08 Tahoe ltz afm or fuel issues??!?

[Obiwanjacobi]

hello I picked up my Tahoe awhile back and had all kinds of issues. Replaced the ecm and wiring harness now all is well except when it switches from v8 to v4 mode it shakes and misfires pretty bad until the check engine comes on and flashes. The check engine will turn off after 15-30 seconds and it will just stay in v8 mode and seems to be fine. I still am getting a random misfire code along with codes p0171,p069e(fuel pump control module),p1175. It has also been stalling a lot lately but will always fire right back up. It seems like it mainly does it when coasting or slowing down and when it’s surging between v8 and v4 mode until it just stays in v8 mode then it won’t stall. I wish I could just disable it somehow but every time I restart it the process repeats until the check engine is tripped. Can this be a fuel pump issue or is it the afm manifold that’s bad? I am at a loss here and have already spent a bunch of $$$ trying to get this thing perfect it’s a great vehicle just is super annoying and frustrating that it keeps stalling and misfiring...

 

[swathdiver]

hello I picked up my Tahoe awhile back and had all kinds of issues. Replaced the ecm and wiring harness now all is well except when it switches from v8 to v4 mode it shakes and misfires pretty bad until the check engine comes on and flashes. The check engine will turn off after 15-30 seconds and it will just stay in v8 mode and seems to be fine. I still am getting a random misfire code along with codes p0171,p069e(fuel pump control module),p1175. It has also been stalling a lot lately but will always fire right back up. It seems like it mainly does it when coasting or slowing down and when it’s surging between v8 and v4 mode until it just stays in v8 mode then it won’t stall. I wish I could just disable it somehow but every time I restart it the process repeats until the check engine is tripped. Can this be a fuel pump issue or is it the afm manifold that’s bad? I am at a loss here and have already spent a bunch of $$$ trying to get this thing perfect it’s a great vehicle just is super annoying and frustrating that it keeps stalling and misfiring...

@Miami-Dade Gary, can you move this to the right forum please?

Jake, you first want to check Bank2, the passenger side of the engine for a massive vacuum leak. This is usually the intake gasket but could also be part of the PCV if a hose to the valve cover is loose or broken. Then make sure your oxygen sensors are GM OE or ACDelco and that the cat on that side is not plugged. Should not be. Bank 1 is also lean.

You need a good scan tool that can run a misfire graph of your engine which will tell you which cylinder(s) are misfiring. If you're LTFTs are -25 or near that at idle, that's the sign of a big vacuum leak.

It's true, I think your VLOM is toast or it is not getting enough oil pressure to operate correctly. The little filter under the oil pressure sensor could be plugged and or you have the wrong oil in the motor, wrong or restrictive oil filter or a worn oil pump. How is your oil pressure? This is an iron block LY5 or LMG motor right?


In 2011 GM introduced a new valve cover (PCV system) that reduces oil consumption, an improved VLOM and new AFM lifters along other improvements to make AFM more reliable and enduring. The best thing you can do with it is to disable it in the tune, leave it turned off.

 

[Obiwanjacobi]

@Miami-Dade Gary, can you move this to the right forum please?

Jake, you first want to check Bank2, the passenger side of the engine for a massive vacuum leak. This is usually the intake gasket but could also be part of the PCV if a hose to the valve cover is loose or broken. Then make sure your oxygen sensors are GM OE or ACDelco and that the cat on that side is not plugged. Should not be. Bank 1 is also lean.

You need a good scan tool that can run a misfire graph of your engine which will tell you which cylinder(s) are misfiring. If you're LTFTs are -25 or near that at idle, that's the sign of a big vacuum leak.

It's true, I think your VLOM is toast or it is not getting enough oil pressure to operate correctly. The little filter under the oil pressure sensor could be plugged and or you have the wrong oil in the motor, wrong or restrictive oil filter or a worn oil pump. How is your oil pressure? This is an iron block LY5 or LMG motor right?


In 2011 GM introduced a new valve cover (PCV system) that reduces oil consumption, an improved VLOM and new AFM lifters along other improvements to make AFM more reliable and enduring. The best thing you can do with it is to disable it in the tune, leave it turned off.

My stft and ltft are good I just went through all those issues due to my o2 sensors not reading right on bank 2. I have a pretty good scan tool it’s for Gm I just can’t graph with it it just shows me numbers. My oil pressure is good or at least I think it’s good it’s in between the first mark and 40 at idle and it sits at about 40 while driving. I also don’t have any oil consumption issues. What is the correct oil weight and type? I will be doing the oil change this week. Also how can I tell if my cats are clogged? My scan tool says they are at 1200 degrees when the engine is hot.

