EST and timing
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,460
Likes: 48
EST and timing
Hello Everybody, I am working on my 1985 4 plus 3. When you are setting the timing. You disconnect the EST. When you are done and plug the EST back in what happens or should happen to the timing. Does it advance/retard. If I accelerate the engine the timing should advance correct. Thank you all
We set the idle and timing. When we accelerated the engine the timing did not advance. Any and all ideas are welcomed.
We set the idle and timing. When we accelerated the engine the timing did not advance. Any and all ideas are welcomed.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
I'm pretty sure it will immediately advance soon as you reconnect the EST.
Yes the ECM advances timing with engine rpm as the plugs need fire earlier as engine speed increases because the speed of the flame front is (relatively) constant.
Yes the ECM advances timing with engine rpm as the plugs need fire earlier as engine speed increases because the speed of the flame front is (relatively) constant.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,460
Likes: 48
Thank you. The general consensus is that the timing should advance when the EST is connected. And definitely when the car is throttled. We are going to pull the cap and make sure all of the wires are good.
Thanks again
Thanks again
Drifting
Joined: Jun 2018
Posts: 1,402
Likes: 287
From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
On an 84 nothing happens when you plug the EST back in until you turn the ignition off then back on. Then the ECM handles the timing. I thought the 85 was the same.
Le Mans Master
Joined: Aug 2017
Posts: 6,930
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From: New Jersey
With the est disconnected throttle should still advance the timing a little. Confirm that first. Takes 1500 rpm or so to do it.
On a restart timing should run in base for a period of time (est connected) then the computer should advance it. With the wire connected timing at idle should be beyond the timing marks.
Sounds like something isn't working. Do you get a check engine light with the est wire off?
On a restart timing should run in base for a period of time (est connected) then the computer should advance it. With the wire connected timing at idle should be beyond the timing marks.
Sounds like something isn't working. Do you get a check engine light with the est wire off?
Last edited by 84 4+3; Jun 27, 2020 at 09:04 AM.
Drifting
Joined: Jun 2018
Posts: 1,402
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From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
Did you turn it off and on? There is a bit of advance in the module, but you have to turn it off and back on for the ECM to take control. Then the car will idle at something around 20 deg instead of 6deg.
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Thread Starter
Drifting
Joined: Feb 2013
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What we did was follow the timing procedure. IDI am going from memory sotso if it is not correct forgive me. Disconnected the IAC, turned on the car, waited 45 seconds. Start the car check/set the timing. Plug in EST. The timing stayed at 6 deg. My mechanic said it should have advanced to 19 deg. Then we throttled the car and the timing still didn't advance.
we are going to check the wires to the module.
Thank you for the help
we are going to check the wires to the module.
Thank you for the help
Drifting
Joined: Jun 2018
Posts: 1,402
Likes: 287
From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
What we did was follow the timing procedure. IDI am going from memory sotso if it is not correct forgive me. Disconnected the IAC, turned on the car, waited 45 seconds. Start the car check/set the timing. Plug in EST. The timing stayed at 6 deg. My mechanic said it should have advanced to 19 deg. Then we throttled the car and the timing still didn't advance.
we are going to check the wires to the module.
Thank you for the help
we are going to check the wires to the module.
Thank you for the help
after you plug the est back in you NEED to turn the engine off and on before the ECM will manage the timing. What part of this don’t you understand?
Thread Starter
Drifting
Joined: Feb 2013
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Sir, that is so rude. Like I said I was trying to tell you we followed the FSM procedure. But, I am recalling what we did. I believe we had to jumper A and B on the ALDL. And wait 45 seconds so the ECM would go into diagnostic mode.
have a good night.
have a good night.
Drifting
Joined: Jun 2018
Posts: 1,402
Likes: 287
From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
I sorry you think it’s rude but I’ve said it three times now and you seam to be missing the point. A jumper between A and B is irrelevant with regard to setting the timing. So x4 after you reconnect the EST the ECM will not manage the timing until you switch the ignition off and then restart the car.
Thread Starter
Drifting
Joined: Feb 2013
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I sorry you think it’s rude but I’ve said it three times now and you seam to be missing the point. A jumper between A and B is irrelevant with regard to setting the timing. I am not missing the point and I appreciate your frustration. The point I was making. Is that if what you are telling me to do is the FSM procedure we did it.
So x4 after you reconnect the EST the ECM will not manage the timing until you switch the ignition off and then restart the car. The next time I am at the car I am going to heed what you are saying. Interestingly enough. The car idled very good yesterday. So I am thinking that being the car was off and now is restarted the ECM is now managing the timing. AS you stated it would.
