Offcamber1

I've been having problems with my 94 22re 4x4. Starts fine, settles into a smooth idle, warms up and idles down, then a few miles down the road it stumbles and sometimes dies completely. Eventually fires up again and then you can drive it no problem until the next time you turn it off. Let it cool down then the same thing the next time.

In the last 5 months I have replaced plugs, wires, distributor pickup and coil (had a missfire I was chasing.) In the last month I've replaced fuel pump, internal screen, and fuel filter up at the motor. When I replaced the pump (through an access hole in the bed floor) the inside of the tank appeard clean. No sediment on the old pump screen either.

How do you tell if the problem is bad fuel and what the heck do you do to get rid of it if it is indeed the problem?

Thanks,

Kip

jennygirl

Check the coolant temp sensor- the one for the engine not the gauge.

When it goes bad it reads cold all the time, which can cause a car to run rich once it warms up.

Pull the plugs the next time it dies.. see if they smell like gas? And use a multimeter to check the resistance at the sensor when it is hot and cold. I believe it is a green plug near the front of the thermostat housing next to the cold start timing switch.

If the sensor reaistance checks out okay, check the voltage at the ECU pin THW. It should drop as the car warms up.

You will find this

JasonYota

iTrader: (1)

Is it throwing any codes?
An engine running rich won't stubble and die, one running very lean will cause multiple misfires and eventually stopping the engine.
Buying gas from a different fuel station would be the first thing to do.

scope103

It doesn't sound like water, but that's easy to elimate with a product like "HEET." http://www.goldeagle.com/brands/heet (It's 99% methanol, which is miscible in water, so it "dissolves" the water into the methanol, which carries it into the fuel, and it all gets burned up.)

Another very easy test is to check the timing; you'll need a $20 timing light, which you should have already.

RJR

You can check what the O2 sensor and the ECU think about the mixture pretty easily with a multimeter and a length of doorbell wire. Run the wires from the E1 and the VF1 pins of the diag connector back through the firewall and into the cabin, and connect them to the multimeter. (the E1 connection goes to multimeter LO)

Drive around to get the engine warmed up and then find a level section of road and drive at a moderate constant speed. The following table interprets the voltage readings.
* 2.5 volts -- mixture is correct
* < 2.5 volts -- mixture is rich and ECU is compensating
* Stuck at 0 volts -- mixture is rich and ECU has run out of range to compensate
* > 2.5 volts -- mixture is lean and ECU is compensating.
* Stuck at 5 volts -- mixture is lean and ECU has run out of range to compensate.

If you do this same test with TE1 grounded to E1, you'll see a conditioned version of the O2 sensor output. It should be switching about once/second between 0 and 5 volts. If it's stuck one way or the other, you either have a bad O2 sensor or the mixture is out of the control range of the ECU. Stuck at +5V means it's running rich, stuck at 0V means it's lean.

Either do this on a lonely road or have a helper to drive while you look at the meter. Stay safe out there:-)