no spark advance...why!?
Thread Starter
Melting Slicks
Joined: Jan 2008
Posts: 2,065
Likes: 1
From: Jasper Texas
no spark advance...why!?
For the longest time...I have been fighting a rough idle/rich condition...and I think I just found why.
I have NO spark advance...ever. This would definitely cause a rich condition, popping out of the exhaust while cruising/decelerating, and a rough idle.
So...where should i look to figure this one out? esc module is new, est is plugged in. The only thing I've done to the system is the knock sensor bypass.
I bet this car is fun up top when I actually get proper spark back!
I have NO spark advance...ever. This would definitely cause a rich condition, popping out of the exhaust while cruising/decelerating, and a rough idle.
So...where should i look to figure this one out? esc module is new, est is plugged in. The only thing I've done to the system is the knock sensor bypass.
I bet this car is fun up top when I actually get proper spark back!
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For the longest time...I have been fighting a rough idle/rich condition...and I think I just found why.
I have NO spark advance...ever. This would definitely cause a rich condition, popping out of the exhaust while cruising/decelerating, and a rough idle.
So...where should i look to figure this one out? esc module is new, est is plugged in. The only thing I've done to the system is the knock sensor bypass.
Knock system controls timing right? Maybe recheck bypass situation. Not sure here, but isnt timing controlled by ECM?
I bet this car is fun up top when I actually get proper spark back!
I have NO spark advance...ever. This would definitely cause a rich condition, popping out of the exhaust while cruising/decelerating, and a rough idle.
So...where should i look to figure this one out? esc module is new, est is plugged in. The only thing I've done to the system is the knock sensor bypass.
Knock system controls timing right? Maybe recheck bypass situation. Not sure here, but isnt timing controlled by ECM?
I bet this car is fun up top when I actually get proper spark back!
Good Luck. I understand your pain. Drives me batty when the vette isnt running correctly.
Corvette Mike
Le Mans Master
Joined: Aug 2000
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From: Australia
We discussed this with you in the past.
The ECM needs to "see" the KC. If it doesn't, it probably assumes the KC is not working and defaults to a
low / no SA to prevent you blowing up engine.
How about hooking the KC back up and see if your SA comes back?
Melting Slicks
Joined: Aug 2003
Posts: 3,401
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From: Lakeville MI
Can you elaborate on what you mean by "no spark advance"?
Does this mean 0 degrees at all times, 6 degrees or base timing at all times or 20 degrees advance relative to tdc at all times. Please clarify if you can.
I assume that when monitoring with a scan tool that you're seeing a fixed spark advance of 20 degrees relative to tdc.
Does this mean 0 degrees at all times, 6 degrees or base timing at all times or 20 degrees advance relative to tdc at all times. Please clarify if you can.
I assume that when monitoring with a scan tool that you're seeing a fixed spark advance of 20 degrees relative to tdc.
Thread Starter
Melting Slicks
Joined: Jan 2008
Posts: 2,065
Likes: 1
From: Jasper Texas
knock sensor bypass was done by putting a toggle switch in the ground of the esc module. I removed and it made no difference. Only code is a 44....I need a heated o2. :o
tequilaboy:
On the scan tool, it shows spark advance: 0 at all times. base timing is set at 10 btdc.
One thing I'm unsure of though: could the scan tool cause a "fixed" spard advance, like when jumping the a&b ports and running?
tequilaboy:
On the scan tool, it shows spark advance: 0 at all times. base timing is set at 10 btdc.
One thing I'm unsure of though: could the scan tool cause a "fixed" spard advance, like when jumping the a&b ports and running?
Thread Starter
Melting Slicks
Joined: Jan 2008
Posts: 2,065
Likes: 1
From: Jasper Texas
bump
does the icm control the spark advance? Or is it the prom?
does plugging in a scan tool to an '85 create fixed spark advance? car seemed to run the same with the scanner plugged in, so I'd assume not....need help here, kind of a serious issue.
does the icm control the spark advance? Or is it the prom?
does plugging in a scan tool to an '85 create fixed spark advance? car seemed to run the same with the scanner plugged in, so I'd assume not....need help here, kind of a serious issue.
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knock sensor
I dont understand the what advantage is of not having a knock sensor. Doesnt it make ajustments in timing as you drive depending on conditions? 
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scanner
IMO... a scanner is a read of whats happening. IMO........it doesnt change settings. I may be wrong.... JMO..
Why do you need a heated o2? Your car did not come with one.
Why do you need a heated o2? Your car did not come with one.
Le Mans Master
Joined: Aug 2000
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From: Australia
Because when you install headers with the O2 in the collector, the stock sensor cools off below it's operating temp at idle and drops out of operation; puts the engine back into open loop at idle.
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Rod
I stand corrected. Thank you. I learned something tonight
Thread Starter
Melting Slicks
Joined: Jan 2008
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From: Jasper Texas
Now...knowing that...could the scanner be the reason I see that? I mean...should I be able to spin through first and second (auto) and pull right up to 7K rpms with no spark advance?
Team Owner
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From: Summerland B.C. Canada
Instructor
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so if my Check engine light is on for a knock sensor, it is pulling timing automatically? i have a bad knock sensor that i plan to swap out... is this killing my power?
Last edited by cgm12mgc; Jan 10, 2009 at 02:27 AM.
Le Mans Master
Joined: Aug 2000
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From: Australia
The ECM checks the circuit.If it finds a fault it throws a code.
The fault could be the sensor, (in your case the KC) , or it could be a bad earth , loose connector, etc.
From memory if the KC circuit is in fault the ECM defaults to a low / no spark advance setting to prevent you blowing up your engine.
Le Mans Master
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From: Hellinois
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Hi Cord, my '85 is up on stands for the winter but I will be firing it sometime in the next few days to get it limbered up a bit. I can't remember if my cheap scanner will show timing but I will hook it up and see what it reads for you. I'll keep an eye here in case you get an answer. I'm a bit busy now or I would do it sooner.
Le Mans Master
Joined: May 2004
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From: Hellinois
Finalist 2020 C4 of the Year - Modified
Cord, I apologize, I kept you waiting for nothing. My Autoxray 2000 does not read timing. I even bought the extra program to allow scanning of OBD1 on it. This is what I get for trying to save $$$. At least this will get the thread back on top and maybe someone can give you an answer. Now I think I will go to THAT auction site and see if I can find a good unit.