M20 idle quality issues
Ever since having a fresh head/cam put on my car by a local shop (I tpyically do all my own work) I've been fighting horrible idle issues.
I've read the archives here (and a few other sites) and people generally suggest checking out all of the switches and sensors, but in a general sort of way.
After curling up with the Bentley (always a good suggestion) it struck me (yes, I know it's obvious... but I've not seen anyone really spell it out) that the idle circuit _never even comes into play_ if the throttle position switch doesn't close.
Now after reading the Bentley, I stumbled on another issue... the local shop had moved the throttle stop screw to set up the idle... so it was likely that this adjustment disabled the idle switch.
Turns out I was right... the TPS idle switch was not closing. I redjusted the set screw per the Bentleys... and it still didn't close. So I pulled the throttle body, pulled and cleaned the switch (it was very oily), comfirmed that it was working correctly, reinstalled, adjusted it correctly... and suddenly my idle issues virtually disappeared.
The computer is still learning how to control the idle, but after just a few minutes of running it was down to a steady (if a bit low) loping idle... about what I anticipated given the cam.
So I'm writing this to make it very clear to anyone searching the archives... START with verifying the operation of this switch. You can do it without disaeesmbling anything... pull the connector and stick a mutlimeter on it to check for continuity. Three poles, the center is the common... the switch should close on one of the other poles with the throttle closed and on the other at full throttle. Before doing ANYTHING else, verify that this is adjusted correctly.
Bill
I've read the archives here (and a few other sites) and people generally suggest checking out all of the switches and sensors, but in a general sort of way.
After curling up with the Bentley (always a good suggestion) it struck me (yes, I know it's obvious... but I've not seen anyone really spell it out) that the idle circuit _never even comes into play_ if the throttle position switch doesn't close.
Now after reading the Bentley, I stumbled on another issue... the local shop had moved the throttle stop screw to set up the idle... so it was likely that this adjustment disabled the idle switch.
Turns out I was right... the TPS idle switch was not closing. I redjusted the set screw per the Bentleys... and it still didn't close. So I pulled the throttle body, pulled and cleaned the switch (it was very oily), comfirmed that it was working correctly, reinstalled, adjusted it correctly... and suddenly my idle issues virtually disappeared.
The computer is still learning how to control the idle, but after just a few minutes of running it was down to a steady (if a bit low) loping idle... about what I anticipated given the cam.
So I'm writing this to make it very clear to anyone searching the archives... START with verifying the operation of this switch. You can do it without disaeesmbling anything... pull the connector and stick a mutlimeter on it to check for continuity. Three poles, the center is the common... the switch should close on one of the other poles with the throttle closed and on the other at full throttle. Before doing ANYTHING else, verify that this is adjusted correctly.
Bill
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