ChadHubbard

I have a 2008 Wrangler X. 6 speed manual, 116,000 miles. Recently started throwing a P0303 code. I took compression readings on all the cylinders and replaced the plugs. No joy, erased the code and it came back. My compression readings were: Drivers side of engine, front to back: 160 psi, 175 psi, 175 psi. Passenger side of engine, front to back: 160 psi, 135 psi, 140 psi.

Is the differential of cylinder pressures a likely/probably cause of theP0303 code? Will the lifetime powertrain warranty cover this repair based on the values above?

thanks for any input/response.

Jay2013jk

Fuel delivery errors Your cylinder may also be misfiring because it isn't getting enough fuel to burn. The spark plug may be igniting just fine and there may be enough air in the cylinder, but there may just not be an adequate amount of fuel. This could be caused by: Bad fuel injectors or fuel pumps.
https://www.wranglerforum.com/thread...sfire.2436310/

Now read the powertrain warranty coverage details and what is covered. IMO go and ask the dealer service mgr with these readings.. Be ready they must conduct their own tests to comply with warranty requirements; cannot accept independent or DIY test results.

ChadHubbard

Thank you for your reply. I installed in plug wires yesterday, Jeep is running fine - after a few starts/miles the check engine light went off,.

I realize the dealer will need to verify my compression readings. I have a service event scheduled at the dealer on 10 Sep. Don't know if they will troubleshoot the cylinder compression if the check engine light stays off. If not, I suppose there suppose there will be enough progressive damage at some to make troubleshooting easy!

Jay2013jk

Good news.. the drivers side is within the 10% spec. Passenger lowest would be 144.. The possible culprits: Valves leaking.. Rings. Head Gasket. Do the normal check for Head Gasket blown with out pulling the head. Valve Leak down test could be done too. Wet / Dry Ring compression test (squirt oil in the cylinder and do the compression test again on the passenger side. Look all these on youtube for more detail info.
Frankly if the CEL stays off and your ride is running good, I would consider not keeping the service appt and just drive and keep an eye open.