ecu problem -

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post #1 of 4 Old 05-12-2013, 07:56 PM Thread Starter
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ecu problem

I have a 89 jeep yj. it had a blown 2.5L in it when i got it a year ago. well in that year i have put a 4.0L from a 91 XJ into it along with the ax-15 tranny and the np-231 t case into it. i have redone all of the wiring to make it run in the front. matched up the bulk head connectors from the xj engine portion to the yj front light portion to the 89 yj bulkhead. i also put in a fuel filter and pump for a 91 yj 4.0 l new and have all of the temp and o2 sensors hooked up. I am still getting some hesitation when i punch the gas sometimes. i am wondering if there is a difference in the ECU for a 91 wrangler ECU and a 91 XJ ecu or re they set the same. i have the ecu for the 4.0L 91 XJ. do i need t get one that was out of a wrangler or do i need to get this one reprogramed or should it be fine the way it is. also could the hesitation be the catalytic converter? i know it needs replaced

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post #2 of 4 Old 05-13-2013, 07:51 AM
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1991 YJ Wrangler 
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I've been running a complete '91 XJ 4.0L/AX-15 and ECU drivetrain in my '91 Wrangler for 4 plus years without issue, I'm sure the XJ ECM will work fine. Your Cat could cause hesitation issues if it is clogged, You will usually see a decrease in power if this is the case. Going from the 2.5L to the 4.0L with the 4.10 axles, your rig should run like a scalded ape. Did you wire up the CEL lamp to work with your new set up? If so, have you checked for codes?
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post #3 of 4 Old 05-13-2013, 08:25 AM
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1989 YJ Wrangler 
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Did you setup your cel? You always need to start by checking codes. If you didnt then hook up a test light to your battery positive and the wire for the cel on pin 32 of the ecu. You should see it in the wiring diagram. It will act just like the CEL so you can use the key to check the codes.
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post #4 of 4 Old 05-13-2013, 02:11 PM Thread Starter
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did not know that about he CEL. wil do that. thank you
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