Strange shutdown that I can't explain...
10-09-2011, 01:40 PM
#1
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Strange shutdown that I can't explain... Ok guys,
I'm having a problem with a car that will backfire and shut down only under WOT.
It will rev up, backfire, then just slowly die. Nothing will bring it back, but the car will start right back up.
You can see in the posted log around frame 1700 where it dies.
The stft's skyrocket, but there is no change in o2 readings.
The car has had two different ECM's, every sensor has been changed. The crank reluctor has been checked, and the thrust is at .005". Also, a completely new harness has been installed on the car.
I don't know what else to look for.
The car is a big cam ls1 F-body. Cam is a solid roller. I don't recall all the other mods. Also, the motor has been built, and the backfire thing has plagued the car for quite some time. I'm just the next in line to try and fix it, I guess.
Also, I don't have the car in the shop, so I'll need a plan of action of what to check when the car returns.
Also, I find it strange that the MAF will still read after it dies.
Any ideas?
I'm having a problem with a car that will backfire and shut down only under WOT.
It will rev up, backfire, then just slowly die. Nothing will bring it back, but the car will start right back up.
You can see in the posted log around frame 1700 where it dies.
The stft's skyrocket, but there is no change in o2 readings.
The car has had two different ECM's, every sensor has been changed. The crank reluctor has been checked, and the thrust is at .005". Also, a completely new harness has been installed on the car.
I don't know what else to look for.
The car is a big cam ls1 F-body. Cam is a solid roller. I don't recall all the other mods. Also, the motor has been built, and the backfire thing has plagued the car for quite some time. I'm just the next in line to try and fix it, I guess.
Also, I don't have the car in the shop, so I'll need a plan of action of what to check when the car returns.
Also, I find it strange that the MAF will still read after it dies.
Any ideas?
10-23-2011, 09:47 AM
#3
Post the tune.
You're not logging your IAC, so you can't tell anything thats going on as far as decel dashpot, etc.
LTFTs should be turned off with a big cam.
It looks like it runs out of fuel, or goes into DFCO and doesn't come back out. At least that's what the NB sensors look like. Would be nice to see what a WB says.
Depending on the size of the cam, I would recommend setting up in SD and possibly even open loop. Chances are the tune is just not right for the cam.
You're not logging your IAC, so you can't tell anything thats going on as far as decel dashpot, etc.
LTFTs should be turned off with a big cam.
It looks like it runs out of fuel, or goes into DFCO and doesn't come back out. At least that's what the NB sensors look like. Would be nice to see what a WB says.
Depending on the size of the cam, I would recommend setting up in SD and possibly even open loop. Chances are the tune is just not right for the cam.
Last edited by edcmat-l1; 10-23-2011 at 09:55 AM.
10-24-2011, 07:01 PM
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I never thought of the DFCO.
I know the car is not running out of fuel. It's plenty rich on the dyno.
But it will die while on throttle, and just won't come back.
I don't have the specs on the cam. I've been told it is in the upper 250's to lower 260's at .050". It's a solid roller cam as well.
Not my choice, but what was brought to me.
So, I also need to disable LTFT's... Kind of crappy. I like to leave those on whenever possible.
I know the car is not running out of fuel. It's plenty rich on the dyno.
But it will die while on throttle, and just won't come back.
I don't have the specs on the cam. I've been told it is in the upper 250's to lower 260's at .050". It's a solid roller cam as well.
Not my choice, but what was brought to me.
So, I also need to disable LTFT's... Kind of crappy. I like to leave those on whenever possible.