Tuned up '93 6 cyl runs great - still have poor mileage

[JWood]

I started out trying to rid the engine of acceleration clatter/ping on 87 octane (170k miles). New plugs, wires, fuel filter, PCV valve, Slick 50 Injector cleaner, throttle body cleaner, ran Seafoam in the tank on 10 gallons, new air filter, cleaned MAS, and an oil change. Runs great, much better and the clatter is about 99% gone, but mileage is poor:

City = 13 MPG and Highway 16 MPG.

Seems to me years ago I got about 16 City and 21 Highway. Do you have any thoughts on what else I could do...what did I overlook?

 

[JGAMBLE]

at 170k it seems to me that you're gonna have some blow by around the piston rings. If that's occuring you're losing compression. The motor's probably having to work harder. just my .02

 

[jimbo74]

actually, that mileage sounds about right...... most engines seem to go downhill over time, no matter what you do to them... have you also replaced your 02 sensors? that mileage for a first gen actually seems to be quite good......

 

[Rhett]

Quest for 30!!! ahahaha

I think your mileage is typical for 1st gen.

I have 1st gen and all I get is 13 (town) and 16 (highway). Yours sounds about right, even though you have a 2WD which is lighter; but yours is an XLT (4 door) and mine is a 2 door so the weight difference is probably negligible. I have 3.27 gears, and some pretty standard mods, and my tires are 3/8" larger than P235/75's (not much difference but a little).

Anyway mine has 99000 miles and runs great, I've done all the maintenance (O2s as well). 13 in town and 16 highway is the best I get. Sometimes it's more like 12/15 if I hot rod it too much. Factory spec calls for 16/20. Sure..... (wouldn't that be nice)

oh and I also have a vent visor which I'm sure hurts mpg a bit on the highway...

 

[410Fortune]

dont forget about tire pressure, lubing the chassis, wheel bearings, changing the fluids in the t case, tranny, and rear axle..............

All these things help mileage and then some

Check out Aldive's truck he is constantly trying for better MPG and its working, mods that save you $$$ at the pump pay for themselves........now if I could just get cash back for 4x4ing!!!

 

[Rhett]

My truck burns more gas at IDLE than Aldive's truck does at full throttle

 

[JWood]

I read that post about 30 MPG.

Sounds pretty incredible; I'll never see anything close to that. With 170k miles, I guess I'll just continue with regular mantainance & maybe look at changing the O2 sensors sometime.

At least I got rid of the clatter, it was driving me crazy.

Thanks for the input guys.

 

[simmons1]

If you have a 93 and have not retorqued both the upper and lower intake manifold bolts then that is definitely 80% of you problem. My mother's 93 has 180K+ and pinged like crazy. I retorqued the bolt, which were extremely loose and with a tank full of 93 and a bottle of Techron the ping dissappered. My mother runs the cheapest gas, so it has started to ping a little lately but not near as bad. Th mileage also increase. Some of the bolts are hard to get to but with a set of extensions and a univeral on a ratchet you can do it in under and hour.

 

[JWood]

Thank Simmons...

Ive tightened the upper bolts but haven't located the lower ones...they must be tough to get to.

 

[Iggy flywheel]

You might want to check the MAF. If the volts are out of specs it can cause bad gas milage. I would replace with the Pro meter can find threads on them.

 

[simmons1]

The uppers are nut on studs and the lowers are actual bolts going into the engine block and yes they are extremely hard to get to. With a set of extensions and a couple of swivels on a rachet I can get to all of them "fairly" easy. With out the extensions and swivels it is not possible. You should definately try to tighten them. How much did you get on the uppers? half turn or so? I would say about half of mine were a 1/4 to 1/2 turn loose.

 

[simmons1]

BTW, the lowers are on the manifold that the studs for the upper are attached too.

 

[JWood]

Thanks for advice on the intake.

I did try to tighten the uppers but they would move only slightly. So, I 'll try to get to the lower ones and see what happens with them.

 

[njsjfonline]

upper and lower

intake bolts.
I just removed the upper intake to get @ the lower.
It looks harder then is really is I had taken about an
1 2/1 hours to do it.
After that all the chatter was gone.

 

[MrShorty]

I also typically get about the same on my '92 (160k miles). The thing that has me scratching my head, on a recent trip, I got ~19 mpg over 150 miles. But the next 100 it was back down to 17. I started a thread about it, and it was suggested that maybe it was something in the gas, or just plain luck, or other causes. If you figure out how to get yours up, let us know. Perhaps the worst part of my experience is that, it appears to be capable of getting ~20 mpg, if only I could figure out what happened to get it there.