OK guys long time looker finally joined when I picked up my 96 xj. Now I knew it needed a few odds and ends when I bought it from my buddy but he lied to me about a lot of it and now I'm just trying to get this thing right so here's where I sit.

Engine missing on cylinder 1 and 3
I've replace
Distributor
Cap
Rotor
Plugs
Wires
Pcm
Cleaned throttle body
Cam position sensor

It runs really rough on idle and I can hear it miss when rpm is increased.

At idle I pull the injector harness for cyld 1 and 3 with no change to how it runs.
Test injector plug it's getting power and ground
I swapped injectors around problem stayed at 1 and 3
I swapped spark plugs around problem stayed at 1 and 3
I've tested for spark it's good
And tested injector it sprayed with power was applied
(Has upgraded 4 hole injectors)

Going to do a compression test tomorrow looking like this thing is burnt up

As of right now I'm really to kill my (used to be) friend. Live and learn just hoping somebody can shed some light on something I might be missing

Thanks guys

 

Welcome to the forum. Was the computer reset when the injectors were installed?

 

Thanks glad to be here and not that I know of. I pulled one off another 96 at the junk yard today installed and same problems

 

May be a long shot but its worth a try. Take off your battery cables for about 10 minutes and put them back on. I only take mine off for about a minute but some say longer. That will reset your computer.

 

wile doing the compression test you should also do a leak down test. you could have burned up rings in 1 and 3 or a valve could be sticking. pull the valve cover again and run the engine with the cover off. see if the intake or exhaust valves are sticking causing the miss fire. you ruled out the electrical and fuel related possibilities now you have to look for a mechanical issue.

 

Honestly if the compression test yields bad I'm probably gonna go ahead and rebuild it at least new rings and get the head worked

 

Compression test is definitely the next step.

Let us know the specific compression results for each cylinder.

The spec for the 4.0 is 120-150 with not more than a 30 psi variation between cylinders.

 

Update. Pulled valve cover this morning really hoping to find a loose broken rocker no such luck. Last night when I pulled the injectors number 1 and 3 had brown tips all the others are still clear and brand new looking. Starting to think intake valves aren't seating well see what the compression test says

Edit. Is an in frame possible on the 4.0? Can the Pistons be removed as an assemble through the bottom oil pan area? I'd prefer not to pull the engine if possible

 

Update. Pulled valve cover this morning really hoping to find a loose broken rocker no such luck. Last night when I pulled the injectors number 1 and 3 had brown tips all the others are still clear and brand new looking. Starting to think intake valves aren't seating well see what the compression test says

 

Just to be double sure, ya know, The books and diagrams are wrong! #1 is at 5:00, viewed from the side. 153624 clockwise.

More than once I've found swapping the two missing wires solved the miss. (some V8's are not so easy to trace)

 

I don't have a book I actually followed the firing order stamped on the intake. I got this thing on Saturday granted my no longer friend lied about a lot of it but I don't think he knew it was this bad

 

Compression test results
Cyl 1 45 psi
Cyl 2 165
Cyl 3 40
Cyl 4 180
Cyl 5 120
Cyl 6 180

Looks like the head is coming off tonight

At least like this it sounds like it's got a huge cam on it lol

 

Could be Valves messed up causing the loss of compression

 

Pulled the head and I have to say that was the easiest head I've ever pulled. Anyways intake valve on number 1 and number 3 are not seating fully can see light coming through when I put my flash light in the port. Dropped it off at the machine shop with the intake gonna get cleaned and worked. Anything I should do while I'm this far in? I'm replacing lifters and some old sensors but everything else is pretty straight forward

Thanks guys

 

It's so nice when people follow the order of operations for diagnosing a problem, and find the problem. Cheers for getting at it yourself.