I started to get some issues couple months ago, when coasting along, say in turning lane and need to punch it a bit to beat traffic to turn left I would notice a slight hesitation then a clunk noise. I looked for engine mount problems, I read others having issues like me. I did have front motor mount broke. I replaced it, wondering now if I might replace the rubber in the front top mounts, but I can handle this...
For awhile now I thought I had "Active Fuel Management" because I read it in the manual that came with the car, also because it seems like it cuts down on cylinders when going on the xway at a steady speed like 65 for awhile. It never has a issue at that speed if I need to punch it to pass someone.
Now it's starting to do this between 30 and 45 mph, feels like it goes into overdrive to soon, like I want to drive in 3rd gear all the time on the street. It's ridiculous, if you travel at 35 mph for even 40 seconds it will go into 4th gear and feel like it cuts down to 3 cylinders.If you try and ride at that speed with not much gas pedal pushed down it will kind of shudder a bit (like in a 4 speed cluth and driving in 4th gear at 25/30mph) and then down shift, then shift back up again. Shoot I got to give it gas let off, coast, give it gas again to go at steady 35mph speed.
My vin is 2G1WT58K079355330, can it be told if this car has AFM from vin? I read that it only comes with 3900 motor?
I seen one guy post that he had to drop his tranny and replace the Pressure Control Solenoid and the torque convertor bandwith solenoid. I'm not equipped to drop the tranny, I did it in my old chevels in the 70's and 80's and other cars but this is different in todays cars, plus I don't have the tools and place to do it at. I don't know what to do at this point. The manual said to replace the trans fluid at 150,000 miles. I'm not there but at 146,435. No leaks and very clean under the hood. It's been highway miles, for few yrs drove xway 70 miles a day. I'm up for suggestions and how to read my vin number, what does this mean:
WMI / VDS / VIS: 2G1 / WT58K0 / 79355330
Thanks to anyone who takes the time to read this long post!

 

afm is only on the 5.3L v-8 in the ss model

 

yea I see this now, The manual that came with the car said this. So it must be the pressure control soloniod. Seems in the new ones they have changed when or at what rpms for 1st and 4th will shift. According to what I read. Dag gone shame a 11 dollar part is controlling all this and they want 1000 dollars to drop trans,take off side plate, put new part on and back in. Probably don't take them an hour.

 

Check the seal around the probe in the top of the intake manifold at the MAP Sensor. Mine was leaking around the edges of the probe seal. If it wiggles even a little, then it's leaking. If this is your problem, let me know and I'll share the fix.

 

I sure will try this, I put a new filter in and cleaned the mass air sensor with crc mas cleaner. Thanks I will try this and let you know here on the forum.