1986 Base Idle Adjustment
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 1,037
Likes: 28
From: Montclair New Jersey
1986 Base Idle Adjustment
I know this has been explained many times but.....I have read and have been told at least ten different ways of adjusting the base idle. Do you unplug the IAC and or the ECT? If someone has the correct procedure it would be greatly apprectiated.
Thanks
Thanks
Team Owner
Joined: Jul 2004
Posts: 28,353
Likes: 3,253
From: Hartford WI
If you don't know what the idle speed is, ask. Don't assume. Get yourself a scanner and see what the idle speed should be based on what the ECM wants.
The official way to do it is wonderful IF you want to make assumptions. I would, and do, forget that entire thing and check things before throwing parts at it. Are you sure that the timing is right? Make sure the harmonic balancer is not moving on you. After all these years, IF it is original, it might. If it does, your timing will probably be wrong. If that is wrong, setting the timing is difficult. TEST for good balancer. If the balancer is right and the timing is at 6 degrees, check the fuel pressure. Does it spike up to the right numbers? Does it hold pressure after shut off? If so, time to move on to other things. Plugs and wires, cap and rotor. If those are good get yourself a scanner. You will need it sooner or later. Not a code reader, a scanner where you can see live data.
With a scanner, you can see what the ECM wants the idle to be and not what we say. Run the motor it for a while and let it get to closed loop and operating temperature. With everything but the motor off, check what the ECM wants at this point and see what the ECM says the rpm is. Your tach could be inaccurate and IIRC, they often are. Check what the IAC counts are. IF they are higher than 30, the ECM is asking for more air. Turn the adjustment screw in to open the blades. Rev and check again after it settles down. If it is lower, turn it out to close the blades. Now if it is 0 and you can't do anything about it, you have an air leak. Once that is set to 30 counts, give or take a few, you are done. The TPS can now be set.
The official way to do it is wonderful IF you want to make assumptions. I would, and do, forget that entire thing and check things before throwing parts at it. Are you sure that the timing is right? Make sure the harmonic balancer is not moving on you. After all these years, IF it is original, it might. If it does, your timing will probably be wrong. If that is wrong, setting the timing is difficult. TEST for good balancer. If the balancer is right and the timing is at 6 degrees, check the fuel pressure. Does it spike up to the right numbers? Does it hold pressure after shut off? If so, time to move on to other things. Plugs and wires, cap and rotor. If those are good get yourself a scanner. You will need it sooner or later. Not a code reader, a scanner where you can see live data.
With a scanner, you can see what the ECM wants the idle to be and not what we say. Run the motor it for a while and let it get to closed loop and operating temperature. With everything but the motor off, check what the ECM wants at this point and see what the ECM says the rpm is. Your tach could be inaccurate and IIRC, they often are. Check what the IAC counts are. IF they are higher than 30, the ECM is asking for more air. Turn the adjustment screw in to open the blades. Rev and check again after it settles down. If it is lower, turn it out to close the blades. Now if it is 0 and you can't do anything about it, you have an air leak. Once that is set to 30 counts, give or take a few, you are done. The TPS can now be set.
Last edited by aklim; Jul 18, 2021 at 11:56 PM.
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 1,037
Likes: 28
From: Montclair New Jersey
If you don't know what the idle speed is, ask. Don't assume. Get yourself a scanner and see what the idle speed should be based on what the ECM wants.
The official way to do it is wonderful IF you want to make assumptions. I would, and do, forget that entire thing and check things before throwing parts at it. Are you sure that the timing is right? Make sure the harmonic balancer is not moving on you. After all these years, IF it is original, it might. If it does, your timing will probably be wrong. If that is wrong, setting the timing is difficult. TEST for good balancer. If the balancer is right and the timing is at 6 degrees, check the fuel pressure. Does it spike up to the right numbers? Does it hold pressure after shut off? If so, time to move on to other things. Plugs and wires, cap and rotor. If those are good get yourself a scanner. You will need it sooner or later. Not a code reader, a scanner where you can see live data.
