Hi all
1999 gmc suburban 163000 miles 5.7 vortec.
I had lots of problems with this suburban.
I bought this truck last year. totally neglected.
to get an idea it had the original fuel filter, original o2 sensors.
the guy did nothing to this truck.
New Wires, plugs cap rotor air filter, all vacuum lines checked
after tons of work got it running good with no codes showing or pending.
the last thing i did was change a leaky fuel tank and a lazy fuel pump.

now the truck has great fuel pressure 55lbs holds the pressure nicely.
used sea foam after tank was changed, in tank and loaded in brake booster.

here's the problem now........Gas millage is **** poor....10mpg.
and hard starts cold or hot. Like 6 or 7 cranks of the starter for it to start now. Seems to have lost some throttle power not much.

Again no codes and it runs smooth and idles nice.

any ideas?

i can provide live readings if that helps.

 

You don't mention if you did a general tune up on the truck or not. That would be a great place to start if you haven't already. Plugs, wires, air filter, look for broken/leaky vacuum lines etc.

 

Yea complete tune up was done less than 4 months ago
new air filter wires cap rotor all ac delco parts.
All sensors were replaced as well (most just fell apart)
here are my readings......
IM readiness

When you see check that represents a check mark the scanner gives
N/A means Not available
x means Problem

Mis Check
Fue Check
CCM Check
Cat Check
HCat - N/A
Evap X
Air N/A
O2S Check
HRT check
egr Check

So no codes but the Evap is showing a red x
Is this a problem what should I read with scanner to check EVAP?


Live Data
DTC-CNT 0
FuelSys1 CL
Fuelsys2 CL?
Load_PCT% 2.0 at idle 2000 rpm 9.8
ECT - 193
SHRTF1% 3.9 at idle 2000 rpm -3.1
LongFT1% 14.1 at idle 2000 rpm -4.7
SHRTF2% 3.9 at idle 2000 rpm -3.1
LongFT2% 14.8 at idle 2000 rpm -6.3
MAP(psi) Idle 4.6 2000 rpm 3.9
RPM 640
VSS 0
Spark Adv 23.5
IAT(F) 53
MAF idle 0.01 2000 rpm 0.04
TP(%) Idle 0.0 2000 7.5
02B1S1(V) Floats from .120 to .790 at idle
SHRTFTB1S1 (%) Floats from 1.6 - 3.1 at idle
02B1S2(V) holds at .60
SHRTFTB1S it just says N/A always has
02B2S1(V) Floats from .155 to .825 at idle
SHRTFTB2S1 (%) Floats from 00 - 2.3 at idle
02B2S2(V) holds at .95
SHRTFTB2S2 (%) holds at 99.2

Only problems I see are SHRTFTB1S has no reading n/a
Problem with sensor?