94 tracker stuttering

[dstaheli]

I have an 87 samurai with a 94 tracker 16v MPFI engine. It has an issue where it will hesitate or stutter while cruising (not accelerating or decelerating).It is pretty consistent. I can't drive for 10 min. without it happening. It's more noticeable after it's warmed up. I have also noticed that the idle speed will sometimes drop from 800 to about 500 periodically when it is warmed up or vary between 800 and 500. not sure if there's any connection between the 2.

I have seen DTC 21 one time and 51 a couple times. but does not regularly occur(I have been driving for weeks with no codes.)

If I unplug the TPS the hesitation/stuttering completely goes away. The idle still drops/varies the same.

If I unplug O2 sensor it doesn't seem to make a difference

If I unplug the MAF sensor the idle goes up a bit (around 800 - 1000) hesitation/stuttering is the same.

I replaced the TPS with a new TPS and it runs the same.

Any ideas?

[fixkick]

welcome, I will comment in line....
I have an 87 samurai with a 94 tracker 16v MPFI engine.
It has an issue where it will hesitate or stutter while cruising (not accelerating or decelerating).
Tuneup time,spark plugs wires ,cap , rotor?

It is pretty consistent.
I can't drive for 10 min. without it happening.
It's more noticeable after it's warmed up.
I have also noticed that the idle speed will sometimes drop from 800 to about 500 periodically when it is warmed up or vary between 800 and 500.
top cause of 500 rpm is EGR valve sticking open.

not sure if there's any connection between the 2.

I have seen DTC 21 one time
and 51 a couple times. but does not regularly occur(I have been driving for weeks with no codes.) 51 is EGR failure.
TPS Throttle Position Sensor Circuit too high V , TP pin, not idle pin, bad TPS or ground pin, wire loose or broken.

cruising and it stutters, is misfire. and not TPS cause, the MAF runs fuel cruising for sure if 02 unplugged.
stutter misfiring cruising is spark related, but if spark tips are black or old plugs the plugs are bad or fueling is way rich all the time and is other causes.

If I unplug the TPS the hesitation/stuttering completely goes away. that is because it goes to limphome mode, with very rich fueling.

The idle still drops/varies the same.

If I unplug O2 sensor it doesn't seem to make a difference (good test!)

If I unplug the MAF sensor the idle goes up a bit (around 800 - 1000) hesitation/stuttering is the same. (same thing this is LIMPHOME and super rich no MAF.

I replaced the TPS with a new TPS and it runs the same. (calibrate it first? if not calibrated the tip in throttle hesitates.
if calibrated wrong 2 ways, here is the results.
1: idle switch open all time, TPS no idle controls at all
2: idle switch opens late, hesitation.

Any ideas?

first make sure spark parts are fresh.
then make sure the spark plugs do not burn carbon black on the tips, gap is 0.028" for sure never wider.
the tps calibration is with feeler gauges and a voltmeter key on or ohm meter unplugged. The idle switch pin is the correct pin to measure.
good luck

[dstaheli]

I installed the new TPS and calibrated it according to the instructions I found on this site. I'm pretty confident it is calibrated correctly. I have replaced the spark plugs and gapped them to .028. I have not done wires,cap, rotor.

I have driven it for a couple days with the new TPS and I am getting a fault 22 again (I believe this is the same TPS related fault I mentioned above. I said 21 but i think it acutally was 22). Having already replaced the TPS with a new part, what else should I be looking for on this fault 22? I am hoping this is causing the hesitation/stuttering because with the TPS unplugged I never have the issue.

[fixkick]

94 16valve.
22 DTC means:
TPS Throttle Position Sensor Circuit too low V , TP pin, not idle pin,
ok that is way more SERIOUS THAT, code 22, stuck low is, THAT, totally different symptoms.
that means the 5vdc pin is dead, or the TP pin is shorted to ground at harness.
the TPS has 4 pins.
Ground pin 1
+5vdc reference (power wire from ECU) pin 4 (think of this as 5v battery pin, it is a 5vdc VRM voltage reg module inside the ECU and can go bad)
TP pin 3 (aka, modern name throttle angle pin. at keyon or idle is about 1vdc here.
and the idle switch pin, 0v idle 5vdc not idle. pin2

so if the ground wire breaks, the code 21 happens (TP stuck high) but this is not it.
if the 5vdc pin is dead, the TPS is dead. all the time, for code 22.
make sure the wire there are not damaged. or TPS pins not corroded. or looking green from copper oxide damage.
use your voltmeter, and land on these pins. see these ....? pin 4 is 5vdcm pin 3 is 1vdc. meter black negative test lead on BATTERY minus lug is best. (key on or idling)@!
probe with meter lead red.
click image there 1 time to zoom it and again to unzoom it.
http://www.fixkick.com/ECU/92-95MPI-eng-...e-huge.png