What could cause random multiple misfire code?
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From: on the dyno tuning in MD
What could cause random multiple misfire code? Out doing a little test and tune. Had it at WOT watching O2s on live data - they were at .905 and no KR. All of a sudden, after hitting 3rd gear, the car just falls on its face and the SES light starts flashing. The car runs fine after I get out of the throttle, no misses or anything. I stop and pull the code and it is random multiple misfire code (didn't write down the number).
I clear the code and it runs fine. No misses or stummbles - nothing! Any idea?
It is an A4. My rev limiter is 300rpm above my shift point, and I did not hit it. Shift point 6,200rpm, rev limiter 6,500rpm.
Any ideas? Thanks in advance!
I clear the code and it runs fine. No misses or stummbles - nothing! Any idea?
It is an A4. My rev limiter is 300rpm above my shift point, and I did not hit it. Shift point 6,200rpm, rev limiter 6,500rpm.
Any ideas? Thanks in advance!
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From: Cal
Re: What could cause random multiple misfire code? P0300.
You might want to check your plugs, especially if they're platinum. Take out a few and compare them to each other or to a new one. Hope that helps.
You might want to check your plugs, especially if they're platinum. Take out a few and compare them to each other or to a new one. Hope that helps.
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From: on the dyno tuning in MD
Re: What could cause random multiple misfire code? I have NGK TR-55 plugs. They only have 1,500 miles on them. I'll pull some and check. The weird thing is that it doesn't have any miss or stumble to it - other than the slight lope of the LS6 cam. It seems to run so good.
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From: Raleigh, NC
Re: What could cause random multiple misfire code? I agree the plugs are suspect.
For instance, if they were fouled for some reason, you could run like ***** to the wall up to around 5000 or so RPM and then it would fall flat on it's face. The random misfires point that way, too. Check 'em!
For instance, if they were fouled for some reason, you could run like ***** to the wall up to around 5000 or so RPM and then it would fall flat on it's face. The random misfires point that way, too. Check 'em!
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From: on the dyno tuning in MD
Re: What could cause random multiple misfire code? I pulled several out - they all looked good.
Something else - I read on another old post that misfires can come in from trans or torque convertor slippage. Is this true? I had lowered my line pressure to see how it would shift before this run (it was killin some tires before) - I guess I lowered it too much because it was very sluggish - I actually thought something went in the trans for a second.
I checked all DTCs (even the ones that don't throw a light) and there was one in there about trans component slippage.
Could that be it? I put the shift pressure back up.
I'm wondering if the stock A4 is gonna hold up long behind this LS6! I hope so, I can't afford any more for a while!
Something else - I read on another old post that misfires can come in from trans or torque convertor slippage. Is this true? I had lowered my line pressure to see how it would shift before this run (it was killin some tires before) - I guess I lowered it too much because it was very sluggish - I actually thought something went in the trans for a second.
I checked all DTCs (even the ones that don't throw a light) and there was one in there about trans component slippage.
Could that be it? I put the shift pressure back up.
I'm wondering if the stock A4 is gonna hold up long behind this LS6! I hope so, I can't afford any more for a while!
Re: What could cause random multiple misfire code? ok here is what you can do... on atap log the current misfire history for all the plugs 1-8... that will show misfires in real time as you get them. Then we can narrow it down to what and where its coming from. Are all your plug wires fine also? But log those and see if its coming from a certain cylinder maybe
you wont get misfires from trans slippage that i know of. Enough misfires will cause the trans to lock and unlock outta no where though..
let me know how it looks under current history cruising and at WOT
you wont get misfires from trans slippage that i know of. Enough misfires will cause the trans to lock and unlock outta no where though..
let me know how it looks under current history cruising and at WOT
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From: on the dyno tuning in MD
Re: What could cause random multiple misfire code? The thing is, I don't have A-Tap. I only have live data on the Predator and DTCs on the Predator. 
The plug wires are fine as far as I can tell. I don't think it is something like that, because it is running too good. Could it have been some hiccup by chance?
I think I will just take it easy on it and see how it looks on the dyno and wideband - I don't trust the O2s and live data very much. Hopefully it won't come in while I am making a pull.
The plug wires are fine as far as I can tell. I don't think it is something like that, because it is running too good. Could it have been some hiccup by chance?
I think I will just take it easy on it and see how it looks on the dyno and wideband - I don't trust the O2s and live data very much. Hopefully it won't come in while I am making a pull.
