of 12 Old 11-05-2008, 05:37 PM
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1987 YJ Wrangler 
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set the timing with a vacuum guage, connect the vacuum guage to manifold vacuum, rotate the distributor and find the highest vacuum, should be around 21 inches, then turn the dissy clockwise till vacuum starts to drop, tighten dissy. this sets the timing to the motor, this is the only way I could get mine to run right.
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post #7 of 12 Old 11-05-2008, 06:22 PM
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1987 YJ Wrangler 
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I have a similar setup (just a MC2100 carb and CRT HEI rather then a weber) and my setup runs great, but only with timing set around 20-22 degrees. I've set it as curb idle, around 7-800rpm. I'm not running a vac advance (not needed because of centrifugal advance in the dist.) I'm happy with the way it runs, I tried setting it to about 11* and it sucked. Was like trying to drive a 3400 lb. lawnmower. Set it back to 22* and it runs like a champ, pulls hard.
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post #8 of 12 Old 11-05-2008, 06:35 PM Thread Starter
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1990 YJ Wrangler 
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Location: north carolina
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i dont have any pics but my vacuum advance is running directly to the to the port on the carb, no T. and i think advancing the timing will help i just dont want to go to far with it
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post #9 of 12 Old 11-06-2008, 05:50 PM Thread Starter
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1990 YJ Wrangler 
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Location: north carolina
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Ok i set the timing with a vacuum gauge and was able to to get 20.5in of vacuum. when i reved up the engine and held it i had a steady miss but when i unhooked the vacuum advance the miss went away. so i backed the timing off a bit and eliminated the miss and im now pulling about 19.5in of vacuum. it also took care of the miss at idle. it definitely runs better but now whenever i am under load on the highway and start to open the secondary it starts to ping loudly and doesn't pick up any speed. Could something be wrong with my vacuum advance?? my CRT Performance dizzy is only a month old. They say it can be adjusted by a screw but i don't know how to go about adjusting it. Thanks for the help so far.
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post #10 of 12 Old 02-16-2009, 08:48 AM
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Bigbluefan5, did you ever get your problem figured out?
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post #11 of 12 Old 04-12-2009, 09:04 PM
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this is my 1st time on the forum...
I am having the exact problem on my yj, all strted after the 32/36 weber was installed, no power, cant break 55 on hills i pray i make it over, sounds like it miss fires...
I live in NY long island, took it to a friends shop had the timing adj, carb tuned was told 2 thing - said the carb was bad, yet was brand spanking new, or the main to be re-jeted ..
any other clues or things i can do
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post #12 of 12 Old 04-27-2009, 12:56 PM
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1978 CJ7 
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Jeep 4.2 and the proper Jets and Tune can be found here, also how to read your spark plugs and how to make you Jeep run better. Also be very carefull with the HEI in Jeeps they are known for two much advance too early and can hurt your engine. This is a good read and has lots of links that can show you the way.


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