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Unread 02-22-2010, 01:25 PM   #1
yoda604
Registered User
1989 YJ Wrangler 
 
Join Date: Feb 2010
Location: Langley, BC
Posts: 181
1989 yj loss of power

Hi everyone,
New to this site, my first post of a problem and boy do I need some help.

I have a 1989 YJ I6 4.2 carberated engine. Now I have just recently bought this jeep. and everything worked. I have done some minor stuff to it so far. New tires (33" Cooper Discover SST's Already had a 4" susp lift) New tie rods and ball joints. I have had it for 2 weeks and have taken it offroad like 4 times. Absolutely love this jeep.
I have however not heard to many good things about the 4.2 engine. And just recently drove to edmonton from langley (1200km or 750 miles) Lots of elevation change and mountain roads. For about the first 600-700 Kms she ran perfect. After that I started to loose tons of power. and for the last 600 kms was only able to do about 80kms an hour (50m/h) in forth gear only if i found that sweet spot in the pedal. As soon as I would try to put it in fifth I would loose all power. 1,2 gears worked fine, 3rd was like forth (had to find that sweet spot in the pedal). All other gauges read correctly (fuel, temp, oil pressure, volt)
I got it to my cousins shop and we had noticed that the butterfly valve was completely shut. we opened it and lubed all of the pivot points and changed the fuel filter and the PCV valve. Took it out for a boot and the jeep seemed to be fine, then the problem happened again. So we checked the cap and rotor and there is plenty of spark at the plug. Checked and there was no power to the auto choke. so we just disconnected it and figured we could just use the choke manually. Worked for a bit and then huge loss of power again. Also now the volt meter works periodically and the oil pressure gauge needle is buried, which is not right, and makes me think that there is obviously some grounding issues somewhere.
I had to get to work and have now flown back to langley and had to leave my jeep behind. And I hate leaving a man behind. I'm flying back out to edmonton this weekend. My cousin is going to be looking at it all week and when I get out there I'll be working on it to.
Anyways, any suggestions? Anybody had this problem before? Is it because of the elevation change? do I need to change the jetting in the carbs?

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Unread 03-02-2010, 01:27 PM   #2
yoda604
Registered User
1989 YJ Wrangler 
 
Join Date: Feb 2010
Location: Langley, BC
Posts: 181
Thanks for all the help on this one guys.

But i did figure it out so I thought I would share the info with whoever reads it. Turns out the auto choke for the carb had no power, also the vacuum line that opens and closes the air filter intake was toast. So I ran a new lead in for the auto choke and just pinned up the air intake flap.

Runs at a top.
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fuel , loss , miss , power , spark

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