High Idle???
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Joined: May 2008
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From: Roanoke Rapids NC
High Idle???
Ok I have a stock 85-- I have change out the EGR , ECM , TPS (53.6 ohms- the manual suggest 54 ohms), The IAC- which is set at 1 1/8, and of course the plugs, wires, distubor, coil, MAF and the O2 sensor.. My Idle runs between 8000 to 1100.. I have tried backing the idle screw out still no luck. Running out of idea's.. any help would be great... Thanks $300vett
oh ya check the ingectors 7 of the 8 has 16 ohms and 1 has 14ohms.. and can't find any vacum leaks...
oh ya check the ingectors 7 of the 8 has 16 ohms and 1 has 14ohms.. and can't find any vacum leaks...
Last edited by $300vett; Jun 27, 2008 at 12:51 PM.
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
Does it have the OEM PROM chip? It's possible that the Chip is commanding the idle speed you are getting. It's a guess.
Other than that, have you done the whole base idle setting thing? Warm motor, Ignition on, pin A/B connected at the ALDL (which will drive the IAC all the way shut, among everything else), unplug that IAC so that it Stays shut, start car and adjust the manual idle stop for 350-400 rpm idle (which probably won't work - shoot for the slowest the motor will reliably stay idling, whatever RPM that is). You can do it with the timing connector (EST Bypass) either unplugged or not - probably better to do it connected. Once the manual stop is adjusted you Then re-set the TPS adjustment to between .50 and .54 volts (the book says .54, plus or minus)
After all that, if it Still wants to idle fast, you need to use a scan tool to see what the ECM is getting for sensor inputs like coolant temp, MAT, and all of the others. Something has to be causing the ECM and PROM program to want the idle that high.
The only other possibility is a vacuum leak someplace. If the ECM has the IAC commanded closed, and the idle is still high, then air is getting in Someplace...
Other than that, have you done the whole base idle setting thing? Warm motor, Ignition on, pin A/B connected at the ALDL (which will drive the IAC all the way shut, among everything else), unplug that IAC so that it Stays shut, start car and adjust the manual idle stop for 350-400 rpm idle (which probably won't work - shoot for the slowest the motor will reliably stay idling, whatever RPM that is). You can do it with the timing connector (EST Bypass) either unplugged or not - probably better to do it connected. Once the manual stop is adjusted you Then re-set the TPS adjustment to between .50 and .54 volts (the book says .54, plus or minus)
After all that, if it Still wants to idle fast, you need to use a scan tool to see what the ECM is getting for sensor inputs like coolant temp, MAT, and all of the others. Something has to be causing the ECM and PROM program to want the idle that high.
The only other possibility is a vacuum leak someplace. If the ECM has the IAC commanded closed, and the idle is still high, then air is getting in Someplace...
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Joined: May 2008
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From: Roanoke Rapids NC
Thanks Rons85 Going to give it a try later today and will post the results....
Ok I pin the A/B connection and unplugged the IAC valve --at first it would not Idle-- adjusted the idle screw to 550 rpm.. set my TPS to .54volts, and pluged the IAC valve back up the idle went up to 700 to 900.. So l guess now where can I find a scan tool and is it simple to use???.
note-- when I change out the EGR valve I notice the MAT sensor was unplugged and I could not find it to plug it back up to the Plenum.. It looked like it has never been pluged in... The previous owner did not say anything about it--so I am clueless about it... and as far as the OEM PROM-- I know when I change out the ECM I put the same Proms back in????
I know this is confusing but all the help is greatly appreciated...
Will look again for the plug for the MAT sensor.......
Thanks $300vett
Ok I pin the A/B connection and unplugged the IAC valve --at first it would not Idle-- adjusted the idle screw to 550 rpm.. set my TPS to .54volts, and pluged the IAC valve back up the idle went up to 700 to 900.. So l guess now where can I find a scan tool and is it simple to use???.
note-- when I change out the EGR valve I notice the MAT sensor was unplugged and I could not find it to plug it back up to the Plenum.. It looked like it has never been pluged in... The previous owner did not say anything about it--so I am clueless about it... and as far as the OEM PROM-- I know when I change out the ECM I put the same Proms back in????
