highaltitudeXJ

Hey all, my first post on the forum! I have a 1999 XJ I have been working on. I have a weird issue that I cannot troubleshoot.

when I start the jeep and get driving there’s a weird engine lag. Foot on the gas, but no power or RPM increase. Sometimes this is accompanied with a click or pop noise (engine misfire?)



my fuel pressure seems fine. I have changed some parts to try to troubleshoot this: spark plugs and harness, IAC, TPS, Ignition coil pack, removed the cold air intake the last guy put on and changed to stock.

what should I look to? Has anyone experienced a similar issue? My only other thought is that I live at 10k feet and maybe the altitude is making the fuel perform weird.

thanks any advice greatly appreciated!

boxburn

Does it act fine in Park or Neutral?

highaltitudeXJ

i have a slightly high idle in park

boxburn

How does it rev? Have you had a look at your vacuum lines, more specifically the rubber elbows for any cracks or breaks?

tjwalker

Have you actually TESTED your fuel pressure? Testing is the only way to know your fuel pressure is within spec. For a 99, you should have approx 49 psi plus or minus 5 psi. Test it if you haven't already. Most parts stores will rent you a fuel pressure gauge very inexpensively.

Any check engine light? If so, pull codes and detail them here, not a description but the actual codes. Even if the check engine light isn't currently on, I would put a code reader or scan tool and see if there are any "pending" codes, which are codes that haven't quite reached the threshold of setting a check engine light.

Good luck and keep us posted!

highaltitudeXJ

Thank you I just tested at the local auto part store 49-45 PSI even after a few minutes at idle. I ran codes on my OBD and did not find any pending or otherwise. Gonna check vacuum hoses as another user suggested then I suppose it must be injectors if that doesn’t work.

matthew gaston

I had a similar problem it was a faulty distributor sensor mines a 95 not sure if 99’s have distributor cap and rotor sensor

IJM

Disconnect the upstream O2 sensor at the connector and see if that makes it go away. If so, you've found the culprit.

highaltitudeXJ

Thanks all, after changing the ignition coil I cleared the ECU and re did some of the ignition sensors again. This seems to have mostly resolved the misfire and lack of power. Thank you for your helpful advice!

SurfcatXJ

Thanks for the update, it's useful to everyone when threads are updated with info that resolved the issue.