dwdooley
Full Member
2005 5.3 flex fuel Custom Avalanche with 150,00 miles will not idle smooth below 900 rpm.
Magnuson Supercharger, Dynatec long tube headers, Corsa Sport tube exhaust with high flow cats. (New Cats are about 2 years old.)
I clear codes and once it idles down and starts idling rough at 500 to 600 it then triggers Lean bank 1, and lean bank 2, plus multiple misfires.
Since this has an aluminum intake, shouldn't have itake gasket leak but I have sprayed Carb cleaner around intake for leaks but fuel trims stayed constant with no idle change.
Process of elimination listed below, all done in last two weeks. I have done all this my self and I'm 66. Getting to old for this stuff.
1. New flex fuel A.C. Delco fuel pump and New Evap Canister = Now have a solid 60 PSI at fuel rail.
2. New coil packs, Plug wires are new, and installed new Autolite Iridium XP plugs gaped at .040" (The NGK TR6's pulled out were clean and light brown).
3. New AiRaid Filter .... old one was just old.
4. New intake bellows after MAF .... found a tear in it.
After start up it ran smoother for about 20 miles but not perfectly smooth, then it slowly got worse and back to same condition as before.
I then used my scanner and continued to find my STFT adding 30% to fuel curve ..... BUT HERE IS WHERE I'M STUMPED ...
When I disconnect the MAF it slowly idles down to 700 and runs Great! ,,,,,, Sooooo
5. I Overnighted a Delpi MAF and just installed it .....WOW ..... still does the same thing!
6. Cleaned throttle body with carb cleaner too
I NEED some Knowledge here PLEASE?
What is weird is that when I disconnect the MAF my engine runs great and actually accelerates hard and steady. Only issue w MAF unplugged is that when you let off the gas it takes about 3 seconds to drop down to 700 rpm from around 1300 rpm.
In closed loop and on the O2's it is 1.1=.6 2.1=.7 1.2=.3 2.2=.0
I am not real good at reading 02's
Here's the kicker .... when I unplug the MAF .... STFT drops to 0 ... toggles + & - like it should ... and LTFT also within 2%
I have replace all vacuum plugs on throttle body and intake. and my PCV valves are piped to a oil purge atmospheric tank.
I am thinking about having it smoked tomorrow for any possible vacuum leaks that I might not see, but why wouldn't that show up with MAF disconnected and in closed loop show something on the 02's??
WHAT AM I MISSING??
ANY HELP HERE WOULD BE APPRECIATED
Magnuson Supercharger, Dynatec long tube headers, Corsa Sport tube exhaust with high flow cats. (New Cats are about 2 years old.)
I clear codes and once it idles down and starts idling rough at 500 to 600 it then triggers Lean bank 1, and lean bank 2, plus multiple misfires.
Since this has an aluminum intake, shouldn't have itake gasket leak but I have sprayed Carb cleaner around intake for leaks but fuel trims stayed constant with no idle change.
Process of elimination listed below, all done in last two weeks. I have done all this my self and I'm 66. Getting to old for this stuff.
1. New flex fuel A.C. Delco fuel pump and New Evap Canister = Now have a solid 60 PSI at fuel rail.
2. New coil packs, Plug wires are new, and installed new Autolite Iridium XP plugs gaped at .040" (The NGK TR6's pulled out were clean and light brown).
3. New AiRaid Filter .... old one was just old.
4. New intake bellows after MAF .... found a tear in it.
After start up it ran smoother for about 20 miles but not perfectly smooth, then it slowly got worse and back to same condition as before.
I then used my scanner and continued to find my STFT adding 30% to fuel curve ..... BUT HERE IS WHERE I'M STUMPED ...
When I disconnect the MAF it slowly idles down to 700 and runs Great! ,,,,,, Sooooo
5. I Overnighted a Delpi MAF and just installed it .....WOW ..... still does the same thing!
6. Cleaned throttle body with carb cleaner too
I NEED some Knowledge here PLEASE?
What is weird is that when I disconnect the MAF my engine runs great and actually accelerates hard and steady. Only issue w MAF unplugged is that when you let off the gas it takes about 3 seconds to drop down to 700 rpm from around 1300 rpm.
In closed loop and on the O2's it is 1.1=.6 2.1=.7 1.2=.3 2.2=.0
I am not real good at reading 02's
Here's the kicker .... when I unplug the MAF .... STFT drops to 0 ... toggles + & - like it should ... and LTFT also within 2%
I have replace all vacuum plugs on throttle body and intake. and my PCV valves are piped to a oil purge atmospheric tank.
I am thinking about having it smoked tomorrow for any possible vacuum leaks that I might not see, but why wouldn't that show up with MAF disconnected and in closed loop show something on the 02's??
WHAT AM I MISSING??
ANY HELP HERE WOULD BE APPRECIATED