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Loss in power on 4.2L

Loss in power on 4.2L
kaotik1

kaotik1

Jeeper
Posts
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Location
Albuquerque NM
Vehicle(s)
1984 CJ7 Loredo 4.2L
So I just picked up a 84 CJ7 AMC 258 i6 / 4.2l and had it shipped to me. Owner said it was in perfect running condition when I received it the jeep starts right up but after driving it for a while it loses power and doesn't want to accelerate and basically starts putt-putting..also it randomly shuts off at stop lights but will start right up. Any one have any idea what might be causing these issues? From what I can see it has a new holley carb.
 
Two possibilitys come to mind, first would be a bad ignition control module. It is located behind the windshield washer bottle as a square metal box. If it is hot to the touch after running a short while, that needs to be replaced. Second would be the distributor pick up coil, which would be easiest to just get a reman one. To test this you should get 600-800 ohms between the orange and purple wires coming out of the distributor.
 
Is the coil get'n to hot to hold onto? Do you still have the OEM horseshoe connettor on the coil. It is a well know problem area for poor contact.
Ck the 2 items Torxhead speaks of.
Replace the fuel filter and fill the tank with premium fuel.
Good luck
 
I'll add the Catalytic converter to the above list of things.
 
Lumpy Grits said:
Is the coil get'n to hot to hold onto? Do you still have the OEM horseshoe connettor on the coil. It is a well know problem area for poor contact.
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I had this problem I would be going along and it would just quit so this is what I did.
 
kaotik1 said:
So I just picked up a 84 CJ7 AMC 258 i6 / 4.2l and had it shipped to me. Owner said it was in perfect running condition when I received it the jeep starts right up but after driving it for a while it loses power and doesn't want to accelerate and basically starts putt-putting..also it randomly shuts off at stop lights but will start right up. Any one have any idea what might be causing these issues? From what I can see it has a new holley carb.
Click to expand...

So what did the former owner say about this problem?
 
Torxhead said:
Two possibilitys come to mind, first would be a bad ignition control module.
Click to expand...

I second this one immensely. I had way too many problems with mine in the beginning due to this ridiculous little device. Even new ones can be bad. Had to shop around until I found a new one that worked. They are heat sensitive so they may not start to fail until you've driven it a bit and the engine has warmed up or gotten hot.
 
Neuner said:
I second this one immensely. I had way too many problems with mine in the beginning due to this ridiculous little device. Even new ones can be bad. Had to shop around until I found a new one that worked. They are heat sensitive so they may not start to fail until you've driven it a bit and the engine has warmed up or gotten hot.
Click to expand...
Do you have the brand and model you went with to help save me the trouble?
 
hagar said:
So what did the former owner say about this problem?
Click to expand...
The owner denied everything and said the vehicle was working fine. Not sure if this matters but the Jeep was purchased from Denver and brought over to Albuquerque so not sure if elevation has a factor in any of this.
 
Only had to purchase one BWD Select that worked the first time. The others commonly found at local parts stores failed for me multiple times. I didn't try anything from Napa. Their store closest to me sucks.
 
I got my icm from N.A.P.A., their Echlin brand, and at the time it was about $80, which was around 8 or so years ago. I would advise clipping the black ground wire from the distributor harness and running it directly to the battery. This provides a direct ground to the icm, rather than the distributor. Is the icm the problem here?
 
Check for water in fuel, flogged air filter, spark plugs. Anything that a rich mixture would cause or contribute to fouling plugs.
 
If your above 4K'(ASL)there's a GND wire new the coil bracket(if it hasn't been removed)that resets everything for higher altitude.
Altitude Jumper

Lots of good info here.
Table of Contents

How much in 'mods' has the PO done to the wiring etc.
can you post some pictures so we can see?
LG
 
so I ended up taking the Jeep to the shop to take a look at it.. looks like the previous owner hadn't done any maintenance in a while.. I had them run a compression check on the engine and engine was fine they ended up replacing the head gasket as oil was coming out of the head also water was found in the head. they cleaned that out and changed the oil that was also gray and probably hadn't been changed in years. They also did a carb tune and adjusted the timing as well as a few other things like changing the oil in the rear and front diffs. After all of that the jeep started right up and stopped smoking but still seems to lack power I mean the jeep really lags and feels like its struggling while going up inclines as well as accelerating from a stop. Anyone have anything else I can take a look at.. I also noticed quite a few exhuast leaks and am going to replace all the exhaust piping and muffler in the next couple of days as the original setup was pretty rough and rotted.
 
Hedgehog said:
Check for water in fuel, flogged air filter, spark plugs. Anything that a rich mixture would cause or contribute to fouling plugs.
Click to expand...
^^^^ See in red....somebody done flogged that air filter:eek::eek::D :chug:
:poke:
 
Hey ... hey ... hey - A filter covered in mud and grass could be considered to be flogged, a better word would have been clogged though. :) yep I'm an *** sometimes and generally deserve what I get ...

The inline 6 isn't really street powerful and Albuquerque NM isn't exactly flat ground. If were you I'd keep a very close eye on your oil. If it starts to get milky you've got real problems to deal with. If not an HEI type ignition will do a better job of lighting the fire. Other fairly common performance enhancements can help. .... Then things can get spendy like adding EFI ..... Or you can spend real money and time by swapping things out
 
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kaotik1 said:
The car doesn't have a cat just header to muffler
Click to expand...

Car? Sorry, I thought you were referring to your Jeep. I don't know anything about your car.
 
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