Best gas mileage possible

[tweakedlogic]

Heated O2 sensors have a life expectancy of 80K. Unheated, less. I think the newer wide bands have a longer life.
When I bought my Ex it had 175k on the clock. It got about 12 MPH, and ran like **** even after tune up, but had no codes. I replaced the 02 sensor and it immediately ran great. It seems that they can loose accuracy with age. Not enough to throw a CEL, but enough to kill fuel economy and run poorly. $30 every 3-4 years is worth it to me.

 

[Naasau]

Heated O2 sensors have a life expectancy of 80K. Unheated, less. I think the newer wide bands have a longer life.
When I bought my Ex it had 175k on the clock. It got about 12 MPH, and ran like **** even after tune up, but had no codes. I replaced the 02 sensor and it immediately ran great. It seems that they can loose accuracy with age. Not enough to throw a CEL, but enough to kill fuel economy and run poorly. $30 every 3-4 years is worth it to me.

x2!!! I had the same issue with the Beast, numbers weren't as drastic, but the idea holds.

 

[bovine]

With all the replies it seems as if i'm getting as good as can be got with the 94 since it does not have the obd 2 port to do custom tunes to it so i'll just leave it alone until it starts getting worse mileage so i don't screw up a good thing.

 

[Anime]

You should still do the regular maintenance items. Cleaning the MAF, replacing fluids with synthetic, maybe even throwing on new spark plug wires if the ones on it are stock, etc. Even a replacement air filter can add some power/torque even if it doesn't change the mileage numbers a whole lot.

 

[masospaghetti]

The cat-back system (at least the Dynomax) actually will improve mileage if everything else stays the same, since it makes the system more efficient. Usually a better flowing intake, whether it's a better-flowing replacement filter or a cold-air conical filter, helps mileage as well.

I have to disagree with you on this. High flow intakes and exhaust help max power because they increase max flow - but at lower power settings, such as cruise (where fuel efficiency is important), having a big intake and big exhaust actually slows down the incoming air charge, and exhaust stream, making it slightly less efficient.

Also, cold intake air helps power, but not efficiency. It helps power because cold air is dense and can combine with more air molecules at the correct 14.7:1 burn ratio. However, cold air also takes energy to heat up which is robbed from the combustion. You'll see on some forums with smaller cars people actually install *warm* air intakes on purpose, because the hot intake charge is better for efficiency.

 

[Anime]

Well you can disagree, but the 93-94's have pretty restrictive exhausts (just 2" from the cat back) and throwing on a Dynomax kit or even just a stock replacement 2.25 system from a 91-92 makes the entire vehicle MORE efficient because the engine no longer wastes power pushing the exhaust out through the system that's too small for it. Cruise RPM on the 4.0L is usually around 1800-2300 RPM (even higher with low gears), which is pretty close to max torque, and right where the better flowing exhaust gives a huge gain.

The KKM air intakes for the 91-94s are also not the same as a 'cold air' system because the filter is still in the stock location under the hood. They actually work more like a warm air intake around town, only when driving at speed does the air under the hood move enough to get close to the surrounding temp, but it's still pretty warm under there.

Your assumptions are generally correct, but when it comes to this specific vehicle, and these particular parts, what's available gives certain results. I've done the switch on my ride and done the math on what does what, so I'm just relaying my experiences.

 

[safn1949]

The addition of a KKM and a less restrictive muffler,along with new plugs and wires made a big difference in my 94. I run tires at 35psi and keep my vehicle maintained.

I get about 19 hwy and 16.5 city if I drive it easy.

As a side note I run stock autolite wires and NGK plugs,just a personal preference.

 

[waskly]

Heated O2 sensors have a life expectancy of 80K. Unheated, less. I think the newer wide bands have a longer life.
When I bought my Ex it had 175k on the clock.

LOL?

sorry, the pcm samples fast enough to know a good or bad sensor.

any odb2 system, less it pops a light changing them does NOTHING.

 

[Naasau]

But we're talking OBD I. And a marginal sensor is not a failed sensor.

 

[waskly]

But we're talking OBD I. And a marginal sensor is not a failed sensor.

I should look more then front page to reply to.

Yes ODB, failing sensors wont show up like in ODB II.

Didn't notice where this was posted sorry.

 

[Naasau]

It's all good. ;-)

 

[bovine]

Yea that I know of the only thing filing on my car is the a/c compressor and possibly something in the abs as I get a light that pops on randomly. I am some times a little worried about the abs light since it has to do with the brakes and I do like to stop but i can tell no difference from when it is on to when it is not I thought It may be a bad abs hydraulic control unit but that thing is expensive and I don't want to put out that kinda money. On the compressor it was slinging oil from the pulley and the clutch can I fi this easier then putting a new compressor on?

 

[Anime]

The ABS light could be anything from a dirty/damaged exciter ring (the fins on the back of the brake rotors) to a bad sensor. The sensors get old and the protective loom and sheaths fall apart, leaving the wiring exposed. It's possible for a sensor to just start going though. There's also the rear sensor in the axle that also controls the ABS.

Brakes aren't really a system to ignore if there's a problem though. If the light goes on every so often, there's a problem and you should check it out and fix it. Don't wait until you get into an accident.

If the compressor is leaking oil, it can possibly be saved by having the system evacuated, the compressor removed, and the seal replaced. If you let it continue to leak, eventually the A/C system will have no oil, the compressor will not be lubricated, and it will destroy both the compressor and contaminate every single other part of the A/C system with the metal shards that will come from the compressor pistons tearing up the unlubricated compressor. It may already be too late. Those multi-piston compressors will continue to operate until they fail in spectacular fashion.

Sounds like to already have two things to drop money on. Those should be top priority before anything else.

 

[bovine]

I'll look at the sensors first and then pull the brake rotors and check them.

Since the compressor leaked all the freon with it wont engage but I just run with the windows down anyway since it's supposed to save gas since there's less drag on the engine.