- Jul 1, 2013
- 749
Well, last weekend was a four day weekend for me, perfect chance to work on the Envoy!! I had been putting off getting a new O2 sensor and a CPAS for a little while, as the O2 sensor was due to be replaced since the Voy just rolled 101000 miles, and the CPAS had some oil seepage in the electrical connector. Went to my local GM dealership and walked out with both pieces for about $105 (got 'em wholesale 
)
Installation was anti-climatic, the O2 sensor was, as expected, very tight and a pain to get loose. The first few threads looked fouled on it after I got it out, but the new one ended up threading in and seating just fine, so I don't know what was wrong there.
CPAS was easy, the new one is an improved design with some springs over the screens to keep the screens in place. Cleaned out the electrical connector with some aerosol MAF cleaner I had from another project, just kept flushing the little holes until there was no more oil residue coming out. While I was there, I went ahead and pulled fuses 10 and 28 and cleaned the TB for the heck of it. (you know you're a GMT owner when...) It all went back together well and fired up just fine.
Now, I wasn't expecting major differences in anything, as I haven't been having problems with the Envoy, but I was very surprised by a couple of things. One, the gas mileage seems to have increased. I used to use a little under 1/2 of a tank to make the trip from home to school, but this time I only used a little over 1/4 of a tank. Got gas tonight, and the mileage from the trip (almost all four lane at 70-75 MPH, good bit of hills) plus some in town driving here in Morgantown was 17.7 MPG!! I had been averaging 15.5-16, so I got a roughly 2 MPG increase! The other thing I was surprised at was the idle quality. I had problems with rough idle in the past, but changed the plugs around 95,000 and it went away, with the occasional shudder that I just took to be normal, or perhaps crappy gasoline. Since the new parts the idle has been rock solid at 630 RPM with no shudders. Lastly, maybe it's just me, but on the highway when I'm running 70-75 MPH and I want to accelerate, it used to almost always have to shift to third to do it. Now, with the same light foot on the throttle, it will accelerate just fine and never leave fourth.
This isn't really a post with a question or a problem I have (for once). It is more of a report on my findings.
Moral of the story, at 100,000 when you do the plugs, go ahead and drop the coin for the ACDelco manifold O2 sensor and the ACDelco CPAS. The CPAS should be done even before that if pulling the wiring connector off of it finds you staring at an oil soaked connector.
) Installation was anti-climatic, the O2 sensor was, as expected, very tight and a pain to get loose. The first few threads looked fouled on it after I got it out, but the new one ended up threading in and seating just fine, so I don't know what was wrong there.
CPAS was easy, the new one is an improved design with some springs over the screens to keep the screens in place. Cleaned out the electrical connector with some aerosol MAF cleaner I had from another project, just kept flushing the little holes until there was no more oil residue coming out. While I was there, I went ahead and pulled fuses 10 and 28 and cleaned the TB for the heck of it. (you know you're a GMT owner when...) It all went back together well and fired up just fine.Now, I wasn't expecting major differences in anything, as I haven't been having problems with the Envoy, but I was very surprised by a couple of things. One, the gas mileage seems to have increased. I used to use a little under 1/2 of a tank to make the trip from home to school, but this time I only used a little over 1/4 of a tank. Got gas tonight, and the mileage from the trip (almost all four lane at 70-75 MPH, good bit of hills) plus some in town driving here in Morgantown was 17.7 MPG!! I had been averaging 15.5-16, so I got a roughly 2 MPG increase! The other thing I was surprised at was the idle quality. I had problems with rough idle in the past, but changed the plugs around 95,000 and it went away, with the occasional shudder that I just took to be normal, or perhaps crappy gasoline. Since the new parts the idle has been rock solid at 630 RPM with no shudders. Lastly, maybe it's just me, but on the highway when I'm running 70-75 MPH and I want to accelerate, it used to almost always have to shift to third to do it. Now, with the same light foot on the throttle, it will accelerate just fine and never leave fourth.
This isn't really a post with a question or a problem I have (for once). It is more of a report on my findings.
Moral of the story, at 100,000 when you do the plugs, go ahead and drop the coin for the ACDelco manifold O2 sensor and the ACDelco CPAS. The CPAS should be done even before that if pulling the wiring connector off of it finds you staring at an oil soaked connector.