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View Full Version : 4.2 runs like a three legged dog


89yj
05-07-2006, 01:59 PM
I've got an 89 yj with that terrible computer controlled carb and it misfires, stumbles when you give it gas and pretty much runs like crap. Any ideas?:confused:

bakelite
05-07-2006, 02:04 PM
yeah, I think it's called the "nutter" bypass.....not sure, I lost the link. Mikey will know. (Nutbar)


I got a 4.2 also and it's totally shot [15] holed piston I think. 9 quarts of oil from maple ridge to lac la hache

bakelite
05-07-2006, 02:11 PM
found it...lots of good info here

http://www.jeepsonly.com/How_Tos/Engine_Upgrades/


this is the one you want I think

http://www.4x4wire.com/jeep/tech/electrical/jn-ignition99/ ...seems kinda screwed up right now (the site) but the info is there[cheers]

Nutbar
05-07-2006, 09:42 PM
Check it for an intake gasket leak they are very prone to them, and definately check out that link and do the the carb and ignition modification to that 4.2 you won't be disapointed it makes a huge difference on how they run and way more power.

89yj
05-07-2006, 10:47 PM
Has anyone done that swap where you put the 4.0 head on 4.2. I've heard alittle about it but would like to know how hard it is, what's involved and if it makes a difference. Also will it work with the computer bypass. This is my daily driver for the family so I need it to be reliable.

Nutbar
05-08-2006, 12:12 AM
Unless you are going to do the whole cylinder head and fuel injection on to the 4.2 it isn't worth doing. Just doing the cylinder head won't add much to that 4.2 engine with the stock manifold and carb and you also have to use the 4.0 exhaust manifold because the bolt hole locations for the exhaust man change also the intake ports are repositioned on the 4.0 head, the intake man will bolt on and seal but you will create turbulance in the air flow any ways because the ports don't match up quite right and negate most of the gains that the redesigned intake ports on the 4.0 head are supposed to give.

pumpkin
05-08-2006, 12:21 AM
Just do the manifold and head swap Mikey did, it will run great and double the power[15] [f]

Nutbar
05-08-2006, 12:23 AM
Just do the manifold and head swap Mikey did, it will run great and double the power[15] [f]


[22] [f] [f] Your an ass Bob lol[15] [15] [15] [cheers]

bakelite
05-08-2006, 07:51 AM
Your welcome. [16]

89yj
05-08-2006, 06:16 PM
thanks guy's for all the info. I think I'll do the bypass for now and save up for an engine swap. [cheers]