So let me ask you.
I go to the car. Start it. connect a timing light. The EST is connected.
The timing mark is at 6 or is it advanced?
I throttle the car.
The timing should advance correct.
Thank you for staying with me on this
So x4 after you reconnect the EST the ECM will not manage the timing until you switch the ignition off and then restart the car. The next time I am at the car I am going to heed what you are saying. Interestingly enough. The car idled very good yesterday. So I am thinking that being the car was off and now is restarted the ECM is now managing the timing. AS you stated it would.
So let me ask you.
I go to the car. Start it. connect a timing light. The EST is connected.
The timing mark is at 6 or is it advanced?
I throttle the car.
The timing should advance correct.
Thank you for staying with me on this
Safety Car
Joined: Sep 2004
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From: Mission Viejo CA
I'm not trying to be rude, but I think you owe Greg an apology.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,460
Likes: 48
You started off good, but then the conversation got confusing. You said you went from memory of the FSM procedure, but your description sure didn't follow the FSM! On what page of the FSM describes your procedure? Do you have a genuine FSM, or one of the generic Corvette books?
Good questions and thank you for the help. My mechanic looked up the timing setting procedure for the 85 Corvette.
I did not see the page.
We had to jumper A and B on the ALDL and wait 45 seconds. I thought that was to put the ECM in diagnostic mode, I may be wrong.
We set the timing with the EST disconnected and then reconnected the EST. According to Greg. I think we should have shut the car. And on the restart the ECM would set the timing. And like I said I think that is what happened because on the next day my mechanic started the car and it was idling better. So I think. That what Greg said is what occurred.
I never realized that the car had to be restarted in order for the setting to be registered by the ECM. Frankly I do not think that the procedure said that.
I'm not trying to be rude, but I think you owe Greg an apology.
With respect to my conversation with Greg. I was not ignoring him. Which is what he thought I was doing. The car is not with me. It is in a shop that is locked up. I do not have access until Monday here. I appreciate all of the help you guys offer. I truly do. And, I do not ignore you.
Now that the ECM is most probably controlling the timing, being the car has been on and off.
If I turn on the car with the EST connected.
Where will the timing be 6 deg or 19/20 deg.
If I throttle the car above 1500 rpm.
The timing will advance, correct.
Thank you
So please let me ask again.
Good questions and thank you for the help. My mechanic looked up the timing setting procedure for the 85 Corvette.
I did not see the page.
We had to jumper A and B on the ALDL and wait 45 seconds. I thought that was to put the ECM in diagnostic mode, I may be wrong.
We set the timing with the EST disconnected and then reconnected the EST. According to Greg. I think we should have shut the car. And on the restart the ECM would set the timing. And like I said I think that is what happened because on the next day my mechanic started the car and it was idling better. So I think. That what Greg said is what occurred.
I never realized that the car had to be restarted in order for the setting to be registered by the ECM. Frankly I do not think that the procedure said that.
I'm not trying to be rude, but I think you owe Greg an apology.
With respect to my conversation with Greg. I was not ignoring him. Which is what he thought I was doing. The car is not with me. It is in a shop that is locked up. I do not have access until Monday here. I appreciate all of the help you guys offer. I truly do. And, I do not ignore you.
Now that the ECM is most probably controlling the timing, being the car has been on and off.
If I turn on the car with the EST connected.
Where will the timing be 6 deg or 19/20 deg.
If I throttle the car above 1500 rpm.
The timing will advance, correct.
Thank you
So please let me ask again.
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,460
Likes: 48
Greg,
I really do appreciate the help you guys give me. I felt you thought that I was ignoring you. I was not. If I were going to ignore people I would not ask for their advice and help. Sorry for the confusion.
I really do appreciate the help you guys give me. I felt you thought that I was ignoring you. I was not. If I were going to ignore people I would not ask for their advice and help. Sorry for the confusion.
Drifting
Joined: Jun 2018
Posts: 1,402
Likes: 287
From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
Yep that’s correct if you start it now the timing should be controlled by the ECM and idle somewhere around 20 deg (I cant remember exactly) and yes it will advance as you rev it. With regard to the other things, I’m only trying to help and sometimes tone doesn’t convey correctly in written text. I appreciate your response, don’t sweat it and hopefully when you put a timing light on the car next time the results will be as expected, if not we can work the next problem.
Drifting
Joined: Jun 2018
Posts: 1,402
Likes: 287
From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
it’s all good mate I really didn’t mean to be rude but I can certainly see how It came across that way. These cars really are quite straightforward particularly with a FSM. There are plenty of people Here who will offer help willingly when things become ambitious.