With a scanner, you can see what the ECM wants the idle to be and not what we say. Run the motor it for a while and let it get to closed loop and operating temperature. With everything but the motor off, check what the ECM wants at this point and see what the ECM says the rpm is. Your tach could be inaccurate and IIRC, they often are. Check what the IAC counts are. IF they are higher than 30, the ECM is asking for more air. Turn the adjustment screw in to open the blades. Rev and check again after it settles down. If it is lower, turn it out to close the blades. Now if it is 0 and you can't do anything about it, you have an air leak. Once that is set to 30 counts, give or take a few, you are done. The TPS can now be set.
The official way to do it is wonderful IF you want to make assumptions. I would, and do, forget that entire thing and check things before throwing parts at it. Are you sure that the timing is right? Make sure the harmonic balancer is not moving on you. After all these years, IF it is original, it might. If it does, your timing will probably be wrong. If that is wrong, setting the timing is difficult. TEST for good balancer. If the balancer is right and the timing is at 6 degrees, check the fuel pressure. Does it spike up to the right numbers? Does it hold pressure after shut off? If so, time to move on to other things. Plugs and wires, cap and rotor. If those are good get yourself a scanner. You will need it sooner or later. Not a code reader, a scanner where you can see live data.
With a scanner, you can see what the ECM wants the idle to be and not what we say. Run the motor it for a while and let it get to closed loop and operating temperature. With everything but the motor off, check what the ECM wants at this point and see what the ECM says the rpm is. Your tach could be inaccurate and IIRC, they often are. Check what the IAC counts are. IF they are higher than 30, the ECM is asking for more air. Turn the adjustment screw in to open the blades. Rev and check again after it settles down. If it is lower, turn it out to close the blades. Now if it is 0 and you can't do anything about it, you have an air leak. Once that is set to 30 counts, give or take a few, you are done. The TPS can now be set.
thanks again.
Team Owner
Joined: Jul 2004
Posts: 28,353
Likes: 3,253
From: Hartford WI
You could. I am not totally sure since I don't get into tuning myself so I don't really know what to use and how good they are. I usually have programs to datalong which I seldom use. Most of the time, it is there to read data onto the phone. That is the part I am talking about. Scanning data. I use the phone apps not windows apps
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 1,037
Likes: 28
From: Montclair New Jersey
Ok I never tried scanning through an App before. I'm assuming I need a cable that would communicate with the car to my Android phone. What App is best to use and where would I get the cable.
Thanks again
Thanks again
Pro
Joined: Feb 2009
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From: Vancouver Washington
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Team Owner
Joined: Jul 2004
Posts: 28,353
Likes: 3,253
From: Hartford WI
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 1,037
Likes: 28
From: Montclair New Jersey
I see the APPs to use but; I'm not sure on which ADX file to download. I have a 1986 and with a 1227165 ECM. Some of the files don't list a 1986. They start at 1989. Any ideas on how to figure out which file I need.
Thanks again.
Thanks again.
Pro
Joined: Aug 2020
Posts: 646
Likes: 125
From: Liliha Bakery stuffing my face with coco puffs!
A028*...in ALDLDroid lumps l98 '85-'88 together. Don't know that it would work considering '85 is a different ecm from the latter and the different masks.
Last edited by stew86MCSS396; Jul 29, 2021 at 10:56 PM.
Melting Slicks
Joined: Aug 2003
Posts: 3,380
Likes: 388
From: Lakeville MI
A028 is only 160 baud which is not what you want for this purpose since the idle will be set to 1000 rpm via the ALDL idle rpm (unless this has been reprogrammed to the normal desired idle rpm) Note: this method could be an option for you if you're programming/tuning and stuck with 160 baud logging.
A059 is 8192 baud and the datastream is close enough for what you are doing.
Unfortunately,1986 cars can be problematic logging at 8192 baud. Some applications are better than others Diacom and DataCat are known to work well with 8192 baud logging with 1986 cars/bins.
As already mentioned, the datastreams are close enough between 86, 87-88 and 89, but the problem will be connecting. Changes were made to the serial data initialization routine after 1986 making it easier to connect with the later year cars. I've re-written a few 1986 bin files to correct this issue. You many need to use a newer memcal or reprogram to use a newer bin file.
What bin is in the car now? Also Auto or 4+3? Auto trans makes for an easier upgrade to a newer bin if applicable. 4+3 requires some additional work-arounds to retain shifter switch functionality but can be done.
