Missing goes away when warm

[89 MJ]

My truck misses. Sometimes. It misses until it gets warm. Any ideas ? Thanks

[Eagle]

How old are your spark plug wires?

 

[89 MJ]

Just now, Eagle said:

How old are your spark plug wires?

 

I am not sure, but unplugging them one at a time rarely makes a difference. Thanks

[Warren Mohler]

if it's in the morning and possible dampness involved inspect cap and rotor, if all looks good spray some water around cap and wires with engine running to see if there is any spark jumping

[89 MJ]

8 minutes ago, Warren Mohler said:

if it's in the morning and possible dampness involved inspect cap and rotor, if all looks good spray some water around cap and wires with engine running to see if there is any spark jumping

Will do, thanks!

[Gt-401]

That happens to me once on a 91 Cherokee I had awhile back. It got so bad that I would have to start it. Then it would die after a few seconds. And I would have to start it over and over again till the engine got warm. Then it would run fine. I finally chased it down to a bad cam sensor in the distributor. Once I replaced it it ran fine.


Sent from my iPad using Tapatalk

[89 MJ]

18 minutes ago, Gt-401 said:

That happens to me once on a 91 Cherokee I had awhile back. It got so bad that I would have to start it. Then it would die after a few seconds. And I would have to start it over and over again till the engine got warm. Then it would run fine. I finally chased it down to a bad cam sensor in the distributor. Once I replaced it it ran fine.


Sent from my iPad using Tapatalk

Noted! I appreciate it!

[Andy in Pa]

Sounds like a moisture thing.  The coil mounts to a distribution block that is potted on the bottom.  That potting cracks with age and allows moisture in, causing everything from misses like this to complete no-start conditions.  Had one fail in my 87 MJ.  Was wondering why it was acting finicky for a few months, then it completely failed and I figured it out.

[89 MJ]

2 hours ago, Andy in Pa said:

Sounds like a moisture thing.  The coil mounts to a distribution block that is potted on the bottom.  That potting cracks with age and allows moisture in, causing everything from misses like this to complete no-start conditions.  Had one fail in my 87 MJ.  Was wondering why it was acting finicky for a few months, then it completely failed and I figured it out.

How much did it cost to fix?

[JMO413]

https://www.oreillyauto.com/detail/b/import-direct-ignition-4488/ignition---tune-up-16776/ignition-module-control-unit-ignitor-12521/e281cd9fff15/import-direct-5-terminal-ignition-control-module/140197/4575249

This is the link to the one I bought from O'Reilly's. We have had good luck with import direct parts at work. I replaced mine beacuse the bottom was cracking like Andy was describing. Mine finally gave up when I soaked it flushing the heater core.

[89 MJ]

21 minutes ago, JMO413 said:

https://www.oreillyauto.com/detail/b/import-direct-ignition-4488/ignition---tune-up-16776/ignition-module-control-unit-ignitor-12521/e281cd9fff15/import-direct-5-terminal-ignition-control-module/140197/4575249

This is the link to the one I bought from O'Reilly's. We have had good luck with import direct parts at work. I replaced mine beacuse the bottom was cracking like Andy was describing. Mine finally gave up when I soaked it flushing the heater core.

[Andy in Pa]

1 hour ago, JMO413 said:

https://www.oreillyauto.com/detail/b/import-direct-ignition-4488/ignition---tune-up-16776/ignition-module-control-unit-ignitor-12521/e281cd9fff15/import-direct-5-terminal-ignition-control-module/140197/4575249

This is the link to the one I bought from O'Reilly's. We have had good luck with import direct parts at work. I replaced mine beacuse the bottom was cracking like Andy was describing. Mine finally gave up when I soaked it flushing the heater core.

Yep that's the one.

 

A.

[89 MJ]

Thanks guys. I think I might just go a different route seeing as though it misses, knocks, and needs a rear main seal.