IAC problems
01-28-2017, 05:13 PM
#1
Registered User
Thread Starter
Join Date: May 2006
Location: Kingsport,TN
Posts: 247
IAC problems
I can't seem to figure out the problem on the IAC. Upon start up it's maxing out at 160 and doesn't want to take any throttle. And will creep down to around 130 -120.
Some of the things I've done :
1. Played with the Idle adj. screw. ( still high)
2.Sprayed starting fluid around the intake no spike in the idle.
3. Took the TB apart cleaned it put all new gasket's on it (still no change)
4. Checked the resistance on the IAC I was getting 50 ohms (in range)
5. Reset the IAC position (no change)
The only thing that has changed is when I had the motor rebuilt it had to be bored .30 .I have talked to Solomon he seems to think it need's to be updated but need to figure out the IAC problem first.
I am out of ideal's with what to do.
Some of the things I've done :
1. Played with the Idle adj. screw. ( still high)
2.Sprayed starting fluid around the intake no spike in the idle.
3. Took the TB apart cleaned it put all new gasket's on it (still no change)
4. Checked the resistance on the IAC I was getting 50 ohms (in range)
5. Reset the IAC position (no change)
The only thing that has changed is when I had the motor rebuilt it had to be bored .30 .I have talked to Solomon he seems to think it need's to be updated but need to figure out the IAC problem first.
I am out of ideal's with what to do.
01-28-2017, 07:26 PM
#2
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,650
Re: IAC problems
Does it idle where it's programmed to idle? Does the idle start out high and then gradually drop down as the engine warms up, and the IAC counts drop?
The "counts" shown on the scanner are what the PCM is telling the valve to do. No feedback on whether the the valve is doing what it is told to do.
When you adjusted the throttle stop, did the counts drop as you opened the blades?
The "counts" shown on the scanner are what the PCM is telling the valve to do. No feedback on whether the the valve is doing what it is told to do.
When you adjusted the throttle stop, did the counts drop as you opened the blades?
01-28-2017, 08:36 PM
#3
Registered User
Thread Starter
Join Date: May 2006
Location: Kingsport,TN
Posts: 247
Re: IAC problems
Does it idle where it's programmed to idle? Does the idle start out high and then gradually drop down as the engine warms up, and the IAC counts drop?
The "counts" shown on the scanner are what the PCM is telling the valve to do. No feedback on whether the the valve is doing what it is told to do.
When you adjusted the throttle stop, did the counts drop as you opened the blades?
The "counts" shown on the scanner are what the PCM is telling the valve to do. No feedback on whether the the valve is doing what it is told to do.
When you adjusted the throttle stop, did the counts drop as you opened the blades?
Yeah a little then I tried to get them on down and it had the idle way to high
01-28-2017, 09:54 PM
#4
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,650
Re: IAC problems
When the engine is fully warmed up, and it's idling high, does the scanner indicate:
- the TPS voltage is less than 0.90 volts, and/or the throttle percent is 0%.
- the vehicle speed is 0.
If either of those conditions is not met, the PCM may increase the idle counts.
- what is the coolant temp sensor reading in the PCM? Is it above 150*F?
Lower temperatures cause the PCM to raise the idle speed.
- the TPS voltage is less than 0.90 volts, and/or the throttle percent is 0%.
- the vehicle speed is 0.
If either of those conditions is not met, the PCM may increase the idle counts.
- what is the coolant temp sensor reading in the PCM? Is it above 150*F?
Lower temperatures cause the PCM to raise the idle speed.
01-29-2017, 11:35 AM
#5
Registered User
Thread Starter
Join Date: May 2006
Location: Kingsport,TN
Posts: 247
Re: IAC problems
The TPS voltage is 0.80 with the throttle present is at 0%.
The CST was 73.2c when it warmed up.
Do you think I could be out of time by a tooth either way? I have been thinking about that a lot.
The CST was 73.2c when it warmed up.
Do you think I could be out of time by a tooth either way? I have been thinking about that a lot.
01-29-2017, 04:55 PM
#6
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,650
Re: IAC problems
The things that stand out in that single frame of data is the very high MAP (60 kPa) and the very high MAF flow (14.5 g/sec). The CC503 accounts in part for the high MAP (low vacuum), but maybe not all of it. And I'm used to seeing 6 to 10 g/sec at 750 RPM idle.
There's also 1-degree of knock retard, which should not be there at idle, unless it's the 1.6X full roller rockers. Do you have an LT4 knock module? Or maybe you're on to something with the cam timing being off.
There's also 1-degree of knock retard, which should not be there at idle, unless it's the 1.6X full roller rockers. Do you have an LT4 knock module? Or maybe you're on to something with the cam timing being off.
01-29-2017, 06:34 PM
#7
Registered User
Thread Starter
Join Date: May 2006
Location: Kingsport,TN
Posts: 247
Re: IAC problems
The idle will vary from as low as 600 to as high as 850 and I don't have a LT4 KM.I have seen the knock retard as high as 4 on idle I'm going to tear back into in just to make sure it's in time.