1984 CJ running rough

[eaglescout526]

I know, not MJ but I need some help and schooling. 

 

Guy local is having some issues with his CJ. It has a Mopar injection kit with the 4.2Litre. I believe these to basically be HO injection systems and not Renix. I know a little bit about HOs, but not enough and I want to help this guy out as theres not many mechanics in the state to get this system running right.

 

So when cold, it runs rough, almost undrivable and owner feels like he is hurting it. Gets warm, little more drivable but still an issue.

He had an issue with cylinder 6 injector and had it replaced. Was a little better. Then replaced thermostat, cap, rotor, not sure if the plugs were but he said a basic tune up was performed and it helped run better but not to where the issue has gone away. What sensor could be doing this? 91-92 owners have any thought?

 

Any thoughts or ideas? Maybe any tools or knowledge and literature will help me greatly.

 

@89 MJ, 4.2Litres do not have adjustable valves correct?

[89 MJ]

Correct, the valves are not adjustable on the 258s. 
 

Does the computer control the timing too?

[Eagle_SX4]

I built the junkyard version of that conversion to run in my Eagle. It is all based on the 95 4.0 injection.

 

Maybe check the map sensor sometimes they go bad. 

[eaglescout526]

2 minutes ago, Eagle_SX4 said:

Maybe check the map sensor sometimes they go bad. 

This was something I did bring up to the owner, he did rebuttal with it should affect the engine and not just cyl 6 when unplugging the injector. But again, HO's are new-ish to me, I cant imagine the theory of operation being drastically different from Renix 4.0.

Owner could be right about that, You and I could be right about the MAP. I will see this CJ in person this weekend.

 

I did leave out a detail, the engine was swapped with another engine that has this injection set up. Something about the original block being cracked and the head was swapped to the doner engine.

 

Let me ask ya Eagle, since this is HO, how could we check to see if it has any codes? Scan tool or would I be able to rig up some sort of light? 

[Eagle_SX4]

1 minute ago, eaglescout526 said:

 

Let me ask ya Eagle, since this is HO, how could we check to see if it has any codes? Scan tool or would I be able to rig up some sort of light? 

If this was indeed the Mopar kit it should have a check engine light somewhere. The codes are just a series of blinks and pauses. This thread shows how to read them.

 

 

 

[eaglescout526]

24 minutes ago, Eagle_SX4 said:

If this was indeed the Mopar kit it should have a check engine light somewhere.

This is what I’m hoping for. 
Will a multimeter help me out for diagnosing his issues? 

[Eagle_SX4]

5 hours ago, eaglescout526 said:

This is what I’m hoping for. 
Will a multimeter help me out for diagnosing his issues? 

Yes it could but unlike the Renix system I haven't been able to find much info out there for testing all the components. Most of the time the fault codes will point you in the right direction.

[Eagle_SX4]

I found the instructions for the kit. Oddly they are on Quadratec's website. https://www.quadratec.com/sites/default/files/installation_instructions/2688.pdf

[Eagle_SX4]

The check engine light info starts on the bottom of page 13.

[eaglescout526]

1 hour ago, Eagle_SX4 said:

I found the instructions for the kit. Oddly they are on Quadratec's website. https://www.quadratec.com/sites/default/files/installation_instructions/2688.pdf

What an odd place to find the instructions! Thanks Eagle!