visit local part store - NAPA always my 1st choice -
well's electrics has a connector that may help - see diagram attached

 

visit local part store - NAPA always my 1st choice -
well's electrics has a connector that may help - see diagram attached

I looked into that. The only problem is, I already have the plug that fits onto the coil. The other end has been cut off. By chance do you know if the whole harness can be replaced? It leads back behind the engine and runs into a plastic conduit. Not sure where the end of it plugs into. I figure it runs into a much larger plug with other stuff, which would be a pain trying to replace the whole thing.

 

Needs some help. I just bought a 04 Grand Cherokee 4.0 with 155,000 miles. I knew when I bought it that it needed a few suspension parts, mainly shocks. It it ran good during the test drive. 3 days later I’m getting a really bad miss but it’s not all the time. Threw a random misfire code. The guy I bought it from said he put a new coil and plugs on it. So I decided to check the coil and the connector and found this. View attachment 4130990
Looks like someone tried to replace the plug and cut it to short, so it’s spliced in 2 spots. 1 end is heat shrink Ed and the other is some kind of quick connect plug. So my question is what is the best plan to repair this?

And yes, that is blue painters tape wrapped around it. Which was my 2nd clue this may be a problem. The first being the duck tape around that.

Have you checked the splices and repaired the faulty ones yet

Needs some help. I just bought a 04 Grand Cherokee 4.0 with 155,000 miles. I knew when I bought it that it needed a few suspension parts, mainly shocks. It it ran good during the test drive. 3 days later I’m getting a really bad miss but it’s not all the time. Threw a random misfire code. The guy I bought it from said he put a new coil and plugs on it. So I decided to check the coil and the connector and found this. View attachment 4130990
Looks like someone tried to replace the plug and cut it to short, so it’s spliced in 2 spots. 1 end is heat shrink Ed and the other is some kind of quick connect plug. So my question is what is the best plan to repair this?

And yes, that is blue painters tape wrapped around it. Which was my 2nd clue this may be a problem. The first being the duck tape around that.

Needs some help. I just bought a 04 Grand Cherokee 4.0 with 155,000 miles. I knew when I bought it that it needed a few suspension parts, mainly shocks. It it ran good during the test drive. 3 days later I’m getting a really bad miss but it’s not all the time. Threw a random misfire code. The guy I bought it from said he put a new coil and plugs on it. So I decided to check the coil and the connector and found this. View attachment 4130990
Looks like someone tried to replace the plug and cut it to short, so it’s spliced in 2 spots. 1 end is heat shrink Ed and the other is some kind of quick connect plug. So my question is what is the best plan to repair this?

And yes, that is blue painters tape wrapped around it. Which was my 2nd clue this may be a problem. The first being the duck tape around that.

Have you checked those splices, and repaired the faulty one(s), if any, yet Hitch?

 

The Jeep gods are not pleased with this offering. Listen to Jtec, if he has a recommendation, best bet is to follow it.

 

Which offering would "This offering" be after being then please G?

 

you are going to have to splice - thinking was a NEW connector with adequate leads to make for an easier done & cleaner looking splice. You don't a new harness.

 

Have you come across "Waterproof Solder Seal Heat Shrink Sleeve Wire Butt Terminals Connectors" in your travels JT?

If so, how do you rate them please?

 

not familiar - I am OLD SCHOOL 2nd nature using shrink tubing and soldering.

 

I haven't used them either JT.

Here's a video about them if you want to watch it.

 

Headed to my local junk yard today after work. Fingers crossed!

 

​

 

Update. So I got the wiring harness rewired. So now it only misses out under a load and it doesn’t do it all the time. But once it starts running rough it keeps doing it till I turn it off. Usually feels like it’s running on 5cyl when it happens. But shut The engine off and restart it, it runs fine again. Coil pack maybe?

 

Coil pack maybe?

