What do you think? NGK?

 

I'd seek out an OEM ignition coil for a stock 4.0 liter engine, stay away from the "el-cheapos". I believe NGK would fall into that category and I am a big fan of the NGK brand.

I recommend against the advertised "high performance" coils. The 4.0 engine is actually fairly low tech and an OEM coil is not only more than enough to do the job, it is going to be more reliable.

 

I'd get one off an SRT V-10 motor... probably add about 10-15HP....

 

Buyer beware of new parts … There just might possibly be a solution to the 97 mystery! Our mechanic and his father made a house/ranch call today and they may have discovered the problem. First of all for some reason the old 1986 coil once again began working which totally mystified them. The new OEM MOPAR still wouldn’t work. In further tests the 86 coil stopped working! The new replacement connector from Summit was taken apart and it was discovered that the female ground cavity the coil pin plugged into was pulled back almost a 1/4” . Upon closer examination it was decided that the 1986 coil’s pins appeared to be a little thicker and possibly a tad longer. That may have made the difference to allow the 86 coil to make contact where as the newer coils couldn’t make contact. Now it is a matter of trying to find a better replacement connector for the coil. Right now, today, we have the coil zip tied together to hold the connector tight to keep the connection until a permanent fix can be made. But at least we can drive our vehicle again.

The new connector was installed when the OEM connector was discovered to cause stalling when it was wiggled. The OEM connector probably was the cause of the intermittent stalling and when the new connector was installed then the coil was not able to make contact and fire the engine.

I want to thank everyone for your time and suggestions for testing the mystery. I will endeavor to come back in a month or so and give a final update hopefully with no further issues. It is frustrating when one buys a new part only to latter find out the new part ended up creating a problem. Many thanks again.

 

Wow! One of the longest threads in forum history! My primary coil connector was loose on the pins , and was causing problems random cutting out etc? I removed coil, soldered two matching wires to the pins then used the good ol chocolate connector and connected to the harness ? Leave one wire longer on each side then one connector will sit nicely behind the other cover with silicone and then new split conduit? I was lucky finding problem when changing coils like OP did over and over!
You need to lengthen wires as harness is only couple of inches going to the coil

 

Country of origin is a huge factor when choosing new parts.

 

Thank you! My new coil was 80 dollars aust, and a supposedly reputable supplier in country.however its ohm reading was half of my old one so I put it back on and improved primary connection
Now I am stuck with a coil and cam sensor that I cant return as taken
too long to find out both were not up to spec? More important my xj is running again!!