95 ranger missing

[Swampdonkey87]

I have a 95 ranger with a 2.3 and it has a bad miss but you reset the computer its fine for about 15 min the goes to doin it again. What sensor can cause this problem or what do yall think thanks for the help

 

[RonD]

Have you ID the cylinder that is missing?
i.e. pulled the spark plugs

To see if it's specific to one cylinder.
If it is then swap plug wire with another cylinder to see if it changes.
A compression test would be good info to find out.

When you reset the PCM(computer) a few things happen, it will run pre-set fuel/air mix for a minute or two(timer based), if engine is already warmed up, if engine is cold it will run a little longer on the pre-sets until O2 sensors are warm enough to work, 600deg+

Once O2 sensors are on-line then PCM uses those to adjust fuel/air.

15 minutes is a long time for it to be O2 sensor issue, and would probably turn on the CEL(check engine light), which you don't mention so I assume that is not on.

A PCM reset can also cause the PCM to relearn sensor parameters, and that can take 10-50miles of driving.
MAF sensor could be the issue, besides the O2 sensor the MAF is the main sensor used to calculate fuel/air mix, easy to clean this sensor.

Could be an injector issue, on the 2.3l injectors 1 and 4 fire at the same time then 2 and 3 at the same time, this is suppose to keep the intake full of fuel/air mix all the time, so like a waste spark system only for the injectors, lol.

After engine is running in closed loop(O2 sensors on-line) the fuel/air tends to be leaner than the pre-set fuel/air(open loop).
If you had an injector that wasn't working or working well(less fuel passing) that could lean the mixture out on just that 1 cylinder

 

[Swampdonkey87]

ok we messed with it tonight and its got spark on all cyls. we also started unplugging sensors and the ce light came on then once we plugged them back in the ce light went away. then we took the valve thing out on the fuelrail to see if it had water in the fuel and no water then started it back up ran perfect. we then shut it off and when we started it back up ran great for about two min then went to missing and popping so we have came to a fuel problem we think ...any other sugestions

 

[RonD]

Water in the fuel?
There shouldn't be a time issue if that was the case.

Do you have a clip on timing light(inductance), so you can test spark while engine is missing?

2 minutes is more like an O2 sensor issue, especially if engine was already warm.
PCM has a timer that waits for O2 sensors to heat up before using them.

If O2 is reporting a false rich, then PCM will run fuel injectors leaner, which would cause missing and pops(lean mix can pre-ignite in hot cylinder, without spark)
The '95 should be OBD II so with a scanner you can watch the O2 sensor voltage, .03v is lean, .07v is rich, it will change fast, if it's steady then it's not working right.
If you unplug the O2 sensor the PCM should go into open loop, so run pre-set fuel air, if the miss doesn't come back replace O2 sensor.

There is also a possible vacuum leak issue, but on a controlled vacuum, something that is controlled by a solenoid, so it is only a vacuum leak when solenoid is open, which would fit the now it works now it doesn't problem.
A vacuum leak causes a leaner mix as well.

EVAP systems or EGR systems usually have vacuum solenoids

 

[Swampdonkey87]

Yes we used a timing light to check all the wires and there good its just so speratic cause you might start it up and run great then 5 min later go to missing then it soometimes will clear up for a few min thats why we are all lost cause if it was a sensor or vacume i would think it would do it all the time and we pulled all the plugs and they all were like brown which means running lean right. Idk gonna change fuel pump tonight and see what happens

 

[RonD]

Light brown plug would be normal, darker brown rich, clean plug would be lean.
There is no real sign of lean on a spark plug, if lean long enough plug will melt, which is a sign, lol.

If it is a lean issue and comes and goes the light brown means it's working normally most of the time, and going lean won't change the spark plugs coloring but would cause a miss.

 

[Swampdonkey87]

Oh ok we werent sure about the color but do you think the pump might not be pumping enough fuel or no think its somthing else i really appreciate you helping us with this

 

[Insanejughead]

What does your exhaust smell like?

Have you checked codes? You haven't mentioned those at all. A KOER test should REALLY help you in this case.


I wonder if your fuel pressure regulator has stopped working... Unplug the vacuum line from it and see if the miss goes away.

 

[RonD]

Fuel pump would be a long shot.
Symptom of that would be losing power at highway speeds or a no start.

A miss coming and going wouldn't cause me to look at the fuel pump.

 

[modelageek]

Fuel pump would be a long shot.
Symptom of that would be losing power at highway speeds or a no start.

A miss coming and going wouldn't cause me to look at the fuel pump.

I agree with Ron. I doubt is a fuelpump issue if it runs fine after a reset.

Besides that. never replace a FP until you do pressure tests

At this point you should be trying to catch a pending code.

 

[modelageek]

If you have a droid device you can get a scanner that reads PID's and checks for codes for $10