Evolution860

So I just bought a new-to-me 96 Cherokee XJ. I keep getting these p0300 and p0301 codes. I have installed


Plugs
Wires
Distributor cap and rotor


Have also checked for vacuum leaks and haven't found any.


Compression test shows:


Cylinder 1 -120
Cylinder 2 -110
Cylinder 3 -110
Cylinder 4 -135
Cylinder 5 -135
Cylinder 6 -120


I also noticed that some of the cylinders were more difficult for me to get a tight fit on the compression tester, those cylinders were also the ones with the lowest score. I'm thinking since I couldn't get a tight fit on those cylinders, some pressure was escaping.


Also did a fuel pressure test that read 45 pounds of pressure.


Any ideas where to go from here?

Grip

Have you searched P0301?

Tons of info

Evolution860

Yes, I have searched it, Cylinder 1 misfire. Since I'm new to this vehicle, I'm wondering if this is something that can be fixed relatively easy. As you can see, I have been narrowing down possibilities since the code appeared

Grip

You should also see multiple fix's or things you can do to narrow down what needs to be fixed.

Evolution860

And that's what I've been doing, I know some cars have certain gremlins that happens all the time and sometimes its the easiest little fix possible, just was wondering if I was overlooking anything.

Grip

What about the cylinder 1 injector?

Evolution860

I threw some injector cleaner in the gas tank, hopefully if its clogged, that will help, if the code pops up again, Ill swap with injector 2 and see what happens. checked the fuel pressure and its about 45, so I know the issue isn't the fuel pump.

Evolution860

I've been doing 1 thing at a time, everytime I been clearing the CEL and running it

Grip

Dont waste time with injector cleaner. Swap the injector.

If it becomes P0302, you need in injector.

Might as well buy the upgraded 703 injectors since all 6 are cheap.

Grip

Have you looked into a CPS?

Evolution860

Do the 703 add any HP? or Gas mileage? And CPS, along with the Injector is my next thing to test..

Grip

Research 703 injector info.

If you buy a CPS, buy a Mopar one. The aftermarket ones from parts stores last about a year.

Evolution860

You think a Napa carries the Mopar CPS?

Grip

No. Mopar is chrysler.

Jessejeep27

Hello, I've read these posts. Any thoughts on a 2001 Grand Cherokee also getting misfire codes? I'm getting 0302. and 0301.

I have replaced spark plugs. 6 month old plugs a lot of carbon.
Tested the voltage to each injector.
Did the Noids test, pulsating light.
All checked out to my manuals specs.

Compression test done and good.

Would you suggest replace fuel injectors (1 and 2) on my year Jeep as well?