power problem

[c12mec]

Ok, this is my first post on this site so hang in there.

I have a 2001 jeep cherokee limited with the 4.0 engine, auto trans.. I have recently noticed a loss of power, especially during acceleration. My gas mileage has gone from 19-23 mpg to 16-18.5 mpg. I have notice a sandpaper type sound while the vehicle is moving but not when idle.

I have also noticed a frequent "bump" when accelerating from standing still and sometimes when stopping.

I have taken my jeep to the shop a few times and they have told me they can't find anything wrong. Computer checks good, etc.....

If anyone can help that would be great.

 

[Bounty__Hunter]

16-18 is pretty common for that drivetrain.

The bump is likely a suspension component, either a worn front track bar or control arm bushing.

If it were a sensor problem, a check engine light would come on indicating a trouble code. Without that, you're generally limited to tuneup, and maintenance troubleshooting like cleaning the throttle body and injectors.

 

[Saurian]

Hmmm... I am the owner of an '00 Cherokee Sport, 114,000 miles, 4.0, auto... I will offer what thoughts and advice I can.

Sadly, I must concur with Bounty_Hunter on the gas mileage, meaning not that I'm sad to share his opinion, but rather, tragically, that's pretty typical. Mine has a gross average right now of 15.4 MPG. That's an overall between freeway and city, gas/miles traveled, input to a spreadsheet every time I get gas. At 100,000 miles, I did the spark plugs, O2 sensors, pulled and cleaned the throttle body, transfer case and diff fluid change, oil change, air filter... The works. No effect really on the gas mileage.

As far as the loss of power goes, all the things I listed are general maintanance that are good for the Jeep... O2 sensors these days generally have a lifespan of about 100,000 miles, and don't always throw a code when they are going but not gone. Diff and transfer case, I do every year. Oil, every 3,000, air, when it needs it... I can suggest these things, might make all the difference in the world, might not do much, wish I could help you more... Another suggestion, perhaps, is the fuel filter; if the engine is starved for fuel, it'll be sluggish, especially during acceleration.

Regarding the sandpapery sound... The only thing that comes to mind is perhaps something in the brake system is sticking...

That's about all I've got, hope some of it can be of help, or at the least, do no harm And welcome to Jeepz, from one XJ owner to another...

 

[c12mec]

Thx for the input guys. It just kind of troubles me that I am getting the mileage that I am compared to new, which was much higher. Yeah, the sand paper sound i think may be my back brakes. The problem is you can't hear it with the windows down, only up. (I hope its not the transmission) Also, it looks like the only fuel filter is at the pump in the tank, correct? If not let me know so I can tackle it.

I have also done all the things that Saurian did. I had the dealership look over everything. I do remember that i felt a sudden loss of power while I was going down the freeway. Needed more gas to go the same speed. I was thinking a coil went out or fouled plugs, injectors, etc. Dealership said nope.

Maybe I'll change the drum brakes and have to live with the sound if that doesn't correct it.

 

[Saurian]

The fuel filter is outside the tank, roughly right behind the rear drivers side tire, as I recall... It's a large creature, about the size of a can of Campbell's Soup, which surprised me, as most in-line filters I've worked with were considerably smaller...

As far as the trans, while it is always a possibility, generally the AW4 automatic transmission is bulletproof... I've unknowingly run mine with a quart of water in it on the way home from wheeling, didn't even flinch...

 

[c12mec]

Ok. I just looked at my jeep and I went to the manufacture's manual, on my jeep the fuel filter is located at the top of the tank and tank removal is required for filter replacement. I was hoping it wasn't required. I will see what happens as time goes by. I will do whatever I need to do to keep my jeep running right. Still cheaper than new car payments.

 

[c12mec]

By the way, what do you think of the ATF+4 by valvoline? Its cheaper, just wondering if its as good. i know it has to meet specs.

 

[Saurian]

That's very odd, I've never heard of the filter being there... Doesn't make much sense that they'd change it for 1 year before discontinuing, but then again, what does make sense regarding how vehicles are constructed... Best of luck to you, here's hoping it's just one of those strange goes away on it's own things...

Don't know about that fluid, so I can offer no input whatsoever

 

[TwistedCU]

I had a 2000 XJ with the same drive train and I never got 23 mpg, even when it was all original. The best I did was around 20 mpg and that was strictly highway driving. I averaged about 17-18. Funny thing is it only dropped down to 16-17 when I put 32" tires on it, and that was accurate because I checked the mileage against a hand held GPS to get an accurate correction.

 

[c12mec]

Thanks for the help Saurian. I'll just have to keep an eye on it.

TwistedCopper-yeah, I used to get great gas mileage. By the way, I've got around 160,000 miles on my jeep. But I keep it in good shape. And, my MPG is calculated by my onboard display system. maybe its off, but I sure do feel the loss of power.

 

[c12mec]

I don't know if my last reply got posted, so here it is again...

Thanks for all your input Saurian. Nice to know that there's a place to talk about these things besides the dealership.

TwistedCopper-I get my MPG through my onboard display system. it may be inaccurate by now. Also, I do have 160,000 miles on my jeep. still looking into my sandpaper sound and "bump". Oh yeah, I had someone shift gears for me while I was looking at the driveshaft and looks like there is some slop in the drivetrain. Drive shaft moves (rotates)(seems excessive). Anyway, thanks for the insight guys. I will still monitor this thread. So reply if you like.

 

[mud4feet]

Probably not any help, but when my O2 sensors went bad on my Wrangler, I had a major loss of power and some really poopy mileage. As was mentioned before, it should trip the CEL but doesn't always........and I didn't get nearly 100,000 miles out of them. Just a thought and not a terribly expensive fix.

 

[TwistedCU]

Would a clogged catalytic converter cause a computer error code? If not then that is a possibility if everything is tuned up and you're not losing any oil due to worn piston rings.

 

[c12mec]

I had the shop remove one O2 sensor at a time and no change. Cat also checked good. No oil loss.

 

[Bounty__Hunter]

How'd they check the cat?

A clogged converter will choke the engine down, losing quite a bit of power. It gets progressively worse as the exhaust warms up and the clogged catalyst expands. Shouldn't happen on that new a jeep, but ya never know. It's covered under the emissions warranty but that is only 8yr/80k miles.

 

[c12mec]

All I know is the shop said they checked the cat and it looks fine.