Tuning Info

[sam_pon]

I think you may have a problem with the EVAP system (it may have an air leak), it needs to be diagnosed.

dear joecar

i have a OBD2 Cable , could you advice me with a good software to diagnose my car , or this diagnosing must be through the dealer shop ,

thanks in advanced for your help .

[sam_pon]

dear joecar

i have a OBD2 Cable , could you advice me with a good software to diagnose my car , or this diagnosing must be through the dealer shop ,

thanks in advanced for your help .

dear joecar , i am so sorry if my question was stupid question , or i asked it in the wrong place , but as you see i am new for this job ( tuning ) , so if you just lead me to the right way i will appreciate that so much .

thanks in advanced .

[joecar]

Which OBD2 cable do you have...?

Do you have the GM Service Manual for your 2003 GMC Envoy (this is required for diagnosing problems)...?

Have you done mechanical work on your 2003 GMC Envoy (you must be familiar with general procedures/methods/tools)...?

[sam_pon]

this cable :

and i have the service manual for the envoy from 2002 to 2009 in one manual ,
i made many simple things to my car , like changing spark plugs , replace fan clutch , replace brakes pads , cleaning throttle body , changing heating sensor , changing thermostat ... etc

that is all about me , and i am 38 years old , started loving mechanical works from about 20 years .

but i am consider my self a beginner till now .

i am waiting for your reply

thanks a lot

[joecar]

Did it come with software...?

Is it ELM327 compatible...? If it is, Google "ELM327 software".

. . .
i think there is some problem at gas pump , because when the tank full , the acceleration is very bad , or what you think ?
because i noticed that when the a/c working the acceleration is bad also .
. . .

. . .
and i have the service manual for the envoy from 2002 to 2009 in one manual ,
i made many simple things to my car , like changing spark plugs , replace fan clutch , replace brakes pads , cleaning throttle body , changing heating sensor , changing thermostat ... etc

that is all about me , and i am 38 years old , started loving mechanical works from about 20 years .

but i am consider my self a beginner till now .
. . .

Ok, good...

In the GM Service Manual, for your vehicle (2003 GMC Envoy), goto the Engine section, find the Description subsection, read about EVAP (and the other systems)...

then look thru the DTC pages (for your engine) and look closely at the DTC for the EVAP system;

you will have to test your EVAP system for a leak...

if it is leaking air, then it will cause acceleration to be poor (fuel mixture too lean)...

or it may be allowing fuel to be sucked from the tank which will also cause accleration to be poor (fuel mixture too rich).


The GM Service Manual will be your guide, read thru all the various Description and DTC sections to understand how the various systems operate.

Also look at the Engine Control circuit diagrams.

[joecar]

http://en.wikipedia.org/wiki/ELM327
http://scantool.imechatronics.com/downloads.htm
http://www.youtube.com/watch?v=VA-T2qm0lsg
http://www.youtube.com/watch?v=DNUaSp1bRnc

[sam_pon]

thanks my dear for the very useful links , i will try more than one software , to see what is better for diagnosing my problem .

thanks a lot , and have a good day

[joecar]

Also, measure the pressure at the fuel rail, and check if it agrees with the pressure specified by the GM Service Manual.

You have a good day also, let us know how you go.