Help With a 2000 Cherokee 4.0: Horrible Mileage and Labored Starting...

[GJStringert]

Nix The Aforementioned Injector Repair...

So I have a plot twist for you all: the injectors have never even been touched, we were talking over dinner tonight and she had no idea what I was talking about when she read through my posts from earlier, so I guess I imagined that. Honestly I don't know where that came from, maybe talking to my buddy Ben with the identical Jeep?? Yikes I'm 21 and loosing my mind... Jeez sorry to waste time on that haha!

Ok so now it looks like we'll throw some new injectors at it, I've got time Thursday and I think I can slam through that real fast, hopefully something fuel mileage-wise gets remedied so she's not $300 deep in fuel expense by the time she gets home for spring break!

The more I think about it then, the more a plugged cat sounds realistic. I know, at least on my friend's 6.0 Powerstroke, early on when he was dropping injectors (before we found out about the 6.0 fixes...) he was really worried about them gumming up his cat, EGR, etc, so I'll give the cat a look anyway.

MoGas, good call, "labored" probably isn't the best word to use there. It spins at a normal speed, just takes longer to start, it doesn't struggle at all. I'll post a video as soon as I can get one/find one on Youtube that's similar.

FredB, air pressure is good all around, and it hasn't been in 4WD in months (poor Jeep huh?). I had the whole thing on jackstands a few weeks ago and went around and manually rolled the wheels to make sure a brake wasn't seized or anything, so on the topic of rolling resistance, I think we're good to go!

Well expo folks I feel real bad now, I wouldn't have wasted your time with all that if I hadn't convinced myself the injectors were good (I still don't know where THAT came from...). But as always I appreciate the replies and help, I'll let you know (hopefully Thursday night) if a new set gets us going!

 

[mudbutt]

Yeah, my first thought was leaky injectors too. If you are still stumped, there is a lot of info on NAXJA.

 

[redveloce]

+1 on the injectors. That's the one place where the starting and mileage issues would seem to cross over.

 

[Dan Grec]

Something else random to check is stuck calipers/drums causing excessive rolling resistance.

I just read about it happening to someone on another forum and it was killing mileage.

-Dan

 

[GJStringert]

OK folks I just got done throwing a new set of injectors in. I still can't believe this but the starting issue was solved right away ( I would have thought that would have taken a little while, to work out air in the lines, etc...) . visibly, all but 2 of the injectors seemed to be in good shape. The 2 closest to the firewall had a lot of grimy crud built up, maybe that was causing problems? Anyway now we'll have to run a tank or two through it and see what the mileage is like, for now we play the waiting game...

Otherwise thanks a lot for the help! Ill check back in after a tank of gas or two.

 

[1stDeuce]

Sounds like you may have had a stuck injector. (Or two...) The rear two injectors see more of the oily crap that the PCV system adds to intake air, but not that much... They also are exposed to anything that gets sucked out of the vacuum booster... It's not using brake fluid is it?

Hopefully the injectors were it. Your fuel filter is not really servicable. It's part of the fuel module though, so if you replaced the whole sender instead of just the pump, it's new anyway.

If you did have a stuck injector, you probably will have issues with the cat sooner or later... If there's not emissions test in your area, just hollow it out. My '98 TJ passes emissions just fine with no cat at all. (There's a resonator in it's place, so they don't know the difference...)

EDIT - I see you're in Colorado. That's where my TJ passes with flying colors and no cat.

 

[GJStringert]

Brake fluid's good, haha that's one of the few fluids that DOESN'T leak! For sure my next project is going to be tracking down the source of all her oil leaks, leaks at the pan, valve cover, crank case, EVERYWHERE. Fortunately, for the time being, it leaks so slowly that we don't have to worry about it. I just keep telling her to get it through college (we have one more year), then when I can build the garage of my dreams we'll park it for a while and pull everything out (I'm feeling a supercharger, some tranny work and a 4 speed Atlas...). Of course that's in a perfect world!

I can't, for the life of me, figure out the regulations on smogging in CO. When I bought my Cummins last summer they had to get it smogged so I could plate it (but I plated it in Colorado Springs, and I live in Greeley fulltime, for now that is), and I've heard Weld county doesn't bother with emissions. I should really figure that out, I have no cat or muffler on my 12 valve (and it's my DD/ do all truck), AND the exhaust dumps before the rear tire. I'll be deaf soon if I don't dynamat it or put a muffler on... It does sound mean though!

Thanks for checking in!