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Unread 02-03-2007, 05:53 PM   #1
tippmann243
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1990 YJ Wrangler 
 
Join Date: Dec 2005
Location: st louis
Posts: 472
engine problems

welp im working on my jeep its a 1990 carb'ed 4.2 6 cylinder

i had a problem with it running like **** and it turned out i had about 30 vac leaks and a bad choke (made it hard to start)

anyhoo i deleted about a mile of vac hose and vac modulators that control emission crap.

i adjusted the carb mixture and reset the idle
adjusted timing by what the engine calls for and it runs like complete **** and wants to stall out and bucks and backfires under load. it would NOT idle with the egr hooked up. so it was left unplugged

then i reset the timing using a vac guage and it runs like a top, starts SUPER easy idles smooth, but it pings its *** off under a moderate load. i tired topping it off with premium fuel (92 octane) i put in 6 gallons (gives me an octane rating of ~88.5) and it still pings its *** off. this time it would idle with the egr working but it idle rough and would randomly stall out.

any input on what i can do to get it running good and get it to quit pinging.

im gonna try and figure out whats up with the egr valve tomorrow

thanks
-mark

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89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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Unread 02-03-2007, 08:47 PM   #2
Rivi
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turn the timing back a little at a time until the pinging stops.
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Unread 02-03-2007, 10:24 PM   #3
tippmann243
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Quote:
Originally Posted by Rivi
turn the timing back a little at a time until the pinging stops.
if we set the timing anywhere besides where it pull the most vac at idle it becomes hard to start, boggy and backfires out the exhaust/carb.
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89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
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Unread 02-03-2007, 11:05 PM   #4
Gregersonke
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Run a treatment of Seafoam through it... Should clean out the carbon deposits that were most likely building up over time in your engine and are the likely culprits for the pinging now.
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Unread 02-04-2007, 09:05 AM   #5
tippmann243
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Quote:
Originally Posted by Gregersonke
Run a treatment of Seafoam through it... Should clean out the carbon deposits that were most likely building up over time in your engine and are the likely culprits for the pinging now.
did that about 500 miles ago, all it did was give a nice smoke show
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89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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Unread 02-04-2007, 09:11 AM   #6
tippmann243
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well i guess i should give soem more details.

anything you cna think of i have done to this thing in order to get it running decent. well alomst everything besides replacing the carb for a webber unit.

so far i have
tuned it up and adjusted the carb idle mixture, it also has a jacobs? high energy ignition unit

replaced fuel filter

carb cleaned the piss out of the carb

cleaned the air filter (k/N)

the motor has a good ammound of blow by so i removed the one hose that blows back into the intake and vented it to the atmosphere

replaced the choke ( it was inoperable)

seafomed the motor (half can in the crank case half in the gas, whole can through the brake booster vac line)

i deleted a metric butload of that vac line BS that comes on these motors. so far that has helped the most in ease of starting and ability stay running
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89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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Unread 02-05-2007, 11:23 AM   #7
KrazyGimp
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What carb do you have in there? Is it by chance a Carter with a computer? If so you need to look into doing the nutter bypass. The computer in there controls the timing so no ammount of replacing parts or turning the distributor is going to help your pinging issues, because the computer is actually still trying to control it. Also, did you just start ripping out vacuum lines and what not? All of that stuff is interconnected. To remove all the emissions stuff you really need to just upgrade carbs and go with an HEI ingnition.

Here is a link that explains what all the junk under the hood is. I know its for a CJ but they are the same motor and share alot of the same emissions components.

http://home.sprynet.com/~dale02/
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Unread 02-05-2007, 01:26 PM   #8
blueknight44
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try removing the EGR valve, spray carb /injector cleaner on the piston, clean the carbon off.

Work the valve by hand until it moves freely.

I had bad carbon buildup that made the EGR valve stick and it wouldn't idle but it would run at a high speed then die.

Good luck.
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Unread 02-13-2007, 08:16 PM   #9
tippmann243
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1990 YJ Wrangler 
 
Join Date: Dec 2005
Location: st louis
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Quote:
Originally Posted by KrazyGimp
What carb do you have in there? Is it by chance a Carter with a computer? If so you need to look into doing the nutter bypass. The computer in there controls the timing so no ammount of replacing parts or turning the distributor is going to help your pinging issues, because the computer is actually still trying to control it. Also, did you just start ripping out vacuum lines and what not? All of that stuff is interconnected. To remove all the emissions stuff you really need to just upgrade carbs and go with an HEI ingnition.

Here is a link that explains what all the junk under the hood is. I know its for a CJ but they are the same motor and share alot of the same emissions components.

http://home.sprynet.com/~dale02/

thanks ill look into this

Quote:
Originally Posted by blueknight44
try removing the EGR valve, spray carb /injector cleaner on the piston, clean the carbon off.

Work the valve by hand until it moves freely.

I had bad carbon buildup that made the EGR valve stick and it wouldn't idle but it would run at a high speed then die.

Good luck.
did that the same time i seafoamed the motor, the diaphram moves flawlessly with now sticky spots
__________________
89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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Unread 04-01-2007, 03:45 PM   #10
tippmann243
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1990 YJ Wrangler 
 
Join Date: Dec 2005
Location: st louis
Posts: 472
welp i finally got around to working on the jeep again since im parking my blazer for some more mods.

did the nutter bypass and it runs like a champ, no more pinging and starts easier, it still needs a new carb but at least it runs good now

thanks for all the help guys
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89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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Unread 04-01-2007, 06:33 PM   #11
HiMiles91XJ
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Off topic, but how much compression does your 4.3 have, and how much boost are you pushing? Looks like you could hit 11's with that trap.
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Unread 04-02-2007, 06:04 PM   #12
tippmann243
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1990 YJ Wrangler 
 
Join Date: Dec 2005
Location: st louis
Posts: 472
Quote:
Originally Posted by HiMiles91XJ
Off topic, but how much compression does your 4.3 have, and how much boost are you pushing? Looks like you could hit 11's with that trap.
8.5:1 with 8 psi
__________________
89 blazer, L31/t56 28mpg.
blazer video, http://s29.photobucket.com/albums/c2...4091507-02.flv
1990 jeep, 4.2, 5speed.
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