I have a '93 16V Sidekick 5spd 4 door, that's only getting about 23 mpg with non-aggressive driving. I adjusted the valves (many of them were tight), and ran some Seafoam cleaner through the plenum. It seemed to be happier, yet sometimes I could swear I have a misfiring plug wire, but then it clears up. I also have a K&N air filter on it, figuring better breathing couldn't hurt. After the valve adjustment and cleaning, I got a much higher cold idle (approx. 2500rpm). What's going on? Could this be an ECM that's demonically possessed? Most of the time it runs fine; just crummy mileage, and the intermittent power loss. I was thinking about putting a Thorley header on (they state that it's 50 state legal). A Calmini header is a bit cheaper, but they say it's not 50 state legal, and it appears to be shorter on length, requiring a collector. Any input, or advice, or experience? I'm not going off roading; this is my commuter car, and I need the 4wd for snow, and I want it to be an economical ride. 

23 isn't too bad, that's the best I ever
got in my 89 2 door 1.6 8V engine, even
new.

I have a few ideas about fuel milage, and
how to improve it.

1. Use 5w-30 engine oil
I am going to try and see if a lighter weight
oil in the T-case will help, You might know I
have been working on a Slip Yoke Eliminator,
and in the process of tearing down the T-case
I learned something, the gears in the T-case,
even the low range ones are always turning,
even in 2WD.

Well this is a major drag on the engine, and a
lighter weight oil would help reduce drag, and
in cold weather, gear oil is like grease, lots of
drag, even when warm, 90Wt gear oil is heavy.

I have been thinking about a blend of 50/50 ATF
and the lightest gear oil I can get, probably synthetic
stuff, and check the mileage. many new 4WD systems
are using ATF Straight, and I used ATF  in a motorcycle
trans and never had a problem, also, automatic transmissions
have gears inside, planetary sets and such, straight ATF would
probably work just fine.

I might lighten up the diff oil too and see if it helps.

Thoughts from the forum ?

Wild

Check your tires. Inflate to spec, or a bit higher if you are willing to sacrifice ride and handling.
 

How old are your plugs/wires? What you are saying is just what the ing. system does when it.s breaking down. If your wires/plugs are old replace them with good/new ones. I have a 96 X90 but I run Nology wires & ND plugs. As you know newer veh.s get better mpg & they have hotter ing. systems. Nology wires jumped my X90 (1600) up 2mph over good stock plug wires. Eather way plug wires/plug are a good poss. cause.

23 is about what I get on my '96 16V with the tires inflated to the "Factory recommendations" (23psi).  Increasing the pressure to about 32 brings it up to about 28 or 29 MPG in warm weather and about 26 in cold weather.

Rides like a brick, but worth it to me...

I have found what I think is a solution for
a light oil for the T-case, and for you Man.
trans guys, it should work well too.

It's Red Line Manual Trans Fluid  MTL in the
Red Line book, it has a GL-4 Classification and
is thinner than ATF in extreem cold conditions,
also, and more inportantly it has the right friction
index for the syncros to work right.  Not overly priced
at $9.00 a quart, regular gear oil GL-4 class will cost
$2-3 per quart, and this should help you save $$ on
better fuel economy. Average observed increase in
power transfer efficiency is 2-5%, what this equals in
MPG will need to be tested.  AutoZone is listed as a
distributor, but they don't carry the complete line 
it should be easy enough to get thru main channels
of parts suppliers I hope.

Wild

My wifes 97 4dr 16V pulls in around 27 mpg in stock trim. That's even when I drive it.  I would bet that new plug wires will help with mpg.

Royal Purple also  is offering a MTF
under the name of Syncromax available
at Pep-Boys here in Cal. GL-4 spec also
looks to be about $1 per quart less than
Red Line

I just picked up a 4 door and I am getting over 26 driving wide open all the time (I think they should change the speed limit between LA and San Diego to 90 mph) I put in new plugs and new wires from napa, also new cap and rotor. It's 94 stocker with 130K on it. Stock tires too running around 28psi.. I wonder what this thing would get if I slowed down to 65.. Then again I would be getting the horn and the finger more than normal! 

Checked Pep Boys today, they don't stock the
GL-4 trans lube  (syncromax) but can order it,
ok how much, 6 quarts min about $60 plus $65
shipping       

No Thanks, I'll go buy the bulk from Oil Can Henry's
they said they would sell bulk if I wanted, or put in
the fluid for about $50 Ohh well I'll figure something out

Trail tough sells royal purple, I put a quart in my t-case a couple of months ago, so far so good and yes you can feel the diffrence    I think around 9 bucks a quart, he should be able to get the gl-4 stuff.

1.  Air the tires up to 45 PSI
2.  Take off the side mirrors
3.  Put it in neutral on downhills

 

Tell me guise... does every 1.6 cast iron exhaust manifold crack at #4 port? I saw one at the boneyard today, cracked, like mine.

You need to fix that. It won't help your mpg at all

Rick:
Let us know what mileage you get with 32 psi.  My Sport will get 33 mpg on the highway at about 60 mph top speed with 32 psi in the tires.