Horrible Acceleration

[troxclair88]

2005 Chevrolet Tahoe 4.8 Liter V8

Whenever I change my engine oil, i have great acceleration power for about 300-500 miles. After, my acceleration power decreases drastically. If I'm on a flat road, I have to wait about three seconds for a response from my engine. If I am on an incline, I have to wait eight to ten seconds for a response. Sometimes even longer. I know that I have a check engine light on with an error code for an evap leak. But the light is on right after I change the oil too.

What can be causing such a drop in acceleration power? What can I do to not make it drop? I just simply want great acceleration power constantly. Help?

 

[troxclair88]

Anyone have an idea(s)?

 

[Kenny D]

Any difference in your oil pressure between oil change and 500 miles? Have you tracked down your EVAP issue? I would solve the EVAP issue and then see if it still happens.

 

[troxclair88]

Sorry for the delayed response.
I switched out my purge solenoid. CEL stayed off for awhile but eventually came back on. No further success with evap leak.
There is no pressure change.
This has me stumped..

 

[Danny3737]

I seriously doubt your issue has anything to do with just changing the oil. I would first check obvious things like unplugged or cracked vacuum hoses, plug wires, etc.

 

[troxclair88]

I've had the vehicle tested at a small local shop. Something they called a smoke test. Hooked some canister up said smoke would come out where the evap leak was. No luck.

I've sprayed every vacuum hose I can find with carburetor cleaner while the engine was running to see if it raised the acceleration. No luck.

I don't know what else to do in reference to that evap leak except ignore it (only if I could, huh?), bring it to a dealership, or keep praying that I find it myself.

Could you evap leak really cause no decreased acceleration for a little and then the decrease?

Like I said, stumped right now...

 

[troxclair88]

Only current error code:
P0449
Description: EVAP purge/vent solenoid circuit malfunction

 

[Danny3737]

CATS maybe?

 

[Kenny D]

Only current error code:
P0449
Description: EVAP purge/vent solenoid circuit malfunction

Have you changed the vent solenoid? If so, maybe check the connection and wiring for shorts.

 

[Smrtss1]

CATS maybe?

Wouldn't CATS be throwing a code or causing it to go into full time limp mode? O2 sensors would be throwing codes