That would be my first guess. I'm not much on the 4.0, but I believe the coil pack has 3 individual coils. I would not be surprised if that horrid hack job handed off to you (that picture made me cringe) had a poor connection causing an arc. An arc could indeed burn some lamination in one of those coils. A small burn or even thin spot in the lamination can short a portion or all the winding, especially when they warm up. I also don't know of the quality of the aftermarket coil packs. I'd lean towards an NGK for $100ish, but I'd also first look to a 4.0 guy for best choice.....

 

I guess the blue painters tape was a sign of things to come…..

 

Can we regroup? I am confused where we are and whhats wrong

you repaired the coil connector.
Its still running poorly -
What are you seeing as codes? post ALL of them.
runs poorly, turn off then it runs OK for a while and repeats.........

 

P0300-P0302-303-304-305

 

Wiring connector is repaired. Before the repair when it cut out it wouldn’t hardly run. Now it runs fine….till I either drive it long enough for the engine light to come on or hammer the accelerator. If I hammer it the engine light will flash. Once it starts to run like it has a miss, I can shut the engine off and restart it and it runs fine again. The engine light is on now. I’m going to get the code read after work. I can update what the code is then.

 

stop erasing codes.
Do you have a scanner capable of viewing live data?

How did plugs look - color deposits can be a clue.
All cyl's misfiring, might want to check fuel pressure - post PSI.
How ae you checking codes - it sounds like key on off trick? That may not show ALL codes.
Jeep is STOCK (engine) no modifications or aftermarket BS?

 

Engine is all stock. I’ve used a code reader and the key on/off trick, both show the same. No access to live data unfortunately. Swapped out the coil for an old one I had that was giving me a similar issue, or so I thought. Plugs look ok. I’ll post some pics.

#s 3&6 looked the same.

 

Engine is all stock. I’ve used a code reader and the key on/off trick, both show the same. No access to live data unfortunately. Swapped out the coil for an old one I had that was giving me a similar issue, or so I thought. Plugs look ok. I’ll post some pics.
View attachment 4137134
View attachment 4137135
View attachment 4137137
View attachment 4137136
#s 3&6 looked the same.

 

Update, so after swapping coil packs. This morning on my way to work the engine light came back on. The jeep is showing the same codes, P300-P302-P305. So I assume that rules out the coil. Number 2 & 5 plugs are the only two that looked different from the rest.

 

check fuel pressure post PSI.

No scanner only code reader and key on off -
TRY this free easy inexpensive - When the CEL comes on take advantage of free code scans many auto part stores do. Copy and post ALL codes they retrieve.

 

I'll swing by the parts store after work and get the codes read and grab a fuel pressure test kit. Are cylinders 2&5 are on the same timing?

 

tip - on the 4.0L paired cylinders add up to 7. so 5+2 = 7 they are paired.

KISS - PAIRED cylinders both reach TDC at same time - a cylinder is TDC compression the other is TDC exhaust.

 

Codes read the same. P300-302-305. Fuel pressure @ idle is 49. No fast drop off after engine is turned off.

 

Seems to only really miss out at 2500-3k rpm. After the CEL flashes and I let off it will miss out till I turn it off. Happened today on my way home, limped it into my garage. Messed with a few wires and connections “none of which helped”. Turned it off and back on, idles just fine. This thing is gonna make me go bald lol

 

AFTER SOME MORE READING. IS IT POSIBLE FOR THIS TO BE HEAT SOAK? THE JEEP DOES NOT HAVE THE HEAT SHIELD AROUND THE MANIFOLD ANYMORE. BUT IF THAT WAS THE CASE WHY WOULD SHUTTING IT OFF AND TURNING IT RIGHT BACK FIX IT?

 

How difficult would it for you to fit a heat shield around the manifold please Hutch?

I daresay Mopar had a good reason for fitting a heat shield round the manifold in the 1st place.

 

jeep issued a TSB for heat shielding the injectors...
GOOGLE jeep heat shield - you will find some ideas.

I'm thinking it's winter temps for most of the USA, a little to early for heat soak.