Guitared
Member
I would appreciate any help. "The Bullet" has been sitting in my garage all summer. Withdrawal symptoms have become unbearable. I need a fix for me and my Vette.
I've been troubleshooting my LT4 for over two months, off and on. The problem is the fuel mixture is far too rich. It smokes and smells of gas and runs terrible. The only way to start it is to push accelerator pedal to almost WOT. The only DTC code is P0300 (random misfire - I knew that). It runs too rich at initial starting (open loop) and after it has warmed up (closed loop). I've clean and tested the fuel injectors. I'm confident they are working properly. I've replaced the fuel pump, ignition coil and spark plugs. The spark plugs, all 8, were heavy carbon fouled but not wet. The fuel pressure is OK at about 45 PSI.
I measured the injector pulse width using a current probe and oscilloscope at idle, open loop. The PW is approximately 10mS on all eight cylinders. I measured from the beginning of current flow to the termination of current flow. The actual time the injector was delivering fuel is about 1.0mS less considering the time needed to open the injector. I can see this as a bump on the current waveform. Researching online, it appears the PW should be on the order of 2.5 to 3.5 mS at idle. Having said that I know this value is for ordinary cars, not necessarily for LT4s.
I have two questions:
1) Does anyone know what I should expect for the PW at idle?
2) Assuming the PW is spot on and I move my troubleshooting effort to ignition, is there an easy way to determine if adequate spark is being delivered. Looking at the effort and cost of replacing the Opti-spark, I'm hoping I can troubleshoot it without just replacing it.
Thanks in advance for your help. Also, if it turns out the PW is too wide, where would I look for the trouble that would affect closed and open loop control?
I've been troubleshooting my LT4 for over two months, off and on. The problem is the fuel mixture is far too rich. It smokes and smells of gas and runs terrible. The only way to start it is to push accelerator pedal to almost WOT. The only DTC code is P0300 (random misfire - I knew that). It runs too rich at initial starting (open loop) and after it has warmed up (closed loop). I've clean and tested the fuel injectors. I'm confident they are working properly. I've replaced the fuel pump, ignition coil and spark plugs. The spark plugs, all 8, were heavy carbon fouled but not wet. The fuel pressure is OK at about 45 PSI.
I measured the injector pulse width using a current probe and oscilloscope at idle, open loop. The PW is approximately 10mS on all eight cylinders. I measured from the beginning of current flow to the termination of current flow. The actual time the injector was delivering fuel is about 1.0mS less considering the time needed to open the injector. I can see this as a bump on the current waveform. Researching online, it appears the PW should be on the order of 2.5 to 3.5 mS at idle. Having said that I know this value is for ordinary cars, not necessarily for LT4s.
I have two questions:
1) Does anyone know what I should expect for the PW at idle?
2) Assuming the PW is spot on and I move my troubleshooting effort to ignition, is there an easy way to determine if adequate spark is being delivered. Looking at the effort and cost of replacing the Opti-spark, I'm hoping I can troubleshoot it without just replacing it.
Thanks in advance for your help. Also, if it turns out the PW is too wide, where would I look for the trouble that would affect closed and open loop control?