engine and ecm on 1990 yj 4.2l carb'd???? - JeepForum.com

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post #1 of 31 Old 09-27-2011, 12:46 AM Thread Starter
AmmitOsiris
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engine and ecm on 1990 yj 4.2l carb'd????

Hi I need to know all I can get about my engine please let me know it is much appreciated

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post #2 of 31 Old 09-27-2011, 09:07 AM
89yjsahara258
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http://home.sprynet.com/~dale02/list.htm

I found this very helpful. I also have the 1990 FSM so if you tell me what you are trying to do I can send you the section(s) you need.

Spencer
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post #3 of 31 Old 09-27-2011, 12:09 PM Thread Starter
AmmitOsiris
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I wanna know what the ecm controls but theres more I need to know I'm in school right now
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post #4 of 31 Old 09-27-2011, 12:13 PM
Old4X
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Your ecm controls idle mixture, ignition timing, pulse air system, and idle speed.

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #5 of 31 Old 09-27-2011, 12:37 PM Thread Starter
AmmitOsiris
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Ok so can I tune the ecm so I get more horses or torque for better performance?
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post #6 of 31 Old 09-27-2011, 01:05 PM
89yjsahara258
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No it does not function that way. Unless you figure out how to make the sensors lie you cannot change the programming. Search the Nutter Bypass. This removes the computer and helps with power. I have done this and my engine wen from bogging down at 2800rpm to pulling all the way to redline.
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post #7 of 31 Old 09-27-2011, 01:06 PM
89yjsahara258
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Just noticed your from Cali where I think that mod is illegal. The Howell EFI kit is an option however and they make one legal for your area.
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post #8 of 31 Old 09-27-2011, 03:31 PM
NonRubicon
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Quote:
Originally Posted by AmmitOsiris View Post
Ok so can I tune the ecm so I get more horses or torque for better performance?
The link posted up by 89yjsahara258 is THE definitive online resource for getting to know the engine setup you have.

The ECM is crude at best, there is no way of retuning it that I know of. It is pre-OBD1/OBD2. There aren't even any aftermarket readers for the diagnostic ports (you have to make your own). The computer is programmed to keep the A/F mix as close to the 14.7:1 ratio as possible by bleeding-in/cutting-off air in using the stepper motor pins at the rear of the carb body. Disable the computer by doing the Nutter Bypass and you could retune the carb for better power, but you might not pass emissions and stay street legal.

Here in CA, our street legal options for the 1990 4.2L YJ are:
  1. Sticking with the Carter BBD. Its a decent carb, but it takes alot of work and polishing to keep it running well. You cannot swap in any other carb.
  2. Upgrading to the California Howell TBI kit. Pricey, but from my experience with it so far, its worth it.
  3. Upgrading to Mopar MPFI kit. Expensive. Really expensive.
  4. Engine swap to something fuel injected like the Jeep 4.0L

The Howell and the Mopar kits are C.A.R.B. approved kits.

You might be able to get better performance by putting in an MSD ignition module.

The Team Rush upgrade is something that I think every 4.2L should have done to it.

Welcome to the 4.2L club.

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post #9 of 31 Old 09-27-2011, 04:22 PM Thread Starter
AmmitOsiris
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Well the jeep itself is canadian and it as a weber carb on it. Are there any engine mods I can do to pump the horses and torque up?
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post #10 of 31 Old 09-27-2011, 04:24 PM
superj
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mine is canadian too but that carb is not stock. you will fail your inspection in cali.

I don't feel like working on anything at this time so i sold my yj.
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post #11 of 31 Old 09-27-2011, 04:25 PM Thread Starter
AmmitOsiris
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I passed with flying colors.... this is how I bought it
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post #12 of 31 Old 09-27-2011, 04:29 PM Thread Starter
AmmitOsiris
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Any engine mods?
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post #13 of 31 Old 09-27-2011, 04:35 PM
superj
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you ahve it, the weber.

yours is not an ecu like a honda or a street racer. its a very very basic ecu that now is not doing anything since you ahve a weber and not the stock carb.

put a cali legal header on it or fuel injection.

I don't feel like working on anything at this time so i sold my yj.
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post #14 of 31 Old 09-27-2011, 04:41 PM
DocWills
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If you replaced the carb, or whoever did, it lost most if not all the crap lol. Add a ground, do the team rush, you will need to leave stuff in even if its not working to pass emissions out there. I got a 90, replaced the carb as you did, if your ignition box gives trouble think of upgrading.
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post #15 of 31 Old 09-27-2011, 04:44 PM Thread Starter
AmmitOsiris
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I'm thinking of throwing MSD stuff in it. And do you you know what engine mods I can do? I.e. camsfts stroker kits..etc?
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