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Old 12-03-2012, 05:57 PM   #1
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1990 Jeep YJ

I have a 1990 Jeep YJ with 4.2l and it is a auto with 410 gears. When I driving on normal roads and I get to a steep incline it looses power I can go is about 40 mph. Has any one added fuel injection to your 4.2 and if so diod it help with power.

Thanks

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Old 12-03-2012, 09:40 PM   #2
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Is this a new problem, or has this been a problem slowly getting worse?

Any recent repairs, or tune ups?

How many miles?

With a 4.2L auto and 4.10 gears you should have some serious get go, and unless you were running HUGE tires or towing a lot of weight there is no way it should drop to 40 on any incline.

I would suggest checking it out, doing the quick and easy checks and maintenance, but I dont think installing fuel injection will fix that kind of problem. You would be better off, and much cheaper, to replace the carb. But overall I think there is a problem that needs to be found before anything else.

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Old 12-03-2012, 09:50 PM   #3
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Quote:
Originally Posted by camarozz View Post
Is this a new problem, or has this been a problem slowly getting worse?

Any recent repairs, or tune ups?

How many miles?

With a 4.2L auto and 4.10 gears you should have some serious get go, and unless you were running HUGE tires or towing a lot of weight there is no way it should drop to 40 on any incline.

I would suggest checking it out, doing the quick and easy checks and maintenance, but I dont think installing fuel injection will fix that kind of problem. You would be better off, and much cheaper, to replace the carb. But overall I think there is a problem that needs to be found before anything else.
x2..tune up,check carb,check for clogged exhaust..our 4.2's don't even have 4.10 gears and they will haul ass
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Old 12-03-2012, 10:19 PM   #4
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camarozz was wrong on one thing, you will not be better off replacing the carb, Fuel Injection is superior in many ways, but the price is steep too.

The Howell kit is about $1200. and is a TBI setup found on the GM 4.3L v6.
The Chrysler kit costs about $2500. and is a Sequential Port Injection setup found on the 4.0L HO engines Jeep engines.
Both have emissions legal versions for the same price.

A factory carb, rebuilt correctly, should cost you about $300-500.

An E-bay carb kit costs about $250, and is NOT emissions legal in emissions states.

FYI: California is the WORST emissions state, and I see your in Cali....
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Old 12-03-2012, 10:30 PM   #5
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camarozz was wrong on one thing, you will not be better off replacing the carb, Fuel Injection is superior in many ways, but the price is steep too.
Well, not wrong necessarily, I was not suggesting FI was not superior, just that the investment is not worth the benefits. Not to mention it would not fix his problem.

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The Howell kit is about $1200. and is a TBI setup found on the GM 4.3L v6.
The Chrysler kit costs about $2500. and is a Sequential Port Injection setup found on the 4.0L HO engines Jeep engines.
Both have emissions legal versions for the same price.

A factory carb, rebuilt correctly, should cost you about $300-500.

An E-bay carb kit costs about $250, and is NOT emissions legal in emissions states.

FYI: California is the WORST emissions state, and I see your in Cali....
Not knowing the OP and his skill set, but I rebuild them for about $100 in parts, and thats if I modify them to perform better than stock. Typically a $20 kit works fairly well too.
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Old 12-04-2012, 09:41 AM   #6
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I have 31x12.50x15 tires and it has been like this since I bought it. I have checked the tune and it passes smog with no problem.
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Old 12-04-2012, 09:50 AM   #7
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I have 31x12.50x15 tires and it has been like this since I bought it. I have checked the tune and it passes smog with no problem.
How long is that?

Could be cat is clogged.
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Old 12-04-2012, 03:25 PM   #8
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How long is that?

Could be cat is clogged.
sounds like it..my wife runs 31's on her 4.2 and it will run as fast as you want to hold it
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Old 12-04-2012, 04:25 PM   #9
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How long is that?

Could be cat is clogged.
This. With those symptoms it's most likely a clogged cat.
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Old 12-04-2012, 07:32 PM   #10
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Agree, check you exhaust pressure coming out of the tailpipe. Have you checked your vacuum lines to make sure there's no cracks to cause irregualr power?
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Old 12-04-2012, 08:08 PM   #11
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Clogged cat, or leaking carb DUMPING fuel.
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Old 12-05-2012, 11:11 AM   #12
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Loss of power and overheating are two symptoms of clogged cats. My 4.2 with 3.55's runs like a scalded dog (comparatively, it is a Jeep) and climbs hills well at highway speed. Grabbing 4th it scoots right on over.

Have you checked the fuel filter? Then check the pressure at the fuel rail. Not sure but I would think it should be 35-40#. This will tell you if your pressure regulator and fuel pump are ok or not. Sounds like your not getting adequate fuel supply.
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Old 12-05-2012, 12:59 PM   #13
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Loss of power and overheating are two symptoms of clogged cats. My 4.2 with 3.55's runs like a scalded dog (comparatively, it is a Jeep) and climbs hills well at highway speed. Grabbing 4th it scoots right on over.

Have you checked the fuel filter? Then check the pressure at the fuel rail. Not sure but I would think it should be 35-40#. This will tell you if your pressure regulator and fuel pump are ok or not. Sounds like your not getting adequate fuel supply.
4.2 has a carb..fuel pressure less than 10 pounds..5 or 6 is plenty
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Old 12-05-2012, 01:12 PM   #14
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Quote:
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4.2 has a carb..fuel pressure less than 10 pounds..5 or 6 is plenty
X2
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Old 12-05-2012, 03:38 PM   #15
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Originally Posted by 90DesertTanYJ View Post
Have you checked the fuel filter? Then check the pressure at the fuel rail. Not sure but I would think it should be 35-40#. This will tell you if your pressure regulator and fuel pump are ok or not. Sounds like your not getting adequate fuel supply.
Fuel Rail? your thinking its a 4.0L with PFI, he has a 4.2L with a CARB.....
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http://www.wranglerforum.com/f330/2x...ad-490865.html
'04 SV1000s:
http://www.svrider.com/forum/showthread.php?t=280873
Old Jeep that was totaled (and SOLD!):
http://www.wranglerforum.com/f330/2x...ad-101879.html
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Old 12-06-2012, 10:35 AM   #16
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Duheeeee! Boy got that mixed up in the same post. Talked about my 4.2 and immediately went into talking FI.

Must be Old Timers gettin to me.

Still stand by my fuel filter idea.
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Old 12-06-2012, 01:38 PM   #17
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I already checked the fuel filter. I am going to check the cat. Thanks for all the ideas.
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Old 02-12-2014, 01:43 PM   #18
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I solved it with a Mopar fuel injection kit. This thing has come alive.

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