My xj has had a couple misfires since I got it. Discovered the head was cracked, changed it. With the head it got new plugs and wires. Then swapped the cap and rotor for another used one. Changed injectors and fuel rail for another used one. That helped and made it run better. So I determined that the main problem was the injectors. Ordered new ones, installed them. It stopped misfiring for a day and then resumed. Only now it's hard to start. It'll turn over several times before it catches and starts. Codes are showing misfires on 1 and 4.

 

***Do you know the "history" of this XJ? If the head was cracked and it was driven for a while, the coolant that mixed with the oil because of the cracked head can damage the engine bearings.

***Are the only codes P0301 and P0304?

***Where did you buy the fuel injectors?

1. Gotta get a new cap/rotor in there. Used tuneup hardware gets in the way of troubleshooting. Don't want to be chasing your tail for $20 in parts.

2. Fuel pressure testing. Gotta do it and has to be with a gauge; they can be rented from some parts stores if you don't have one. With a 97, you should have 49 psi, plus or minus 5 psi. It's one of the first thing any tech would check. That hard start can be related to the fuel pump. There are 2 check valves in the fuel pump assembly that can fail, leading to long cranking time on cold starts. Does it start poorly when cold, when hot, or both?

3. Compression is up next. Spec for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders. This head crack raises questions as to whether you have bottom end engine problems.

Good luck and keep us updated!

 

Not sure on it's history before the head cracking other than it has been taken off before .wrong type of gasket was used evidently and they had scored the head pretty bad somehow. Oil was not milky at all. I may have cracked it when the freeze plug blew and it overheated a bit.

injectors were bought off Amazon.
Nss was also changed at the same time as injectors.

Plug 4 looks as though there's very little fuel hitting it.

Also i don't feel it missing unless it's idling, if throttle is open at all it runs smoothly.

Would it be worthwhile to change fuel filter preemptively?

I'll be getting fuel pressure and compression checked asap

Note that as of now this is our only vehicle as my xk decided to sling a wristpin through the block

Codes are:
P1899 manufacturer control
P0700 transmission control system (MIL request)
P0300 random/ multiple misfire
P0301 cylinder 1 misfire
P0304 cylinder 4 misfire
P0705 transmission range sensor A circuit

**codes have been cleared since injectors and nss**

 

I would put my my best bet and say this is an electrical problem. Random cylinder misfire like that usually means somethings messing with the computer. Check the wiring nearby those sensors, there could very likely be exposed wiring creating a short somewhere. Mine was doing the same misfire only at idle thing, and somewhere in between changing my coil rail (00 XJ) and fixing a shorted wire at the oil pressure sensor I fixed it.

 

I've looked a bit at various wires but didn't see anything .I look deeper though. I do know at one point there was a fire under the hood by the black spot under the hood and a bit of melted plastic ( oil cap and trottle body) so a melted wire isn't farfetched.

 

Did you re-replace the cap and rotor with new equipment?
What is the fuel pressure at the rail? If there is a problem at idle I always like to spray carburetor/throttle body cleaner around and in the throttle body to allow the butterfly valve to seat well, remove gunk, and allow the valve to turn more easily.

When you replaced the spark plugs did you feel by hand for washer engagement or did you use a torque wrench?

Also, replacing the cap, rotor, wires, and plugs is almost a complete tune-up. You might as well change the filter for air, oil, and motor oil.

 

Just checked the fuel pressure. 49 lbs
and bought new cap and rotor. No change.
Oil changed last week. Air filter was still clean.

It's still hard to start and still misfiring. I'll rescan it for codes in a bit.

 

Measure the resistances in each spark plugs wire and chart them. Let's see whether there is a difference in resistivity. Do you have a manual? You can try to test the coil as well.

 

I assume that I need a properly functioning multimeter to test that

 

Yes. The Lowe end, Chinese ones found everywhere are cheap as hell, though.

 

Pressure at fuel rail showed 49 psi

swapped plug and wire from 3 and 4 to see if misfire followed. It didn't.

Unplugged injector 4 while running. Engine did not change.

Didn't see any broken wires

Haven't been able to do a compression test on 4 yet

My multimeter isn't functioning properly. Getting another soon.

Still hard to start though. Fuel related? It wasn't hard to start before the new injectors and nss. I plan on pulling my fuel rail and checking for blovkages with an air compressor.

I cleared all codes and let it idle after screwing with the fuel injector plug. The only code that showed up was p0304. That may change as I drive.

 

Can you swap in one of the old injectors on 4 and see if anything changes?

 

Yesterday I posted that I had swapped plugs and wires and it still showed a misfire on 4..
today I can still hear and feel it missing but now I'm not getting any misfire codes. Only p1899 p0705 and p0700
Wth?

 

The suggestion about swapping the fuel injector on 4 ( the troubling cylinder) was a good idea. If swapping things on the sparking end doesn't effect the condition, and unplugging the fuel injector doesn't effect anything then your fuel injector may be bunk.
Try placing an old injector in 4 and leave the rest. What are the results of that test?

 

Final update: I went to pull the fuel rail yesterday. Unbolted it, moved throttle cables, and gave a slight tug on the rail. #4 started spraying fuel .I thought I had a blockage before as I'd drained the rail already. Then I started to look and I saw the problem.... The injector wasn't in the rail .it was still in engine. With the clip still on it... Any way, I bought new plugs again yesterday too and reseated the injector and she's running 100x better.

But still hard to start
But that's for another post