88 vette with tpi, when setting min. idle the procedure calls for jumper in adl key on for 30 secs then unplug iac valve.I can hear the iac running when I do this but,It just sounds like a electric motor running.I thought that the iac was pushing the pintle into the seat during this procedure?My feeble memory seems to remember doing this on a tbi a long time ago and it sounding different?What should it sound like?
The IAC is a stepper motor. That is it can be though as having the rotor being a magnet surrounded by two electromagnetic coils. When one of the coils is energized, that will align the rotor to it's magnetic poles. To rotate the rotor, the other set of coils will be energized either a positive or negative polarity. Depending on the polarity, the rotor will either rotate clockwise or counter clockwise. The action is then repeated to obtain a continuous rotating motion.Originally Posted by tlfreak
Two advantages of the stepper motor is, you can keep count of the steps, and thus know where the pintle is, and when the pintle reaches a fully closed position, you can keep on energizing the electromagnets and it won't harm or burn out the motor.
The pintle is moved this way. Even after the pintle has reached it's seat, the ECM will continue to energize the magnets when the jumper is installed (key on engine off). It will sound like a buzzing, clicking or even like a running electric motor. That is normal.
If your engine's idle speed is being controlled by the ECM, you know the IAC motor is working. So if it starts with a higher idle when cold, and a lower idle when warm, it is working.
idle is high when cold lower when warm.The issue is between shifts(manual trans) idle is high 1400 to 1600 and very slow to return to lower idle
Does the idle return to normal with the car sitting after a while? ECMs are programmed to have a higher idle between shifts. When the ECM sees the vehicle stopped it drops the idle to the standard idle, assuming the engine is warm.
The throttle stop procedure is used to set the throttle body to keep the throttle open enough that the engine still idles (ie 500 rpm) when the IAC is totally closed. That is to keep the engine from stalling if the ECM is temporally screwed up and has the IAC setting too low. This might happen for example if you were coasting downhill for a long time with the throttle closed. The ECM will try to reduce the idle speed but going down hill has the engine turning higher than the target idle speed. So the ECM screws up and has the IAC closed too far and the engine would stall. So GM put the throttle stop screw to 'save' the engine at a minimum RPM so it doesn't stall.
That however doesn't sound anything like what your problem is.
Do you have a OBD1 scanner so you can look at what the ECM is doing?
A vacuum leak can cause a high idle. If your idle however does return to normal at some time then you don't have a vacuum leak however.
Do other 88 Vet owners have the same problem. ie is this a common problem with the programming in the ECM?
There is a possibility that the IAC is gummed up and closing slow also. IAC however seem to rarely fail.
It's supposed to do that, keeps idle high instead of a full deceleration causing emissions. Side effect is easier shift.
There are some TF Throttle Follower parameters that can be adjusted to tame it...
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
car has a mild 383 with a tune from the company that made the motor.I installed a prom from another used computer and it idled and returned to idle much better but the the prom was not for the same year vette as mine so the od control was all effed up! can scan with winadl but tunerpro rt won't connect,somebody said to try and adjust the baud rate in tunerpro to 8000?datalogs in winadl are hard to read.Would much rather be able to datalog in tunerpro if I could I would buy the stuff to try burning my own.
If you are using the correct .ADX file in TunerPro, there is no need to mess with the baud rate. Are you using the $32B.ADX? That is a 160 Baud pin E ECM.
I just tried again to connect with tunerpro I have the $32B.ADX still no connect tried different com ports no connect as always I exit tunerpro open winadl and I can see data and record but the winadl logs open in a word file thats unreadable.I'm going to look at the documentation that came with my usb cable then I am going on summits website to look at carbs
Your chip burner might have changed the code mask. There are several code masks that will run on the 1227165. Both the $32 and the $6D code masks are for a V8 and runs on the 1227165. You might want to try each of these .ADX files and see if either works.
http://www.gearhead-efi.com/Fuel-Inj...Information-32
http://www.gearhead-efi.com/Fuel-Inj...Information-6E
Years ago I could not get TunerPro RT to work on same PC that had WinALDL. Strange but true!
There's no reason to change Com posrts but you must have the correct one.
http://www.gearhead-efi.com/Fuel-Inj...to-TunerPro-RT
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
EagleMark thanks I did what was said in that link tunerpro found my cable said its working,when connected to car and started it says da connected at bottom and asks to name a file name for datalog even records but no data i open data dash no data I play back my recorded data no data maybe I have the wrong def. file? I'll try each one listed on this site for 165 ecm later when it's cooler out thanks for the help and patience everyone sorry I suck at computers so bad
you might try reinstalling tunerpro.
When you stop a datalog Windows will prompt you to save the data log file with a name.
If you did load the ADX data loging file first?
The 165 ECM is tricky and I think needs 10K on cable to start data flowing. Then disconnect 10K?
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
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