leading and trailing coils firing at same time???
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Senior Member
Joined: Sep 2004
Posts: 251
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From: las vegas
leading and trailing coils firing at same time???
as the topic says, for some reason my leading and trailing coils are firing at the same time. a brand new streetported motor in my car( 950 miles ), i recently had some problems where i had to take the front cover off of the motor and put in back on. so i had to reset the timing which is perfect on the the first timing mark, 5 degrees past top dead, and i went to check the trailing plugs and they are firing at the same time as the leading plugs. im stumped ive never seen this happen before. if any of you have any advice it would be greatly appreciated.
HAILERS
Joined: May 2001
Posts: 20,563
Likes: 27
From: FORT WORTH, TEXAS,USA
LEAD at idle is minus 5
TRAIL at idle is minus 20
Engine speed has a lot to do with timing. Once over 1100-1200 rpm, the timing advances automatically by the ECU.
Attached are two jps of a graph of the timing. One shows timing at idle, The other shows timing just above the 1100-1200 rpm mark.
Notive how at idle the timing is -5 and -20.
Notice again how when over 1100 rpm, the timing is for BOTH the Lead and Trail at almost the same figure? I do. Something like both at PLUS 12.6 degrees.
So I'm saying, if the engine is not below 1100 rpm, the ECU advances the timing and they will both, lead and trail, be close to the same figure.
So here you are, over 1100 rpm turning the CAS so the LEAD mark will hit the five degree hash mark. Then you put the timing light on the trail and wonder why it also shows up at the SAME five degree mark. You shouldn't wonder anymore after looking at the two graphs attached.
If your rpms were for sure below the 1100 rpm, say closer to 750 rpm, and the lead and trail were on the same mark..........I've not a clue why.
TRAIL at idle is minus 20
Engine speed has a lot to do with timing. Once over 1100-1200 rpm, the timing advances automatically by the ECU.
Attached are two jps of a graph of the timing. One shows timing at idle, The other shows timing just above the 1100-1200 rpm mark.
Notive how at idle the timing is -5 and -20.
Notice again how when over 1100 rpm, the timing is for BOTH the Lead and Trail at almost the same figure? I do. Something like both at PLUS 12.6 degrees.
So I'm saying, if the engine is not below 1100 rpm, the ECU advances the timing and they will both, lead and trail, be close to the same figure.
So here you are, over 1100 rpm turning the CAS so the LEAD mark will hit the five degree hash mark. Then you put the timing light on the trail and wonder why it also shows up at the SAME five degree mark. You shouldn't wonder anymore after looking at the two graphs attached.
If your rpms were for sure below the 1100 rpm, say closer to 750 rpm, and the lead and trail were on the same mark..........I've not a clue why.
Thread Starter
Senior Member
Joined: Sep 2004
Posts: 251
Likes: 0
From: las vegas
ok that helps alot guys, thank you i tihnk the problem is that i was setting the timing with it idling over 1000 rpm, but when i bring it lower than 1000 it doesnt want to idle =( it just keeps wanting to die. im going to play with it today. thanks again guys
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