High IAC Counts
High IAC Counts Just put a cam in the car (mid 230's) and have very high IAC counts (150-160).
I adjusted the idle adjustment screw and did a TPS relearn. The guidance I have states to also monitor the TPS voltage, and verify that it doesn't exceed .6V for idle operation. I've adjusted the screw as far as I could to get the TPS voltage to .59V, and IAC counts dropped to 120-130.
I have not drilled the TB.
So here's my questions.
How important is that .4-.6V TPS voltage? If so, can the base range be changed in any table?
Should I drill my TB to get the counts down further?
Anything else I should set in HP Tuners?
Thanks.
I adjusted the idle adjustment screw and did a TPS relearn. The guidance I have states to also monitor the TPS voltage, and verify that it doesn't exceed .6V for idle operation. I've adjusted the screw as far as I could to get the TPS voltage to .59V, and IAC counts dropped to 120-130.
I have not drilled the TB.
So here's my questions.
How important is that .4-.6V TPS voltage? If so, can the base range be changed in any table?
Should I drill my TB to get the counts down further?
Anything else I should set in HP Tuners?
Thanks.
TECH Resident
Joined: Aug 2003
Posts: 970
Likes: 4
From: England UK
When you use the VCM scanner, is TPS showing 0%? this should verify that the PCM is seeing the voltage you expect. Wasn't sure how you were reading it, if you use a volt meter, then there may be slight variation to what the PCM is reading.
How high are your rev's? are they normal?
Have you adjusted the air flow table in the editor?
How high are your rev's? are they normal?
Have you adjusted the air flow table in the editor?
when i did my cam, we ran some calculations and drilled the TB and my IAC counts are 60~, keep in mind my car is the MANUAL CABLE NON COMPUTER DRIVEN TB. as in I can pop my hood and rev my motor by hand
Courtesy of Cpig's HP tuners manual, I had high IAC counts too until I followed this procedure.
SCAN:
• Now switch to a scanner that lets you see IAC counts and TPS voltage. This is where we will spend some time. We want IAC counts to be 40-60 for cars with aftermarket cams, and about 60-80 counts for stock cams.
ADJUST IAC:
• To reduce IAC counts turn off the car. Turn the idle set screw clockwise to open the throttle blade a LITTLE. Unplug the TPS, turn the key to the on position, DO NOT start the car, for 30 seconds. Turn the key off and plug TPS back in.
• Start the car and begin scanning. Monitor the IAC counts and repeat previous step until the IAC counts come into line. It will take about 4-6 times to get the IAC counts correct.
Note: Keep in mind that TPS voltage must be in the .4 to .6 range. If above or below this voltage, the PCM will fall into the wrong cell at idle. Check the TPS voltage each time the set screw is adjusted and adjust as necessary.
SCAN:
• Now switch to a scanner that lets you see IAC counts and TPS voltage. This is where we will spend some time. We want IAC counts to be 40-60 for cars with aftermarket cams, and about 60-80 counts for stock cams.
ADJUST IAC:
• To reduce IAC counts turn off the car. Turn the idle set screw clockwise to open the throttle blade a LITTLE. Unplug the TPS, turn the key to the on position, DO NOT start the car, for 30 seconds. Turn the key off and plug TPS back in.
• Start the car and begin scanning. Monitor the IAC counts and repeat previous step until the IAC counts come into line. It will take about 4-6 times to get the IAC counts correct.
Note: Keep in mind that TPS voltage must be in the .4 to .6 range. If above or below this voltage, the PCM will fall into the wrong cell at idle. Check the TPS voltage each time the set screw is adjusted and adjust as necessary.
150 is not excessively high, it's right about center.
If you want it to come down, don't screw with the
blade stop or drilling, get the idle-range mixture
and spark cleaned up from what the cam did to it.
The cleaner it idles the less air it needs.
If you want it to come down, don't screw with the
blade stop or drilling, get the idle-range mixture
and spark cleaned up from what the cam did to it.
The cleaner it idles the less air it needs.
I should mention the car is a 2000 TransAm. Sometime I take it for granted which car I'm modding and forget to let others know when asking for help.
I'll have to verify what % the TPS was at. In the Scanner, you can select TPS Voltage to monitor that directly, it was not done through a volt meter.
I have the idle range set at around 850RPM......it goes higher as ECT's go colder. Plus the AC on and in/gear settings are a bit higher as well.
I adjusted the idle airflow vs. ECT table. But to be quite honest, didn't know exactly how much to modify it. If you have some guidance, that would be helpful.
Yes, I have the same cable driven TB. What calculations did you run?
Thank you.
That's the exact procedure I was following.
How do you recommend zeroing in on the idle mixture.
Other than that, I have no idleing issues that are troublesome. Car idles well and maintains it, not too much fluctuation. The only issues I have are low RPM in gear performance, where there is some slight surging and idle fluctuation, but I believe the stock TC is the culprut and my SS3600 is on the way. BTW, anything to adjust for the new stall?
When you use the VCM scanner, is TPS showing 0%? this should verify that the PCM is seeing the voltage you expect. Wasn't sure how you were reading it, if you use a volt meter, then there may be slight variation to what the PCM is reading.
How high are your rev's? are they normal?
Have you adjusted the air flow table in the editor?
How high are your rev's? are they normal?
Have you adjusted the air flow table in the editor?
I have the idle range set at around 850RPM......it goes higher as ECT's go colder. Plus the AC on and in/gear settings are a bit higher as well.
I adjusted the idle airflow vs. ECT table. But to be quite honest, didn't know exactly how much to modify it. If you have some guidance, that would be helpful.
Courtesy of Cpig's HP tuners manual, I had high IAC counts too until I followed this procedure.
