kick runs great, then barely runs, acts like cylinder or two not firing, then runs fine.  comes and goes.  one little box behind battery on wall had wire broken off at circuit board. .  box is one inch by two inchs.  says super intelligent sensor.  tried to reattach broken sensor wire, not sure if good contact.  Anyone knows what this box is.  kick had above symtoms even with broken wire, so I don't think it is primary problem.  Trying to fix two months now.  Anyone have any ideas?  Need to read ecm codes next.

Have you got a pic of that box? Does it look like it might be an aftermarket device? I think you need to pull the codes, do you have a Check Engine Light showing?  Make sure that you pull the codes with the engine running as some of the codes aren't stored. ie don't turn off the ignition after the fault has occued.

Check Engine light is on today, runs bad, don't think its fuel related do to eliminations.  I will read the codes with vehicle running.  Book list codes and says to jump two terminals on what looks like a plug in or a four terminal port?

replaced little box with one from yard.  Still having big problems.  Have not been able to read codes?  kick blows blue smoke when check engine light is on and I can smell gas.   when light goes off and engine runs fine no smoke.  can't  see any fuel leaking.  Think it is not firing on one or more cylinders but tuneup has been done.  Going to have ecm rebuilt as Dealer says $1500.00 to replace.  Does anyone know if you just plug in and go or do you have to talk to ecm to time, etc ? 

It sounds very much like a duff ECU. Replacement should be plug in and go.

 Have not been able to read codes? 

Is it because you need to know how to do this, or is it not giving codes?  You could take it to the Emission Test Facility (if you have one) and they will run the test and tell you the codes. (At least they do here in Arizona).  Other wise you need to look for procedurs here or in your manuals if you have one.  I'm not trying to sound harsh, I just don't have the time to research this right now.

kick blows blue smoke when check engine light is on.

Blue smoke is from oil burning. Could be valve stem seal problems, worn piston rings, and may need of an engine overhaul. 

How Many Miles are on it?

I can smell gas.

You really need to track down the source.
Is it from the engine bay or underneath?  If underneath, check your fuel lines.  If in the engine bay, check the fuel system. 

Fuel evaporates quickly, so if your lucky (or unlucky) the leak will be large enough for you to visually see.  I would pay extra attention to the Fuel InJector O-rings. (If you have Fuel injectors)     

when light goes off and engine runs fine no smoke.   

I was under the impression once it detects a code, it keeps it until cleared?

I'm kinda of new to Geos, so I'm sill learing what years have what type of Diagnostic Tests and Fuel systems, so please take me advice with a grain of salt.

Before you do anything with the ECU, you really need to take the time and check the Codes and find the source of the fuel smell.

Thanks for all the responses.  Had to cancel Moab trip due to vehicle down.  1)  have manual that says how to read codes but procedure is not working.  2) smoke and fuel smell only happens when vehicle check engine light comes on, then light will go off and engine runs good, no smoke, no fuel smell.  like night and day vehicle runs good then bad.  3)  can do leak down and compression test but I don't think engine bad because problem comes and goes.  think smoke is unburned fuel.  MAIN THING is not being able to read codes.  book says to jump two terminals and only shows drawing.  this is an obd 1 system.  one possible  is that engine has been replaced with newer year and is an obd 2 system.

If codes are not working I would do this first since it is a cheap and easy fix.

Clean EGR Valve.
The only thing it will cost you is some carb cleaner, a busted knuckle, and a little frustration getting the bolts back in.  (Clean the tube that goes from the EGR to the upper Intake Plenum too.)  Seems like a lot of intermit problems happen when you have a sticky EGR Valve that will not open or close when it's suppose to.

When egr valve is removed, clean it real good.  If you have no vacuum kit, just suck on it and verify the valve is opening and closing.  (I'm can not be held responsible for your lips falling off  , i still have mine  )


If it still runs rough, then try resetting the codes and re check them.
Take off the drivers side speaker and move the Code Reset Switch to the other position (2 positions).  I did this on my brother-in-laws 93 Tracker, and it fixed his check engine light.  This switch was mounted on the upper Passenger side corner of the Drivers Side speaker dash hole on some sort of pillar, you can't miss it.

His check engine light would always stay on and never go off.  I set the switch to the other side, and it when out.  (His tracker always ran like a champ, just always had the check engine light on.)

I do believe your Engine Code Plug (where you jump the to wires) is located in front of your battery.

Maybe it could be your Fuel Pressure Regulator?  If it runs rough and smells like gas when your first start it, it could be leaking fuel which will pool up.  It will run rough and smell at first start up until all the fuel is burnt then will run fine.  If it's really messed up it may cause fuel pressure problems during operation too. 

You might find a fuel pressure regulator in a junk yard and slip it in your pocker  , but it would be easier if you know somebody with a Tracker and tempory install theirs on yours.

Good luck

If you can't get any codes then more than likely the ECU is dead/dying, you should at least get 12 (Normal), there are a few codes that aren't permanently stored but no Code 12 is a bad sign. It sounds very much like the usual end of life capacitor failure. The injector is probably being held ON  hence the smoke and poor running. The CEL will come on by default when the processor fails, when it recovers then the CEL will go out. No codes will be stored because the processor wasn't running.

Sounds like you really need somebody with a tracker so you can not only borrow the fuel pressure regulator but a ECM to. 

That would be a perfect world, wouldn't! 

Here is some info I found on the web for checking for a clogged cat.

To test for a plugged converter, drill a small hole in the exhaust pipe right before the catalytic converter. Install a temporary hose fitting and attach a long rubber hose and a 0 to 10 pound pressure gauge. With the gauge inside the car, drive up a hill or accelerate and read the pressure. Normal is 2 to 3 pounds, restricted 4 pounds or higher. The drawback to this method is the small hole will need to be welded shut after the test; a minor job if you have a welder.

Hope this helps!

Thanks to everyone for all the response.  Armed with this info I am attacking the problem on all fronts.  ECM is being rebuilt just to eliminate, but am going to clean egr valve and break the code situation.  Kick still looks good sitting out front; is much more fun when it runs. 

Did finally get the computer out and am having it rebuilt, but I don't think it is the problem.  Think it is going to be a plugged cat or a sensor.  There is a box that that sits above the brake pedal under the dash that looks like the computer .  Took it out by mistake, it is a circuit board with a chip and diodes on it and has one wire harness going to it.  Does anyone know what this box is?

On the road agian.  Problem was bad fuel injector and some wireing problems in the injector harness.  Fuel smell and smoke was unburnt fuel.  Zuks running good so far.  I would still like to know what the box was I pulled above the brake pedal thinking it was the computer.  Got a lot of advice from vendors on ebay about locating the right box.

I swapped that out before and had some odd issues also....

I.E my engine stalled...then was fine....then rich....it finally worked out ok though...

didin't fix my check engine problem...

I don't this will help any but just something I had happen to me

On the road agian.  Problem was bad fuel injector and some wireing problems in the injector harness.  Fuel smell and smoke was unburnt fuel.  Zuks running good so far.  I would still like to know what the box was I pulled above the brake pedal thinking it was the computer.  Got a lot of advice from vendors on ebay about locating the right box.

     Is your brake light on?  Maybe the box was the electronic brake control?  Just a guess.