XJ_Cherokee_99

Hey my cherokee has been starting up very weak lately. it turns over 1st try but for a few seconds it runs as if its not getting enough fuel and seems bogged down. after that it runs perfect. It runs bad for 3 or 4 seconds then the exhaust and engine gets louder and runs better (normal). Let me know if you have any idea what this might be. I haven't replaced any parts recently and nothing has been changed.

tjwalker

Your symptoms could be related to a "leaky fuel injector". That injector could slowly be leaking raw fuel into that cylinder. A leaky injector also reduces fuel pressure. So when you try to start it, it takes a little extra time to build up the required fuel pressure, then a few moments of running "rough" until the leaked raw fuel is burned off.

Best way to isolate this is with some "comprehensive" fuel pressure testing. Going to need a fuel pressure gauge for that, they can often be rented very inexpensively at your local parts store if you don't have access to one. Or you could try pulling a spark plug out before a cold start and see if you find one that is wet with fuel. How many miles on your engine and fuel injectors?

There are other possibilities but this is where I would start. Good luck and keep us updated!

XJ_Cherokee_99

Thanks this is very helpful. I have 237000km (147xxxmi) on the stock injectors. I was thinking of doing the injectors swap everyone has done to their XJ's so i could start there and see if it makes a difference. I am also getting really poor gas mileage. Around 13mpg. could this be related?

evil_goat

It is probably related, although there are a ton of things that can fail and affect gas milage.

Idunno

You've ruled out a fuel leak? I'm seeing most people get around 16 to 18 MPG. What was yours before the problem? An unexplained loss of 3-5 gallons per miles is huge so you're either leaking externally, or otherwise, and your exhaust has got to smell very rich with a poor idle and above (your "bogged down" could be flooding). Do you smell raw fuel at the tail pipe? Seems to me you chould have an O2 sensor throwing a code at you as well. Is your CEL working?

XJ_Cherokee_99

I haven't ruled out a fuel leak completely but it would either be at the injectors (wouldn't be that bad mpg decrease) or the tank. theres no spills ever so if there is a leak it would just be evaporating. my cel is not on but maybe the bulb is out? I've owned my jeep for a year now and it was about 15-16 mpg but is now 13ish which seems worse. the exhaust does smell like something unlike the newer cars but i don't really know if its what your talking about. I've also read that a bit of black at the tailpipe could be unburnt fuel (running rich)

cruiser54

Winter fuel blend and cold temps can trash your MPG.

How many miles on the plugs, wires, cap and rotor?
Ever clean the throttle body?

XJ_Cherokee_99

wire cap and rotor were replaced 1 1/2 years ago and I relaced the plugs 6 moths ago. the guy said he cleaned the throttle body and IAC.

cruiser54

I'd clean the throttle body and IAC if it were mine.

XJ_Cherokee_99

ok I'll do that

cruiser54

Here's something else you oughta do: http://cruiser54.com/?p=35

XJ_Cherokee_99

Ok so i cleaned the throttle body and IAC and it wasn't too dirty. also the electrical connections on there were perfectly fine. I haven't checked all connections yet but the ones to the TB are fine. I recently changed the battery terminals since the old ones were pretty messed up. When i did that the jeep started up perfectly fine. then after 3 starts or so it went back to the weak startup. when I changed the terminals something must have reset because my radio went back to the stock date and time. So I detached the wires from the battery and held them together (replicating what may have happened when changing the terminals) and then it started up fine again. what could this be?

cpttuna

i WOULD REPLACE THE CAP AND ROTOR AND IAC

Frostthegreat

What’s the engine temp at?

XJ_Cherokee_99

normal temps. always just under 100 degrees C