Rough Cold Start Tahoe 5.3L - PLEASE HELP!

[bigdjatom416]

Hey gang!!

Hoping you all can help. I have a 2009 Tahoe LTZ 5.3L and its having a cold start issue. In the morning when I first start the engine its really rough and sometimes takes a few tries to start. After a few minutes it warms up and seems to run perfectly. Its been throwing P0172 and P0175 System To Rich Banks 1 and 2 codes.

I have installed new air filter, Mass Air Flow Sensor and Vapour Canister Purge Valve. I also cleaned out the throttle body. Anyone have any idea what to look at next?? I'll post the freeze frame data from the scanner in case it helps.

Freeze Frame Data:

DTCFRZF P0175
FUELSYS1 CL
FUELSYS2 CL
LOAD_PCT(%) 17.6
ETC(F) 192
SHRTFT1(%) 5.5
LONGFT1(%) -30.5
SHRTFT2(%) 4.7
LONGFT2(%) -30.5
FRP(psi) 43.5
MAP(inHg) 13.2
RPM(/min) 962
VSS(mph) 16
SPARKADV 12
IAT(F) 86
MAF(lb/min) 0.985
TP(%) 17.6
RUNTM(sec) 157
EVAP_PCI(%) 0.0
FLI(%) 24.7
WARM_UPS 1
CLR_DST(mile) 4
EVAP_VP(Pa) 16369
BARO(inHg) 29.4
CATEMP11(f) 1124.60
CATEMP21(f) 1124.60
VPWR(v) 14.168
LOAD_ABS(%) 28
EQ_RAT 0.999
TP_R(%) 3.5
AAT(f) 73
TP_B(%). 18.0
AAP_D(%) 20.8
APP_E(%) 10.2
TAC_PCT(%) 5.1

 

[j91z28d1]

do you have alcohol content % anywhere in your scanner data?

do you run e85 at all?

 

[Fless]

See if you can change your reading standard to metric -- would like to see g/sec on the MAF.

Does it always idle that high with a nearly-warm engine?

 

[j91z28d1]

See if you can change your reading standard to metric -- would like to see g/sec on the MAF.

Does it always idle that high with a nearly-warm engine?

my converter says it's 7.4464747 g/s

how right that is I don't know

 

[Fless]

my converter says it's 7.4464747 g/s

how right that is I don't know

I think that's fairly accurate but I like to see the numbers without having to convert. Seems like the MAF may be reporting properly, with that high of an idle the engine's going to move a bit more air than the 5.3L displacement.

Good question about the alcohol content -- the virtual alcohol sensor in these can go wacky and might need 1) a reset for now and 2) an updated calibration. Might also need to reset those LTFTs.

 

[j91z28d1]

I don't know what his scanner shows for throttle% at idle, like mine shows different depending on the scanner. my daily shows 19.93% throttle closed but his might now not, giving he's doing 16mph at this freeze frame. he might be driving.

-30 long term is crazy thou. something isn't happy

 

[strutaeng]

Yeah, maybe just an alcohol content reset? Seems kinda like a common thing on this generation, no?

Fuel pressure seems kinda in the ballpark, so I wouldn't that would be causing the issue.

 

[Fless]

I don't know what his scanner shows for throttle% at idle, like mine shows different depending on the scanner. my daily shows 19.93% throttle closed but his might now not, giving he's doing 16mph at this freeze frame. he might be driving.

-30 long term is crazy thou. something isn't happy

Yeah, I missed the speed PID. Thought it was idling in Park.

 

[strutaeng]

Ya. @Fless was hinting that OP should post live data PID (MAF) at idle. To see if MAF reporting jives...

Hopefully OP have live data stream. Looks like the CEL got triggered like at 17 mph or something...