I know this is confusing but all the help is greatly appreciated...
Will look again for the plug for the MAT sensor.......
Thanks $300vett
Last edited by $300vett; Jun 28, 2008 at 05:01 PM.
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
If it Will idle down with the IAC shut and unhooked, then the ECM is Making it idle higher at whatever you get with everything connected.
That means the ECM is Commanding the 700-900 idle speed. That, in turn, means the PROM program sees a reason for that high an idle. The program may not be the OEM (non-factory chip), the ECM may be seeing something silly for coolant temp (thinks it's cold enough to raise the idle speeds), or something else - but it's the ECM doing it to you, and for a reason.
Maybe it thinks you are high pressure on the A/C system, or not standing still (mph reading) - could be any of several things.
You'll need a scan tool to see what the sensor readings (like the coolant temp) are, and if everything is right then you'll have to take a hard look at the chip...
BTW - in spite of what the book says I have found that an idle TPS setting of .50 or .52 is "better" than the .54, or higher. More reliable at settling into a solid idle speed at cold startup, etc. Could just be me, or the cam/timing I'm running, or who knows what.
That means the ECM is Commanding the 700-900 idle speed. That, in turn, means the PROM program sees a reason for that high an idle. The program may not be the OEM (non-factory chip), the ECM may be seeing something silly for coolant temp (thinks it's cold enough to raise the idle speeds), or something else - but it's the ECM doing it to you, and for a reason.
Maybe it thinks you are high pressure on the A/C system, or not standing still (mph reading) - could be any of several things.
You'll need a scan tool to see what the sensor readings (like the coolant temp) are, and if everything is right then you'll have to take a hard look at the chip...
BTW - in spite of what the book says I have found that an idle TPS setting of .50 or .52 is "better" than the .54, or higher. More reliable at settling into a solid idle speed at cold startup, etc. Could just be me, or the cam/timing I'm running, or who knows what.
Thread Starter
Advanced
Joined: May 2008
Posts: 72
Likes: 0
From: Roanoke Rapids NC
If it Will idle down with the IAC shut and unhooked, then the ECM is Making it idle higher at whatever you get with everything connected.
That means the ECM is Commanding the 700-900 idle speed. That, in turn, means the PROM program sees a reason for that high an idle. The program may not be the OEM (non-factory chip), the ECM may be seeing something silly for coolant temp (thinks it's cold enough to raise the idle speeds), or something else - but it's the ECM doing it to you, and for a reason.
Maybe it thinks you are high pressure on the A/C system, or not standing still (mph reading) - could be any of several things.
You'll need a scan tool to see what the sensor readings (like the coolant temp) are, and if everything is right then you'll have to take a hard look at the chip...
BTW - in spite of what the book says I have found that an idle TPS setting of .50 or .52 is "better" than the .54, or higher. More reliable at settling into a solid idle speed at cold startup, etc. Could just be me, or the cam/timing I'm running, or who knows what.
That means the ECM is Commanding the 700-900 idle speed. That, in turn, means the PROM program sees a reason for that high an idle. The program may not be the OEM (non-factory chip), the ECM may be seeing something silly for coolant temp (thinks it's cold enough to raise the idle speeds), or something else - but it's the ECM doing it to you, and for a reason.
Maybe it thinks you are high pressure on the A/C system, or not standing still (mph reading) - could be any of several things.
You'll need a scan tool to see what the sensor readings (like the coolant temp) are, and if everything is right then you'll have to take a hard look at the chip...
BTW - in spite of what the book says I have found that an idle TPS setting of .50 or .52 is "better" than the .54, or higher. More reliable at settling into a solid idle speed at cold startup, etc. Could just be me, or the cam/timing I'm running, or who knows what.
Thanks Rons85 I will try moving the TPS to .50 or so...
