My 06 Impala 3.5 has 115,000 on the clock. It gets decent mileage (22 city / 29 highway) but has always been sluggish in performance. This includes early up shift (all gears) and have to nearly got WOT to get downshifts. Recently replaced the MAP sensor and wow, all the problems disappeared and the car ran great for a week or so. Now it's back to the old way with poor performance etc. Does this sensor need to seat tightly into the intake? I'm stumped, help please.

 

Did you disconnect the battery when replacing the MAP?

 

You know I didn't and I know better. Gonna do that now. Will let ya know.

 

Well, I was thinking the disconnecting the battery caused it to run better for a week. But if you hadn't..then it shouldn't do anything?

Check all your vacuum hoses for dry rot and cracks.

 

I had a bad fuel pressure regulator cause me the bogging symptoms on my 2001 Impala

 

I did it anyhow. No difference. I did however, put a couple of washers under the bracket that was meant to hold it down and pow there it's running close to where it should. Was there a grommet that received the MAP sensor probe in the top of the intake? I'm thinking of trying to seal off the edges of the sensor to make it vacuum secure. I'll let you know the results. BTW, thanks for your help and interest.

 

Examined the top of the intake. Looks like it needs a seal or gromet to house the sensor probe end. Called the local Chevy dealer and $6.76 later and there will be a factory gromet appearing on Wednesday (none available in all of Albuquerque). This seal has never been in this vehicle. No wonder it ran so sluggish. Wonder how many more folks have this same problem and don't know it? Will let you know mileage and performance on Friday.

 

Wrong seal so I didn't buy it. Seems like it is a gromet built into the intake manifold (they only wanted $1700 for the manifold. Gonna jury rig something to mitigate the vacuum leak around the sensor probe/seal. BTW, mileage went up 2 MPG and performance (timing and downshift improved). Although minor, gotta stop the vacuum leak.

 

Is this the part? looks like it includes the rubber grommet ...

 

Yes that's it. The intake manifold has a hole that is just a bit larger than the red rubber gasket. I used some silicone (auto grade heat resistant) to make a gasket around the base of the sensor and let it cure. Can't believe the difference! Downshifts are crisp and can feel the timing come in during hard acceleration. Used a washer to slightly wedge the sensor in place with the bracket above it. Added 2 mpg in town too but it's hard for me to keep my foot out of it now.