poor gas mileage, 2002 Trooper

[jeffryscott]

So a couple of years ago I sold my very nice 91 FJ80 because gas mileage was so poor and highway performance was, well, not so good either. I wanted a do it all family hauler, off-road, on highway truck and my previous experience with a Trooper was good so I bought another one, a 2002 model.

While this one drives great, since I bought it with 105K (now has 114K) it has gotten terrible mileage. Not much better than the 9mpg the Cruiser got ... between 9.5 and 10.5 in town and max of 13-14 on highway. My previous 99 easily got 13-15 in town and 18 or so sometimes more on the highway. Same tire size on the two vehicles.

Never have had a check engine light (and it does come on when i start the engine so I know there is a bulb).

I replaced the spark plugs with OEM after purchase and did routine maintenance (oil and filter changes) and it hasn't really budged. The tail pipe is black inside and so it seems to me like it could be running rich.

I just bought new O2 sensors, and will install soon, but Kermit suggested in another thread to check the cats.

Any other suggestions before I dig in and start getting serious about sorting this mpg thing out?

If I do replace the cats, any problems with universal fit cats vs direct fit? ($70 each for Magnaflow universal versus 300+ for direct fit, and it takes two)

Thanks,

Jeff

 

[Flagster]

I don't have a trooper but a 95 fzj80...typical 80 series mpgs (13-15hwy and 10 in town)...but very sluggish with downshifts and boggy on hills...and it stinks on startup...like gassy rotten eggs...checked my radiator for exhaust gasses and my coolant is clean but I think I may have bad cats (150K miles on original engine) and I am also thinking about replacing cats...I will be interested to see what you find and decide...

 

[Clutch]

How is the power?

Did you bench test your old O2 sensors to see if they are bad?

Have you done a compression and/or leak down test?

Is the throttle body clean?

Are the brakes dragging? Perhaps the e-brake is hanging up.

Might be a bad injector, or timing might be off.

Spark plugs gapped to spec?

Is the fuel filter fresh?

Check the fuel pressure?

Is the tranny or clutch slipping?

 

[jeffryscott]

Good list Kermit,

Have not replaced the O2 sensors yet, just purchased them (takes 4 and am told lifespan of them is about 100K) Rock Auto had OEM Denso's for $22 each.

No compression or leak down test done. Power is on par with my 99, both were running 265/75/16 tires (different brands). No oil loss between changes.

I think I cleaned the throttle body on the first go around, but honestly don't remember if I did or just wanted to. I bought MAF cleaner today and will be cleaning the MAF, Throttle Body and EGR. Changed the PCV when first purchased.

I've thought about injectors and am running BG44K through the system as we speak. Timing could be off, I haven't checked, as aside from gas mileage, it drives fantastic.

Plugs were gapped and replaced with the OEM recommended upon purchase. It has individual coil packs, not sure how to check those.

Fuel filter, haven't changed. Do have one to put in though.

Have not checked fuel pressure.

Tranny seems in good working order (flushed it about 5K ago).

How is the power?

Did you bench test your old O2 sensors to see if they are bad?

Have you done a compression and/or leak down test?

Is the throttle body clean?

Are the brakes dragging? Perhaps the e-brake is hanging up.

Might be a bad injector, or timing might be off.

Spark plugs gapped to spec?

Is the fuel filter fresh?

Check the fuel pressure?

Is the tranny or clutch slipping?

 

[Clutch]

hmmm...doesn't sound like the cat is bad, if it isn't smelling and no loss of power.

sounds frustrating.

plenty of videos on youtube on how to check the coil pack.

 

[LR Max]

hmmm...doesn't sound like the cat is bad, if it isn't smelling and no loss of power.

sounds frustrating.

plenty of videos on youtube on how to check the coil pack.

I'm going to say its not the coil pack. In my experience, they just fail and if a coil pack fails, it will throw a code (same with an injector or any kind of misfire on the engine). Same with an O2 sensor, when they ain't working, you will get a code. Same with just about any sensor.

When you pulled the spark plugs, what did they look like? No oil consumption? No intake manifold leaks? EFI pressure regulator is working?

Dunno, just throwing out some more stuff. A compression check is a capital idea as well as checking the other things mentioned. For the catalytic converter, get yourself a laser temp gauge. There will be a HUGE temp difference on the inlet and outlet of the cat if it is blocked.

