Code 55 Lean Condition at WOT

[XfireZ51]

Well took the car out again after having re-gap of plugs and raising Fuel Cutoff point. Still set a code at WOT. And I noticed that when I first "got on it', it just didn't feel like it had the grunt. I'm thinking fuel pump.

[-=Jeff=-]

I STILL say.. put the old plugs in and see if the problem is still there.. this way you KNOW for sure if you need a Fuel Pump.. this started AFTER the plug change. why not swap them back, should only take 20min to swap

[tpepmeie]

Originally Posted by XfireZ51

You'll find them starting at 614 and going thru 61D. If you could review the hack for the $D0A def, that would help. Here's another question to contemplate. Could it be that the code was written as to ignore the cause of the malf? So even if the ECM was the cause of the lean exhaust,
it would still set a code 55? Or if Fuel Cutoff, then ECM should ignore the Lean Exhaust?
My gut tells me GM would play it safe and not bypass the malf flag even tho it was a previous ECM action that caused the malf in the first place.

Dom, I finally checked my disassemblies. Those params are not quite what you have described. You've got Fuel Cut and Fuel Resume RPMs, and Speed limits. There are two separate RPM limits & resume values. One is invoked in "Converter Protection" mode.

Todd

[XfireZ51]

Originally Posted by tpepmeie

Dom, I finally checked my disassemblies. Those params are not quite what you have described. You've got Fuel Cut and Fuel Resume RPMs, and Speed limits. There are two separate RPM limits & resume values. One is invoked in "Converter Protection" mode.

Todd

Got it. Very much appreciated. I'll be working on fuel system components tomorrow. Least expensive first, Fuel Filter, then onto pumps.

[Tyler Townsley]

Originally Posted by -=Jeff=-

I STILL say.. put the old plugs in and see if the problem is still there.. this way you KNOW for sure if you need a Fuel Pump.. this started AFTER the plug change. why not swap them back, should only take 20min to swap

If the plugs are not resistor type they will get noisy and cause rfi problems. This happened several years ago with some of the plugs recommended for the LT 5. I have a set I never installed because of the problems others experienced so take the advice and go back to a set of plugs you know worked.

Tyler

[XfireZ51]

Originally Posted by Tyler Townsley

If the plugs are not resistor type they will get noisy and cause rfi problems. This happened several years ago with some of the plugs recommended for the LT 5. I have a set I never installed because of the problems others experienced so take the advice and go back to a set of plugs you know worked.

Tyler

Tyler,

Thanks. I read about that. However, the new plugs I installed are resistor.
The installation of new plugs and the Code 55 are purely coincidental.
Pulled the fuel pumps today and I think I know now what caused the Code55. I'll update with pics once I have car running tomorrow.

[XfireZ51]

On a hunch, I pulled the pumps and what I found wasn't a surprise. I'm guessing there was enough fuel flow for Part Throttle. Once you punched it, it would run until it exhausted the fuel in the lines and then the pump wasn't able to keep up. Now it feels as if it has secondaries even tho they're out. SOTP feels like its really starting to hustle.
Yeah, I replaced the pumps because that kind of restriction could damage them. They looked original equipment.