so when I start the car from cold I am not getting the normal fast idle where it will idle at say 1200-1500 rpm or whatever until coolant temp comes up. It does for like 3 or 4 seconds and drops to normal warm idle speed. I have cleaned IAC checked TPS (it's at 1.2v) and cleaned the MAF sensor. I will be replacing the ECT sensor in the next couple of days. Anyone else experienced this?This is the first time I think I have ever had this happen on a car. I would like to have the fast idle back for warming the car up a few minutes on cold days this winter. thanks for any help!
Car has no "fast idle" at cold startup?
- Thread starter 9646gt
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ttocs
Forum's #1 poster
1.2v? I thought it was supposed to be around 1 or less?
There are two tables that determine the idle at startup. These are commanded by the ECU programed parameters. One is the coolant temp vs. idle table and the second is the idle vs. time table. The first is determined by the ECT sensor signal and the second is just a decay based on time usually about 5 seconds. If the ECT signal is read as warm then only the decay table is at play which from your description appears to be the case.
Awesome I will replace ect sensor this weekend. I think the 1.2 volts on the TPS wis in the good range for our model years. Also I have been told leaving KOEO for 20 plus seconds zeros the TPS in the ECU and make adjustment pretty irrelevant but not sure how true it is really. The previous owner did adjsut the throttle stop screw to raise idle some to compensate for the low charging and less cooling due to UDP's being installed.
Adjusting the throttle stop screw will affect the TPS voltage and is self defeating as the idle speed is commanded by the ECU. The adaptive strategy allows the ECU to learn the voltage at idle within the expected range of .65v-1.25. The mid point being about .95v.
So until I get an SCT chip and can change the idle speed that way, how can I raise the idle to keep proper charging and cooling with my UDPs? I will be installing a brand new summit 70mm tb with explorer intake today so it should have a proper idle screw. Do I set the idle where I want at normal themp then adjust tps so the voltage is back down around .95? Or will the ECU still over ride this somehow? Also I will be replacing the ect today to see if it fixes fast idle. Tony, when it's cold out does your car have a fast idle?
The throttle set screw on the new TB is preset and shouldn't need to be touched. UDP's by and large don't have a big affect on the water pump and alternator as they are usually larger than stock to compensate for the smaller crank pulley. If there is an issue it's usually because only the smaller crank pulley was installed. If the car idles well from cold to warm there is nothing to fix.
