Timing and idle diagnosis + help
08-15-16, 11:41 AM
#1
Rotary Freak
Thread Starter
Timing and idle diagnosis + help
I've recently acquired a 1986 NA Rx7.
After fixing an issue where my cold start system did not function, I noticed the idle was high (around 1300 RPM) and a little bit lumpy. After adjusting it down, my father adjusted the timing as well using a timing light. We noticed that the Crank sensor (CAS, is it?) is adjusted all the way to one side using the 10mm nut, and the car seems to be a little bit sluggish now. It no longer has the power that it had before we adjusted it. Sometimes it will stall when we are driving and we come to a stop, or idle down to 400 before recovering. The temperature seems a little higher than it was before, but it is also a very hot day here.
I have read a few threads and articles about timing adjustment and idle adjustment, and I don't really understand the process. What I would like to do is verify that the crank sensor is installed correctly, verify the idle is correct (750, I believe), and then adjust for accurate timing. Could anyone give me a very brief write up about how to properly do this? I am not understanding based on the manual or the Haynes manual.
Also, I am curious about the consequences of incorrect timing. If the timing is significantly retarded or advanced, what is the result? Can it be harmful to the engine?
Thank you.
After fixing an issue where my cold start system did not function, I noticed the idle was high (around 1300 RPM) and a little bit lumpy. After adjusting it down, my father adjusted the timing as well using a timing light. We noticed that the Crank sensor (CAS, is it?) is adjusted all the way to one side using the 10mm nut, and the car seems to be a little bit sluggish now. It no longer has the power that it had before we adjusted it. Sometimes it will stall when we are driving and we come to a stop, or idle down to 400 before recovering. The temperature seems a little higher than it was before, but it is also a very hot day here.
I have read a few threads and articles about timing adjustment and idle adjustment, and I don't really understand the process. What I would like to do is verify that the crank sensor is installed correctly, verify the idle is correct (750, I believe), and then adjust for accurate timing. Could anyone give me a very brief write up about how to properly do this? I am not understanding based on the manual or the Haynes manual.
Also, I am curious about the consequences of incorrect timing. If the timing is significantly retarded or advanced, what is the result? Can it be harmful to the engine?
Thank you.
08-17-16, 10:17 AM
#2
Go here and get the service manual for your car and see what the idle specs and timing should be at.
Foxed.ca - Mazda RX-7 Manuals
As for high advance and retarded timing, having high advance timing can be really bad. You are igniting before the peak of the compression. This can cause knock and even worse detonation. (Super bad on Turbo cars, can blow a hole in your engine...)
As for retarded timing, you are igniting after peak compression which you will have sluggish response, loss of power etc. But you wont have anything as bad detonation.
You want to be on TDC (Top Dead Center) for your timing if possible.
Foxed.ca - Mazda RX-7 Manuals
As for high advance and retarded timing, having high advance timing can be really bad. You are igniting before the peak of the compression. This can cause knock and even worse detonation. (Super bad on Turbo cars, can blow a hole in your engine...)
As for retarded timing, you are igniting after peak compression which you will have sluggish response, loss of power etc. But you wont have anything as bad detonation.
You want to be on TDC (Top Dead Center) for your timing if possible.
08-17-16, 08:35 PM
#3
Rotary Freak
Thread Starter
Okay, I've adjusted as far as I can (based on Haynes manual and an online write-up) and the car seems to be running okay with no more stumbling. Also installed new BURR7EQ's. To adjust timing, we removed the CAS, removed the top cover, made sure that everything was aligned, reinstalled, and made sure that it remained aligned. To adjust timing to the mark, we had to rotate the CAS counterclockwise. Should the lock nut be at the very far end of the adjustment limit? If it should not be at the end of the adjustment limit, what can we do to fix this?
08-18-16, 02:36 AM
#4
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If the Cas is stabbed correctly then as long as the Timing marks align on the crank when you set the final timing by moving the CAS it shouldn't really matter where the Cas was adjusted to.
If the marks align correctly on the pulley,moving the Cas just "fine tunes it more" and then you just lock the nut down" and Bob's Your Uncle!
By the way the Leading plugs are BUR7EQ's..the Trailing plugs are BUR9EQ's
If the marks align correctly on the pulley,moving the Cas just "fine tunes it more" and then you just lock the nut down" and Bob's Your Uncle!
By the way the Leading plugs are BUR7EQ's..the Trailing plugs are BUR9EQ's
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