What sensors would affect gas mileage? As well as not throwing a code.

And the only running problem is a minor lack of power.

Anything else that would cause bad MPG, without giving any clues such as wierd guages, noise, or a check engine light?

All the usual that anyone would expect has been replaced that usualy pertains to MPG, and I have been using shell gas for the past three tanks.

13mpg is not correct.

 

sticky injector..vacume leak.. dirty air cleaner.. dirty throttle body.... o2 sensor...timingchain wore... week compresion... burnt valve... pluged cat... there are alot of things that can effect it...

 

i would check out your o2 sensor. that would make your engine run realy funky and get you bad gas milage

 

I have ran injector cleaner as well as seafoam through the engine, new air cleaner, TB was cleaned and seafoamed, both 02 sensors replaced, new cat.

Now a worn timing chain, weak compression, and burnt valve are all new to me. I will have to look them up.

 

ya get a compresion tester and test each cylinder, not sure what psi they should be at. mayby someone else here or google can let you know what psi each cylinder should have.

 

isnt it at least 150 psi? i think so

 

140+ psi not more then 10% differance..

 

Sounds like a good start. How much should the took cost me, and any good write ups?

Thanks guys

 

you can probly rent one from an auto parts store, or you can go out and buy one they are from like 20$ for a cheap one or up to $150 and up for a snap on or mac one. and all you have to do, is take out a spark plug screw in the tester and than turn over the motor a couple times. than go to the next cylinder. it is very easy to do.

 

The factory spec is 120-150PSI.
Remove all sparkplugs.
Install tester.
The engine should be cranked for 3 revolutions, then read the gauge.
Move on to the next cylinder.

A failed sensor that causes a reduction in performance/MPG is going to throw an error code. No if's, and's, or but's.

A thorough cleaning of your throttle body, a can of Sea-Foam, a new/clean air filter, and an inspection of the spark plugs should be done before anything else.

 

How are the engine grounds? Coil packs are cheap too....

 

*2 on the coil packs.

 

All been completed unfortunatly. Even bought a performance drop in air cleaner for the hell of it.

I do notice that sometime the engine sounds louder and rougher, and other times it runs quite and smooth. However, no start up problems, missing, or anything like that.

Actually how would you know if an engine is missing? I figured I could hear it, and haven't.

I have a 2000, so there isn't a coil pack as far as I know, correct?

 

you would feel if it was missing, it would be rough idling

 

Did you ever figure out what was wrong? I am experiencing the exact same problems in my 2000 jeep cherokee. It sometimes runs nice and smooth, and sometimes it seems really loud. There is a general lack of power, and my gas mileage has dropped from 17 to 12.