Troy Healey

2000 xj, sometimes starts and runs fine, sometimes runs rough and miss fires and will sneeze out of the intake. So far the crank sensor has been replaced, cam sensor has been replaced, fuel pump, air idle control valve, injectors removed and cleaned up(video posted was before cleaning). Removed coil rail and tested all 6 cylinder for spark when cranking. Throttle position sensor tested from battery ground to signal wire 5vdc. Signal wire to ground .3vdc to 4.8 WOT.smooth voltage increase when opening throttle. any further recommendations? Ran fine when I purchased it a month ago and has progressively gotten worse. Fuel tank has been dropped pumped out and cleaned with fresh fuel added and some sea foam treatment.
Edit: spark plugs have been replaced with double platinum champion plugs and no vacuum leaks(checked with starting fluid around all hoses and gaskets)

Ralph77

What plugs were in it before you replace them?
I will only use Champion Copper Tops in my '00.
438's.

Troy Healey

I believe copper tops but it was still having the hard start issue and the plugs were extremely beat

Ralph77

Now that is what I kinda figured you were going to say.
IMO those fancy plugs do not belong in an XJ.
If this were me I would go back to some Copper Tops, new, and see what happens.

tjwalker

Have you tested your fuel pressure with a fuel pressure gauge? Saw that you cleaned it but pressure needs to be verified with a gauge. Spec for the 2000 is 49.2 psi, plus or minus 5 psi. Needs to be ruled in or out....

Dave51

Check compression and manifold pressure to confirm no intake leaks or clogged exhaust.

cpttuna

replace BAT + to starter cable and all grounds

Roler

Could even be as simple as a loose bolt on a ground, connection or cable..

- And brand of CPS replacement?

- when you say "sometimes runs rough", is that on start up only or also whilst driving?

Jim Malcolm

https://www.cherokeeforum.com/f67/va...m-foil-265302/

Investing in the insulation, in addition to the above trick, may be worthwhile if your OEM insulation is missing...

Troy Healey

just replaced with champion copper tops same issues

Troy Healey

will miss fire if I give any gas and rough idle. Then at times runs perfectly

Troy Healey

has 55psi

Troy Healey

was napa brand, when plugging in my scanner I’m getting crank readings from sensor when turning over

Troy Healey

I don’t have any way to check manifold pressure

Troy Healey

there is no insulation on mine at all, what would be the best way to check if it’s vapor lock?