Faulty TPS or something else?

I appreciate if someone could help me to diagnose the following symptom
on my 89 Toyota Pickup, V6, 5spd, 4X4.

When gas pedal is slightly pressed, the check engine light will flash
once quickly, and the engine will hesitate/stall when the flashing
happens. After accelerator passes that slightly pressed position, the
engine responses normally. Checked idle speed and timing, both are
fine. Tried to read out error code from computer, if the accelerator
fully relaxed, the check engine light flashes steadily, which means no
error codes; if the accelerator if pressed, there is a 51 code, which
indicates a faulty throttle position sensor. Checked and adjusted TPS
several times (in specifications after adjustment), the symptom remains
the same. In the end, I pulled off the connector of TPS, the symptom is
still there, not better, not worse, can't tell any difference.

I have the following questions,
1. Should I press accelerator when reading error code? In other words,
is the 51 read out while pressing accelerator valid?
2. What would be the effect of running engine with TPS unconnected?[color=blue]
>From my experiment above, can you tell if the TPS is good or bad? I am[/color]
leaning to replace TPS, but would like to have evidence showing the TPS
is dead.
3. To me, the problem seems to be related to throttle position or RPM.
If is not due to TPS, what else could go wrong, and how do I test?

Desperately looking for a clue. Thank you.

On 19 Jun 2006 11:30:05 -0700, [email]mixedsig@gmail.com[/email] wrote:
[color=blue]
>I appreciate if someone could help me to diagnose the following symptom
>on my 89 Toyota Pickup, V6, 5spd, 4X4.
>
>When gas pedal is slightly pressed, the check engine light will flash
>once quickly, and the engine will hesitate/stall when the flashing
>happens. After accelerator passes that slightly pressed position, the
>engine responses normally. Checked idle speed and timing, both are
>fine. Tried to read out error code from computer, if the accelerator
>fully relaxed, the check engine light flashes steadily, which means no
>error codes; if the accelerator if pressed, there is a 51 code, which
>indicates a faulty throttle position sensor. Checked and adjusted TPS
>several times (in specifications after adjustment), the symptom remains
>the same. In the end, I pulled off the connector of TPS, the symptom is
>still there, not better, not worse, can't tell any difference.
>
>I have the following questions,
>1. Should I press accelerator when reading error code? In other words,
>is the 51 read out while pressing accelerator valid?
>2. What would be the effect of running engine with TPS unconnected?[color=green]
>>From my experiment above, can you tell if the TPS is good or bad? I am[/color]
>leaning to replace TPS, but would like to have evidence showing the TPS
>is dead.
>3. To me, the problem seems to be related to throttle position or RPM.
>If is not due to TPS, what else could go wrong, and how do I test?
>
>Desperately looking for a clue. Thank you.[/color]


It would not hurt to change it as it could be it. Next thing to check
would be MAP sensor or MAF sensor.(if present on that model)
-----------------
The SnoMan
[url]www.thesnoman.com[/url]

MAF checked to be within specs. Not sure if it is equipped with a MAP.

Tested the hesitation/stall with a Tacho meter. Stall happens around
1500rpm. RPM drops 200 from 1500 momentarily, then ramps across 1500
steadily.

On 19 Jun 2006 18:33:48 -0700, [email]mixedsig@gmail.com[/email] wrote:
[color=blue]
>MAF checked to be within specs. Not sure if it is equipped with a MAP.
>
>Tested the hesitation/stall with a Tacho meter. Stall happens around
>1500rpm. RPM drops 200 from 1500 momentarily, then ramps across 1500
>steadily.[/color]


It has a MAP, it may not be called a "MAP" but it has one rest
assured. Some older Toyota models did not have MAF's but they had
MAP's. You might put a timing light on engien and watch what it does
when it does this. I have a 2000 chevy truck that acted a bit strange
at times and it turned out it was cause by erratic timing (it never
coded) from a flakey position sensor. I found it by monitoring the
timing.
-----------------
The SnoMan
[url]www.thesnoman.com[/url]