Low Idle
11-24-2012, 12:50 PM
#11
2nd Gear Member
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Join Date: Jul 2011
Location: Indiana
Posts: 414
Looks like I was supposed to use an allen wrench. Well that would have made it considerably easier. For a smart person I do have my dumb moments.
I did not follow the process you outlined to a T. I figured since my idle was too low, I simply needed to open the throttle plate a bit more. I just turned the screw until the idle was where I wanted it to be. Will this method cause problems? I suppose it's not too late to pick up a feeler guage and do it exactly as outlined. Should be a LOT easier with an allen wrench. haha
I did not follow the process you outlined to a T. I figured since my idle was too low, I simply needed to open the throttle plate a bit more. I just turned the screw until the idle was where I wanted it to be. Will this method cause problems? I suppose it's not too late to pick up a feeler guage and do it exactly as outlined. Should be a LOT easier with an allen wrench. haha
11-24-2012, 01:01 PM
#12
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Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Using the feeler gauge and then turning the screw in one turn is the correct way to preset the TB throttle plate. Remember this is not adjusting the idle, the PCM does that as uber' described earlier.
What you are doing here is setting the air bleed through the throttle so that the PCM can then control the IAC to both increase and decrease total air flow above/below the preset bleed as needed to control the idle properly...
What you are doing here is setting the air bleed through the throttle so that the PCM can then control the IAC to both increase and decrease total air flow above/below the preset bleed as needed to control the idle properly...
11-24-2012, 06:17 PM
#15
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Location: Saint Augustine, FL
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IT is OK to tighten the TB stop screw a bit, up to 1/2 to 3/4 turn if needed to get the idle stable--especially with an aftermarket TB.
The TPS is easy to test, connect a voltmeter across the gray/white (+ lead) and gray/red wires. With the Key On and Engine Off (KOEO) the voltage should track the charts below as you open and close the throttle slowly. The voltage should rise and fall smoothly with no dropouts or spikes:
The TPS does not need to be adjusted, nor is it adjustable; if the voltages track as shown on the charts, and smoothly and steadily, the TPS is OK.
From the shop manual:
The TPS is easy to test, connect a voltmeter across the gray/white (+ lead) and gray/red wires. With the Key On and Engine Off (KOEO) the voltage should track the charts below as you open and close the throttle slowly. The voltage should rise and fall smoothly with no dropouts or spikes:
The TPS does not need to be adjusted, nor is it adjustable; if the voltages track as shown on the charts, and smoothly and steadily, the TPS is OK.
From the shop manual:
Idle Speed Control Closed Throttle Determination
One of the fundamental criteria for entering rpm control is an indication of closed throttle. Throttle mode is always calculated to the lowest learned throttle position (TP) voltage seen since engine start. This lowest learned value is called "ratch," since the software acts like a one-way ratch.
The ratch value (voltage) is displayed as the TPREL PID. The ratch value is relearned after every engine start. Ratch will learn the lowest, steady TP voltage seen after the engine starts. In some cases, ratch can learn higher values of TP. The time to learn the higher values is significantly longer than the time to learn the lower values. The brakes must also be applied to learn the longer values.
All PCM functions are done using this ratch voltage, including idle speed control. The PCM goes into closed throttle mode when the TP voltage is at the ratch (TPREL PID) value. Increase in TP voltage, normally less than 0.05 volts, will put the PCM in part throttle mode. Throttle mode can be viewed by looking at the TP MODE PID. With the throttle closed, the PID must read C/T (closed throttle). Slightly corrupt values of ratch can prevent the PCM from entering closed throttle mode.
An incorrect part throttle indication at idle will prevent entry into closed throttle rpm control, and could result in a high idle. Ratch can be corrupted by a throttle position sensor or circuit that "drops out" or is noisy, or by loose/worn throttle plates that close tight during a decel and spring back at a normal engine vacuum
One of the fundamental criteria for entering rpm control is an indication of closed throttle. Throttle mode is always calculated to the lowest learned throttle position (TP) voltage seen since engine start. This lowest learned value is called "ratch," since the software acts like a one-way ratch.
The ratch value (voltage) is displayed as the TPREL PID. The ratch value is relearned after every engine start. Ratch will learn the lowest, steady TP voltage seen after the engine starts. In some cases, ratch can learn higher values of TP. The time to learn the higher values is significantly longer than the time to learn the lower values. The brakes must also be applied to learn the longer values.
All PCM functions are done using this ratch voltage, including idle speed control. The PCM goes into closed throttle mode when the TP voltage is at the ratch (TPREL PID) value. Increase in TP voltage, normally less than 0.05 volts, will put the PCM in part throttle mode. Throttle mode can be viewed by looking at the TP MODE PID. With the throttle closed, the PID must read C/T (closed throttle). Slightly corrupt values of ratch can prevent the PCM from entering closed throttle mode.
An incorrect part throttle indication at idle will prevent entry into closed throttle rpm control, and could result in a high idle. Ratch can be corrupted by a throttle position sensor or circuit that "drops out" or is noisy, or by loose/worn throttle plates that close tight during a decel and spring back at a normal engine vacuum
11-25-2012, 10:24 AM
#16
2nd Gear Member
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Join Date: Jul 2011
Location: Indiana
Posts: 414
Hmm, perhaps I'll borrow my dad's voltmeter sometime and give that a try. I did notice that despite the same lower idle I had before, after adjusting the idle screw properly it is idleing noticeably smoother.
11-25-2012, 10:56 AM
#18
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Join Date: Jul 2011
Location: Indiana
Posts: 414
Yeah, I haven't had the cash to pick up a tuner or anything yet, so I'm just going by the stock tach. I knew it wasn't that accurate, but when I was looking online, people said theirs idled closer to 800 or 900. I suppose they were mistaken. Since you say the idle is closer to 700, then it's probably idleing right where it should be.
Hopefully it keeps up with the smoother idle. Sometimes it behaves better than others, so it may have just been behaving nicely last night.
Hopefully it keeps up with the smoother idle. Sometimes it behaves better than others, so it may have just been behaving nicely last night.
11-25-2012, 11:46 AM
#19
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Join Date: Dec 2006
Location: Saint Augustine, FL
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Your PCM boxcode is likely XHS2, the RYAF1 strategy, same as my '03. The stock idle is 736 rpm as I said above; I've not seen a stock tune with the idle as high as 800 to 900 rpm, here are some examples from a few tunes selected at random:
Go figure...
- 680 in CRAJ0.AOL3;
- 625 in FMAG0.RMR0;
- 736 in FBFG2.RKN2;
- 680 in RYAF1.MDE3;
- 736 in RYAF1.XSH2;
- 640 in RYBE2.YDH1;
- 720 in RVAFA.NUX2;
- 640 in RZAO1,BMD0;
- 705 in RVAF1.KSG0;
Go figure...
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