Hi all,
Had my 97 Auto Cherokee sport for bout year and half. Always had bad mileage and rough idle, but not my DD so didn't mind. Over the summer, for whatever reason, starting running a bit smoother and mileage jumped up to 16-18mpg opposed to the usual 10mpg. That gave me some faith in my lil cherokee and i think i wanna purse a fix for the issue. Now im back to normal-bad mileage, misfire, even seems to "buck" a bit while driving. PA state inspection next month, gonna have mechanic tackle this misfire issue in hopes of better mileage consistently.

Thinking more of an injector issue due to the "bucking" i'm experiencing while accelerating. When it bucks i mash the gas pedal and off it goes no problem. Soon as i come to stop-spit and sputter. Don't want my mechanic to start throwing parts on it to no avail-that gets pricey.

Any thoughts would be great, i'd love to drive my jeep all winter without wanting to smash it.

 

any codes?

 

1. Yes, gotta check for any "stored" codes, even if the check engine light is not currently on.OBDII is certainly not perfect and is subject to some interpretation, but it is awfully darn good at pointing you to an offending circuit.

2. Next question is tuneup hardware. Unless you have fresh plugs in there gapped to .035 (Champion are my favorites for the 97), newer plug wires, distributor cap and rotor, you can't look to more complex possibilities.

 

Yes, have the codes written down somewhere. They were "cyl 1 misfire" and "cyl 3 misfire". Did a scan a different day and got "cyl 1 misfire" and "cyl 5 misfire". So it seems to not be a specific cylinder.

When purchased, former owners had tune up w/ receipts done at thier local mechanic 6 months prior. Took to my mechanic immediately after purchase for body work and brakes-he inspected the plug/wires/cap/rotor to also diagnose the rough idle (at which time i wasn't too worried about). He said everything did indeed look good and newly installed. BUT i can't completely say the plugs are gapped correctly as i did not install them nor did my trusted mechanic. I have been thinking of doing a re-tuneup to make myself feel better but i'd hate to replace parts that may be working fine....at least it wouldn't be horribly expensive....

 

would also like to mention: had new exhaust installed few months ago, everything from the header back w/ new O2 sensors. I can rule out the O2 sensors, and the header is in good shape-no leaks or cracks.

 

One of the first things that needs to be done for floating misfires is to verify fuel pressure. Must be done with a gauge; no shortcuts. This gauge can be rented from many parts stores.

For a 97, you should have 49 psi at idle, plus or minus 5 psi.

Not saying that is what it is, but I am saying that verifying this early in the process is a wise thing to do.