Runaway & Sticky Idle

[TheShniz]

I've got a problem, in that if I drive normally or even breathe on the throttle... that my rpm's like to stick at the high rpm, or even climb to ~4k rpm's. A quick tap on the gas peddle usually brings the rpm's back down. It's getting incredibly annoying though, and am basically tapping every time I let off the gas. To others, it just sounds like I'm revving my noisy exhaust for fun (which I'm not).

What I've replaced:
MAP Sensor, TPS Sensor, IAC Valve, PCV Valve, Throttle Body Gasket, Upstream O2 Sensor

I've also sprayed down all my vacuum lines/connections/etc and intake manifold/runners w/ carb cleaner... found a small leak @ MAP sensor, but that was it. I also cleaned the throttle body when I replaced the TPS/IAC (just normal dirt).

CEL codes:
Too rich (expected)
rpm's not within +/- 200rpms (P1294) <<< My problem
Evap leak (small)
Evap leak (gross >> every so often)
^^^^ I assume these are because I'm turbo and have a ripped diaphragm (am a 1997 btw)

Torque Android App:
Says my throttle is at ~13% at idle, and shows ~50% throttle when I'm wide open... I'm going to check the butterfly that it is indeed open all of the way, but I'm thinking I may have a wiring issue (as it has spanned 2x TPS sensors). The throttle cable itself is not sticking at all, and I've left a tiny bit of slack. Also, this car hasn't had an EGR in a decade (no hot pipe). Torque is also showing that my coolant temp is exactly where it should be, so I'm assuming I have no coolant sensor funkiness.

P.S.
I have a MP60 throttle body and get a steady -19vac at idle (at 800rpms that is)

Any ideas?
I'm getting frustrated :'(
- J

 

[weasel1G]

I would find/fix all vacuum leaks first, including evap leaks. Sounds like the TPS and/or the idle position switch is out of adjustment. Refer to this thread
http://www.dsmtuners.com/threads/how-to-adjust-the-throttle-position-sensor-tps.324431/

 

[TheShniz]

Well I found the issue: my MP60 throttle body's pulley is 'wobbly' and no longer opens and closes the butterfly in unison....

Meaning, you pull back on the throttle and it takes a 1/4" turn before butterfly moves open... you let off the throttle, and it (may) take 1/4" turn before the butterfly moves closed. And so what's been happening is the butterfly has had the 1/4" turn of play, to where it may not open completely AND (more importantly) it may not close completely. Tapping the throttle jolts the plate back in line w/ the pulley.

Was a royal pain in arse to discover, because at first blush it looks like it works absolutely perfect... until you try and shake the pulley. You can see the lock nut jiggling around left and right on side of plastic pulley. Unfortunately for me, it was probably impossible to tell this was happening until it got bad enough for me to see.

....SOoooooooo, I put a factory TB back on w/ a short cry as my "RAW POWER" is noticeably diminished with this factory puniness. BUT my sob quickly ended when I spun it around the block to find my suffering was finally over.

As I couldn't get a socket around the lock nut due to the itty bitty clearance in the side of the pulley... I called Modern Performance, and asked them if it would easily pull apart to see what all is happening. They also said that I could send it in to them as they should have some spare parts lying around to get it back into shape (which may very well be the thing to do if the pulley/etc is too far gone).

My S20G-H is begging for more air, but it hasn't driven this good in quite a while!!!

P.S.
Even fixed, Torque on Android is reporting TPS of ~10% @ idle and ~50% at WOT... so I'm not sure if I can trust the reading without checking a voltmeter.

- J

 

[weasel1G]

Good to hear you got it figured out.