 

[BIGdaddy]

would something as simple as tires or bearings or other rotational factors be something to consider?

It's really not THAT much less than normal Trooper mpgs, in my opinion.

What about things like roofracks? Did one have one and the other didn't? Farings or valances? etc?

All of those little things can add up.

I'm only going that way, because of your statement that it's really doing great as far as running condition. My trooper gets about 15 or 16 on the highway, which I know COULD be more, but I'm fine with it for right now because just like you, it's running great.

I plan on doing spark plugs, Rotella T6 oil change, manual hubs, and a tire swap in the future, so we'll have to see where I land. i'm going to try do do one at a time to see how it effects my efficiency, but anything north of 13mpgs, is an improvement over my last rig, so I'm biased..haha.

 

[Clutch]

would something as simple as tires or bearings or other rotational factors be something to consider?

It's really not THAT much less than normal Trooper mpgs, in my opinion.

What about things like roofracks? Did one have one and the other didn't? Farings or valances? etc?

All of those little things can add up.

I'm only going that way, because of your statement that it's really doing great as far as running condition. My trooper gets about 15 or 16 on the highway, which I know COULD be more, but I'm fine with it for right now because just like you, it's running great.

I plan on doing spark plugs, Rotella T6 oil change, manual hubs, and a tire swap in the future, so we'll have to see where I land. i'm going to try do do one at a time to see how it effects my efficiency, but anything north of 13mpgs, is an improvement over my last rig, so I'm biased..haha.

I think I have Jeffery worried since ours gets excellent mileage. 18 city (have seen 24 on the hwy) pulled 23.2 yesterday.

BUT it is 2WD on street tires...and I drive like an old man...take my time to get up to speed, no sudden movements, drive the speed limit (maybe a little under )

Though I believe his should get a little better than what he is getting.

 

[BIGdaddy]

I think I have Jeffery worried since ours gets excellent mileage. 18 city (have seen 24 on the hwy) pulled 23.2 yesterday.

BUT it is 2WD on street tires...and I drive like an old man...take my time to get up to speed, no sudden movements, drive the speed limit (maybe a little under )

Though I believe his should get a little better than what he is getting.

OHHHH, now i understand!!!

Instigator!

 

[madmax718]

is your torque converter locking up?

 

[Clutch]

OHHHH, now i understand!!!

Instigator!

I wasn't trying!

Was discussing the merits/cost of gas vs. diesel with Scootr29! Diesels might save you a little on fuel costs, but it ain't gonna be cheap! LOL

 

[SSF556]

OHHHH, now i understand!!!

Instigator!

I concur.....


Sent from my iPad using Tapatalk HD

 

[jeffryscott]

I think I have Jeffery worried since ours gets excellent mileage. 18 city (have seen 24 on the hwy) pulled 23.2 yesterday.

BUT it is 2WD on street tires...and I drive like an old man...take my time to get up to speed, no sudden movements, drive the speed limit (maybe a little under )

Though I believe his should get a little better than what he is getting.

Nah, it's been bugging me since I bought it. You just encouraged me to start thinking about it more seriously. I posted up on planetisuzoo two years ago when I first started seeing the bad mpg and didn't get much help, so I'm trying again, here and there. I know this rig is capable of much better mpg than I'm getting, and honestly, one of the reasons I don't get out as much as I'd like is it is too expensive.

 

[jeffryscott]

is your torque converter locking up?

I believe so, but how would you tell for sure? It cruises normally at highway speeds, think RPMs are about 2k at 65 (I was sortof watching yesterday while on the highway because I watch that crazy Kilmer guy on youtube about cleaning cats)

 

[Clutch]

Nah, it's been bugging me since I bought it. You just encouraged me to start thinking about it more seriously. I posted up on planetisuzoo two years ago when I first started seeing the bad mpg and didn't get much help, so I'm trying again, here and there. I know this rig is capable of much better mpg than I'm getting, and honestly, one of the reasons I don't get out as much as I'd like is it is too expensive.

Ok, you had me worried. (I know I tend to ramble on...)

That is a bummer, it "should" get better mpgs.

If you can't remedy the problem, are you going to sell it?