SCAN:
• Now switch to a scanner that lets you see IAC counts and TPS voltage. This is where we will spend some time. We want IAC counts to be 40-60 for cars with aftermarket cams, and about 60-80 counts for stock cams.
ADJUST IAC:
• To reduce IAC counts turn off the car. Turn the idle set screw clockwise to open the throttle blade a LITTLE. Unplug the TPS, turn the key to the on position, DO NOT start the car, for 30 seconds. Turn the key off and plug TPS back in.
• Start the car and begin scanning. Monitor the IAC counts and repeat previous step until the IAC counts come into line. It will take about 4-6 times to get the IAC counts correct.
Note: Keep in mind that TPS voltage must be in the .4 to .6 range. If above or below this voltage, the PCM will fall into the wrong cell at idle. Check the TPS voltage each time the set screw is adjusted and adjust as necessary.
SCAN:
• Now switch to a scanner that lets you see IAC counts and TPS voltage. This is where we will spend some time. We want IAC counts to be 40-60 for cars with aftermarket cams, and about 60-80 counts for stock cams.
ADJUST IAC:
• To reduce IAC counts turn off the car. Turn the idle set screw clockwise to open the throttle blade a LITTLE. Unplug the TPS, turn the key to the on position, DO NOT start the car, for 30 seconds. Turn the key off and plug TPS back in.
• Start the car and begin scanning. Monitor the IAC counts and repeat previous step until the IAC counts come into line. It will take about 4-6 times to get the IAC counts correct.
Note: Keep in mind that TPS voltage must be in the .4 to .6 range. If above or below this voltage, the PCM will fall into the wrong cell at idle. Check the TPS voltage each time the set screw is adjusted and adjust as necessary.
That's the exact procedure I was following.
Other than that, I have no idleing issues that are troublesome. Car idles well and maintains it, not too much fluctuation. The only issues I have are low RPM in gear performance, where there is some slight surging and idle fluctuation, but I believe the stock TC is the culprut and my SS3600 is on the way. BTW, anything to adjust for the new stall?
12 Second Club
Joined: Apr 2002
Posts: 680
Likes: 0
From: Cave Creek, AZ- Canada Also.
I'm not sure why people insist on this range of .4 to .6 volts for closed Throttle. Here's what GM says.
The Throttle Position (TP) sensor is connected to
the throttle shaft on the throttle body unit. It is a
potentiometer with one end connected to 5 volts
from the PCM and the other end to PCM earth. A
third wire connects from a sliding contact in the TP
sensor to the PCM allowing the PCM to measure
the voltage from the TP sensor. As the throttle is
moved (accelerator pedal moved), the output of the
TP sensor changes. At a closed throttle position,
the output of the TP sensor is below 1.25V. As the
throttle valve opens, the output increases so that,
at wide-open throttle (WOT), the output voltage
should be about 4 volts.
By monitoring the output voltage from the TP
sensor, the PCM can determine fuel delivery based
on throttle valve angle (driver demand). A broken
or loose TP sensor can cause intermittent bursts of
fuel from the injectors, and an unstable idle,
because the PCM interprets the throttle is moving.
The TP sensor is not adjustable and there is no set
value for voltage at closed throttle because the
actual voltage at closed throttle can vary from
vehicle to vehicle due to tolerances. The PCM has
a special program built into it that can adjust for the
tolerances in the TP sensor voltage reading at idle.
The PCM uses the reading at closed throttle idle
for the zero reading (0% throttle) so no adjustment
is necessary. Even if the TP sensor voltage
reading was to be changed by: tampering, throttle
body coking, sticking cable or any other reason,
the TP sensor will still be 0%. The PCM will learn
what the closed throttle value is every time the
throttle comes back to closed throttle.
The Throttle Position (TP) sensor is connected to
the throttle shaft on the throttle body unit. It is a
potentiometer with one end connected to 5 volts
from the PCM and the other end to PCM earth. A
third wire connects from a sliding contact in the TP
sensor to the PCM allowing the PCM to measure
the voltage from the TP sensor. As the throttle is
moved (accelerator pedal moved), the output of the
TP sensor changes. At a closed throttle position,
the output of the TP sensor is below 1.25V. As the
throttle valve opens, the output increases so that,
at wide-open throttle (WOT), the output voltage
should be about 4 volts.
By monitoring the output voltage from the TP
sensor, the PCM can determine fuel delivery based
on throttle valve angle (driver demand). A broken
or loose TP sensor can cause intermittent bursts of
fuel from the injectors, and an unstable idle,
because the PCM interprets the throttle is moving.
The TP sensor is not adjustable and there is no set
value for voltage at closed throttle because the
actual voltage at closed throttle can vary from
vehicle to vehicle due to tolerances. The PCM has
a special program built into it that can adjust for the
tolerances in the TP sensor voltage reading at idle.
The PCM uses the reading at closed throttle idle
for the zero reading (0% throttle) so no adjustment
is necessary. Even if the TP sensor voltage
reading was to be changed by: tampering, throttle
body coking, sticking cable or any other reason,
the TP sensor will still be 0%. The PCM will learn
what the closed throttle value is every time the
throttle comes back to closed throttle.
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As Jimmy stated, getting the fueling and spark optimal, the engine will require less throttle angle to achieve the desired idle.
Alot of times I have to do the same, crank the throttle open at first, then deal with the idle being kinda crappy while I dial in the VE, get the spark tables in line (I have a base I usually start from for those) and then alot of times, I'll have to back the throttle back down.
BTW, it would help if you posted your tune.
Alot of times I have to do the same, crank the throttle open at first, then deal with the idle being kinda crappy while I dial in the VE, get the spark tables in line (I have a base I usually start from for those) and then alot of times, I'll have to back the throttle back down.
BTW, it would help if you posted your tune.
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