TPS Voltage Causing surging ... high idle?
05-10-2007, 05:17 AM
#1
TPS Voltage Causing surging ... high idle? Just a guess it might be a bad TPS voltage ... anyone know?
Changes recently made when this started:
Added FAST 90/90 plus SLP 85MM MAF
Symptoms:
On cold start it idles at 1200 rpm for 2 minutes ... then idles down and surges when I put it in gear ... 5-6 times until it dies. Driving at any speed after a few minutes, it idles at a constant 1200 rpm. Turn on the AC after the motor is at normal operating temp and the idle goes up and stays constant. Tapping the accelerator USED TO make it drop back down to 800 rpm where it should be. Now, tapping the gass doesn't make the rpm's drop anymore. The TB isn't sticking, so, it seems electrical-related.
The dash lights pulsate (doesn't matter if it's during surging or not). Accelerating does not change the electrical pulsing. I think these are two seperate issues and I believe both issues are in the tune. The electrical pulsing was happening before the 90/90/85 seup went on (maybe a carry-over from a previous tuning session).
Anybody know what it is? It's driving me crazy.
Changes recently made when this started:
Added FAST 90/90 plus SLP 85MM MAF
Symptoms:
On cold start it idles at 1200 rpm for 2 minutes ... then idles down and surges when I put it in gear ... 5-6 times until it dies. Driving at any speed after a few minutes, it idles at a constant 1200 rpm. Turn on the AC after the motor is at normal operating temp and the idle goes up and stays constant. Tapping the accelerator USED TO make it drop back down to 800 rpm where it should be. Now, tapping the gass doesn't make the rpm's drop anymore. The TB isn't sticking, so, it seems electrical-related.
The dash lights pulsate (doesn't matter if it's during surging or not). Accelerating does not change the electrical pulsing. I think these are two seperate issues and I believe both issues are in the tune. The electrical pulsing was happening before the 90/90/85 seup went on (maybe a carry-over from a previous tuning session).
Anybody know what it is? It's driving me crazy.
05-10-2007, 10:35 AM
#2
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I'd check the vacuum leak possibility before anything
else.
I believe the FAST TB has no air hole and you might
want to drill one that matches stocker, just so the
PCM has one less error to get over. Also see that
the blade rests on the setscrew but is not open any
more than it takes, not to bind up the blade against
the body.
If you can see TPS voltage and it's above 0.6V, you
might want to slot the TPS mounting holes in the "ears"
so that it can rotate to a proper resting voltage.
else.
I believe the FAST TB has no air hole and you might
want to drill one that matches stocker, just so the
PCM has one less error to get over. Also see that
the blade rests on the setscrew but is not open any
more than it takes, not to bind up the blade against
the body.
If you can see TPS voltage and it's above 0.6V, you
might want to slot the TPS mounting holes in the "ears"
so that it can rotate to a proper resting voltage.
05-11-2007, 05:00 AM
#3
Thanks JimmyB ... you're always very helpful. This weekend, I'll go over it thoroughly and check things over. Not really sure if I want to drill a hole in a new FAST TB ... even if the issue turns out to be a voltage or vaccum issue, would you still drill a small hole in there, anyway, if you were me?
Slotting the TPS mounting holes in the "ears" sounds advantageous, so, I'll try that this weekend and see if it helps.
Anyone happen to know an online resource where I can get graphics on where and what size exactly to drill the FAST TB hole? Or how much to slot the TPS mounting holes ... maybe 1/16"?
Slotting the TPS mounting holes in the "ears" sounds advantageous, so, I'll try that this weekend and see if it helps.
Anyone happen to know an online resource where I can get graphics on where and what size exactly to drill the FAST TB hole? Or how much to slot the TPS mounting holes ... maybe 1/16"?
05-11-2007, 10:26 AM
#5
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Working on a guy's car here with the 90/90, there was no
blade hole which is just "different" than stock. He drilled it
to stock size after we dicked with idle tuning a few times.
Seemed to help some, and the thing is, you're making it
closer to stock (the IAC-closed baseline air, anyway) when
you make -a- hole. Not the same as making the stock hole
bigger, which is taking you away from stock airflow/area in
the other direction.
But since it is kind of a one-way trip I'd leave it for after
the other possibilities.
What I think the hole does for you is, make it so even if the
PCM is retarded you don't die (as easy). And PCM has a
double digit IQ (at best) to begin with.
Been tussling with idle stability myself for a while now and
still have some issues (like, stable with A/C off but unstable
with the A/C on, etc.). I have found some improvement by
making the timing table CylAir-insensitive (MAP-insensitive)
in the idle range but I think I still have a VE taper problem
because MAP surges make AFR bounce (which if VE were
dead-on, would stay flat). And the air loop is "busy" too....
Too many gears in this gizmo. Oh, for a simple setscrew.
blade hole which is just "different" than stock. He drilled it
to stock size after we dicked with idle tuning a few times.
Seemed to help some, and the thing is, you're making it
closer to stock (the IAC-closed baseline air, anyway) when
you make -a- hole. Not the same as making the stock hole
bigger, which is taking you away from stock airflow/area in
the other direction.
But since it is kind of a one-way trip I'd leave it for after
the other possibilities.
What I think the hole does for you is, make it so even if the
PCM is retarded you don't die (as easy). And PCM has a
double digit IQ (at best) to begin with.
Been tussling with idle stability myself for a while now and
still have some issues (like, stable with A/C off but unstable
with the A/C on, etc.). I have found some improvement by
making the timing table CylAir-insensitive (MAP-insensitive)
in the idle range but I think I still have a VE taper problem
because MAP surges make AFR bounce (which if VE were
dead-on, would stay flat). And the air loop is "busy" too....
Too many gears in this gizmo. Oh, for a simple setscrew.
05-11-2007, 06:09 PM
#6
Originally Posted by Frost
Sounds like you just need to adjust your TB. What are your IAC counts like?
The former owner of the shop seems to think it's a TPS voltage reading issue. I think I'm going to just go ahead and break down and buy HP Tuners and learn to tune the thing myself. It can't be that hard with help from folks like you and Jimmyblue. I do Enterprise networking for living, anyway ... so it would be a hobby for me.
You guys think I ought to take the plunge?
