Hello, lots of interesting stuff here, thanks for the forum! I searched from top to bottom without finding a similar issue, so I hope someone can help me. This is my work vehicle and I need to be able to drive it tomorrow if at all possible!

The truck is '95 Tracker 16V MPFI. 3 days ago I almost ran out of fuel (the gauge was so far on "E" that I was sweating bullets) but I got it filled at a never-before used vendor (Shell) and drove home without incident. The very next day, the car would not run right. It was very difficult to start but once started, idled okay and ran reasonably well while cold. As soon as it warmed up however, it began stumbling badly, almost as if it was running on three or even two cylinders. About 1/16th of the accelerator range is usable, anything over that causes continuous misfiring and stumbling. I assumed this was a slightly clogged fuel injector or perhaps some poor gas, so I added some FI cleaner to no avail. Later I added some gas drier, and that also hasn't done anything.

Here's what I know and have already tried:

1. '95 Tracker, 51k miles, original sensors and emissions equipment. "Check Engine" light came on at 50,000 miles and I've not bothered to reset it yet. Disconnecting the battery terminals for two minutes did not reset it.

2. Compression = 150 PSI+ for each cylinder, even though one or two valves sometimes tap loudly and should be adjusted.

3. Plugs were carbon-sooted when investigated. Cleaned, quickly became sooted again (read: very rich fuel mixture.) Replaced plugs and rotor, cleaned distributor, no change. Wires on order. Gas mileage has never been especially great in this vehicle.

4. Fuel filter had never been replaced so I replaced that, no change (big mess though!) I even popped the nut on the fuel rail and cycled the ignition a few dozen times to "purge" any contaminants I might have introduced, no change. I did notice that fuel continued to "seep" out of the fuel rail after the pump had shut off... is it supposed to do this?

5. Timing light was broken, could not test for timing issues...

6. EGR valve does move slightly when cold with finger pressure, perhaps 1/16th or 1/8th of an inch - this seems to be its entire limit of travel, is this normal?

7. Air filter is perfectly clean. Oil and filter was just changed.

8. Cannot get computer to give me any codes. I'm trying to locate the ECU switch now. It would not reset after two minutes of disconnected battery, however.

9. Unsure if operating in "open loop mode."


Any ideas? Please help.

Regards,
Mark

Flipped the switch near left front speaker, Check Engine light went out, still stumbles badly. Disconnecting battery for an hour or so. Manually moving the EGR valve caused engine to idle rough as expected. Still cannot get any diagnostic codes - here are some photos, click for larger versions.



Is this the right connector, pins 2 and 3 should be connected, correct? This differs with what my Hyner manual shows.




Are one of these also the OBD1 connector? And if so, which pins are 2 and 3?

Thanks a lot.

my 90 samurai did the same thing.  it happened while i was driving it.  the coil went out.  it has an electronic coil pack not the standard round style.  i had to have a diagnostic check done just to figure it out i tried everything else.

Top photo - I believe the other connector you're holding is the diagnostics connector.



Bottom photo, I'm pretty sure its the black connector. Blk/White is 12V, green is earth/ground and the other (maybe violet) is the diagnostic output. That connector may not be any use to you as it is a single wire interface (OBD2 or ALDL maybe). You'll need a scanner
Someone posted a link to service manuals the other day. If you download the one for your vehicle then you can verify this from the wire colours.

Excellent Rhinoman! My lousy Hyner manual showed the 4-conductor cable as being the diag port, but said the rubber-covered plug was the diag port (and didn't give a pin-out.)

I will try this and look for the link to the service manual, and test the coil - thanks!

I researched http://search.epnet.com/login.aspx?authtype=url,uid (from an earlier thread) and have begun some tests. First, I managed to get the diagnostic readout working, yay! Just jumper pins B and D using the above illustration. Unfortunately it only read out 12's, since I reset the thing yesterday.

The O2 sensor doesn't seem to be within spec. At 1200 rpm with engine warm, its output is supposed to vary between 0.1v to 0.9v but it stays over 0.5v. Are higher readings indicative of rich mixture? Because the vehicle runs exactly the same WITH or WITHOUT the O2 sensor connected - not sure exactly what that means if anything, but I assume it would run worse without it and there is -zero- change. Can anyone confirm or deny this? It will be replaced tomorrow.

Well I replaced the plugs, wires, distributor cap, rotor, and O2 sensor and it appears to be running well. The O2 sensor might have been okay but it did have 50,000 miles on it and the OEM replacement schedule is 60,000. I think the problem was the plug boots - and these were the expensive Bosch set! Do yourself a favor and don't bother, get the mid-priced variety. And don't goop silicone lubricant into them like I did - use a toothpick-full per boot, max. I tried to remove the boots with the engine warm and two of the rubber ends got stuck on the plugs, in the plug well! That is a serious pain in the ass to fix, don't do it...

Got the truck stuck in an alley for a few minutes while testing it out, whoops! Low gear is awesome in these trucks though, a little rocking and she was free. Should have known better than try tackling a four-foot-high snowdrift, even bent my license plate pretty good.

even bent my license plate pretty good.

I'd count that as TRAIL DAMAGE!!! 

There has been alot of problems with aluminum dust in the gas tank cloging up the screen to the fuel pump, it is from the gas nozzle's they are made from a real soft aluminum and when you pull it out of the tank it shaves a little off each time. ( drop tank clean repeat.)

The O2 sensor doesn't seem to be within spec. At 1200 rpm with engine warm, its output is supposed to vary between 0.1v to 0.9v but it stays over 0.5v. Are higher readings indicative of rich mixture? Because the vehicle runs exactly the same WITH or WITHOUT the O2 sensor connected - not sure exactly what that means if anything, but I assume it would run worse without it and there is -zero- change. Can anyone confirm or deny this? It will be replaced tomorrow.

Over 0.5V indicates lean running but you probably didn't have the engine/exhaust hot enough to get a reliable reading. The sensors aren't accurate enough to give an exact reading of the mixture. The readings are also quite temperature dependant so the ECU doesn't use the sensor under low loads or high loads. The voltage only varies when the ECU is in closed loop mode, the ECU drives the mixture lean and the rich alternately trying to keep the mixture around the 0.5V mark. If the sensor is faulty then the ECU will run its default settings (Open Loop) all the time.
If the sensor hasn't been changed for some time (recommended = 30K) then its worth changing because they get sluggish with age

I had an Isuzu Stylus that always ran great when I lived in St Paul, MN. Then one day on the way to work I stopped and filled up at a gas station I never had used before. That car ran like crap for 2 tank fulls of gas. Maybe that will be it, I don't know.