 

[swathdiver]

My stft and ltft are good I just went through all those issues due to my o2 sensors not reading right on bank 2. I have a pretty good scan tool it’s for Gm I just can’t graph with it it just shows me numbers. My oil pressure is good or at least I think it’s good it’s in between the first mark and 40 at idle and it sits at about 40 while driving. I also don’t have any oil consumption issues. What is the correct oil weight and type? I will be doing the oil change this week. Also how can I tell if my cats are clogged? My scan tool says they are at 1200 degrees when the engine is hot.

5W30 and has to be Dexos 1. Mobil 1, Shell Rotella Gas Truck work well. The Mobil 1 oil filter are pretty restrictive and I lost oil pressure using them. Went with K&N.

Easiest way to check the cats is to watch the downstream O2 sensors, they should be fairly steady. Temps vary depending on speed and time at speed.

I would mist some water or spray propane around the intake gaskets while watching the fuel trims after checking for vacuum leaks of the air hose, throttle body and PCV system.

 

[Obiwanjacobi]

5W30 and has to be Dexos 1. Mobil 1, Shell Rotella Gas Truck work well. The Mobil 1 oil filter are pretty restrictive and I lost oil pressure using them. Went with K&N.

Easiest way to check the cats is to watch the downstream O2 sensors, they should be fairly steady. Temps vary depending on speed and time at speed.

I would mist some water or spray propane around the intake gaskets while watching the fuel trims after checking for vacuum leaks of the air hose, throttle body and PCV system.

I’ve sprayed the whole engine down with carb cleaner because I thought the intake manifold had a leak before but I didn’t find anything that way. There was a cracked and dry rotted hose and I’ve replaced that already. Can it come from the egr? I replaced the valve in the rear off the tank but it didn’t come with a new hardline so I just spliced it together. I sprayed there too in hopes I would find something but I didn’t hear any changes in rpms.

 

[swathdiver]

I’ve sprayed the whole engine down with carb cleaner because I thought the intake manifold had a leak before but I didn’t find anything that way. There was a cracked and dry rotted hose and I’ve replaced that already. Can it come from the egr? I replaced the valve in the rear off the tank but it didn’t come with a new hardline so I just spliced it together. I sprayed there too in hopes I would find something but I didn’t hear any changes in rpms.

I'm not familiar with the EGR system as mine does not have one. @iamdub

 

[BG1988]

hello I picked up my Tahoe awhile back and had all kinds of issues. Replaced the ecm and wiring harness now all is well except when it switches from v8 to v4 mode it shakes and misfires pretty bad until the check engine comes on and flashes. The check engine will turn off after 15-30 seconds and it will just stay in v8 mode and seems to be fine. I still am getting a random misfire code along with codes p0171,p069e(fuel pump control module),p1175. It has also been stalling a lot lately but will always fire right back up. It seems like it mainly does it when coasting or slowing down and when it’s surging between v8 and v4 mode until it just stays in v8 mode then it won’t stall. I wish I could just disable it somehow but every time I restart it the process repeats until the check engine is tripped. Can this be a fuel pump issue or is it the afm manifold that’s bad? I am at a loss here and have already spent a bunch of $$$ trying to get this thing perfect it’s a great vehicle just is super annoying and frustrating that it keeps stalling and misfiring...

fuel pump


p1175 A/F imbalance Bank2
P069E Fuel pump control module
p0171 Fuel system too lean


So you replace random expensive parts before even checking the fuel pump pressure?

intake gasket is bad or fuel pump

Check the honey cone and clean the MAF sensor USE the correct cleaners

also the MAF sensor wire loom is known to become worn out

make sure the MAP sensor is plugged in correct
make sure the air filter is sit correctly
resit the connections for the wires( MAP and MAF)
what brand of fuel?


if you have a live data scanner you could see what is going on easy it's like 40$ for one at walmart

 

[Doubeleive]

in the wrong section @yates ™
I don't think the 08 has a EGR

 

[yates ™]

in the wrong section @yates ™
I don't think the 08 has a EGR

@Obiwanjacobi what year is your truck so that we can move this to the correct section.

 

[Doubeleive]

@Obiwanjacobi what year is your truck so that we can move this to the correct section.

title say's 08