If I have some time, I will try and see if I can connect at 8192 baud with a 1986 bin file running in my own 1988 car with ALDLdroid (wired connection). I'm not optimistic, but might be in for a surprise. Sorry, I can't test with ALDL Scan since I don't have the bluetooth adapter. Maybe somebody else can volunteer to test it with an 86 bin file and/or 1986 car.
A laptop with DataCat may be your best bet.
A059 is 8192 baud and the datastream is close enough for what you are doing.
Unfortunately,1986 cars can be problematic logging at 8192 baud. Some applications are better than others Diacom and DataCat are known to work well with 8192 baud logging with 1986 cars/bins.
As already mentioned, the datastreams are close enough between 86, 87-88 and 89, but the problem will be connecting. Changes were made to the serial data initialization routine after 1986 making it easier to connect with the later year cars. I've re-written a few 1986 bin files to correct this issue. You many need to use a newer memcal or reprogram to use a newer bin file.
What bin is in the car now? Also Auto or 4+3? Auto trans makes for an easier upgrade to a newer bin if applicable. 4+3 requires some additional work-arounds to retain shifter switch functionality but can be done.
If I have some time, I will try and see if I can connect at 8192 baud with a 1986 bin file running in my own 1988 car with ALDLdroid (wired connection). I'm not optimistic, but might be in for a surprise. Sorry, I can't test with ALDL Scan since I don't have the bluetooth adapter. Maybe somebody else can volunteer to test it with an 86 bin file and/or 1986 car.
A laptop with DataCat may be your best bet.
Last edited by tequilaboy; Jul 31, 2021 at 08:49 AM.
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 1,037
Likes: 28
From: Montclair New Jersey
A028 is only 160 baud which is not what you want for this purpose since the idle will be set to 1000 rpm via the ALDL idle rpm (unless this has been reprogrammed to the normal desired idle rpm) Note: this method could be an option for you if you're programming/tuning and stuck with 160 baud logging.
A059 is 8192 baud and the datastream is close enough for what you are doing.
Unfortunately,1986 cars can be problematic logging at 8192 baud. Some applications are better than others Diacom and DataCat are known to work well with 8192 baud logging with 1986 cars/bins.
As already mentioned, the datastreams are close enough between 86, 87-88 and 89, but the problem will be connecting. Changes were made to the serial data initialization routine after 1986 making it easier to connect with the later year cars. I've re-written a few 1986 bin files to correct this issue. You many need to use a newer memcal or reprogram to use a newer bin file.
What bin is in the car now? Also Auto or 4+3? Auto trans makes for an easier upgrade to a newer bin if applicable. 4+3 requires some additional work-arounds to retain shifter switch functionality but can be done.
If I have some time, I will try and see if I can connect at 8192 baud with a 1986 bin file running in my own 1988 car with ALDLdroid (wired connection). I'm not optimistic, but might be in for a surprise. Sorry, I can't test with ALDL Scan since I don't have the bluetooth adapter. Maybe somebody else can volunteer to test it with an 86 bin file and/or 1986 car.
A laptop with DataCat may be your best bet.
A059 is 8192 baud and the datastream is close enough for what you are doing.
Unfortunately,1986 cars can be problematic logging at 8192 baud. Some applications are better than others Diacom and DataCat are known to work well with 8192 baud logging with 1986 cars/bins.
As already mentioned, the datastreams are close enough between 86, 87-88 and 89, but the problem will be connecting. Changes were made to the serial data initialization routine after 1986 making it easier to connect with the later year cars. I've re-written a few 1986 bin files to correct this issue. You many need to use a newer memcal or reprogram to use a newer bin file.
What bin is in the car now? Also Auto or 4+3? Auto trans makes for an easier upgrade to a newer bin if applicable. 4+3 requires some additional work-arounds to retain shifter switch functionality but can be done.
If I have some time, I will try and see if I can connect at 8192 baud with a 1986 bin file running in my own 1988 car with ALDLdroid (wired connection). I'm not optimistic, but might be in for a surprise. Sorry, I can't test with ALDL Scan since I don't have the bluetooth adapter. Maybe somebody else can volunteer to test it with an 86 bin file and/or 1986 car.
A laptop with DataCat may be your best bet.
My 86 is an automatic. Thanks for the help