I have a 2000 Olds Bravada that will not rev over 2000 RPM or drive over 15 MPH. I have changed fuel filter. Fuel pump maintains 60 psi, goes up to 65 when revving. I have gotten an intermittent P0300 code (misc misfire) very occasionally but no other error code. Any ideas?

Are you capable of watching live data?

no, i'm not

It'* a long shot, but disconnect the MAF electrical connector start it up and see what happens. It may be a little hard to start, but should stay running.

Exhaust back pressure?

Check for codes?

D

Disconnected the MAF and it made no change.

Sorry it took long to reply but the weather has been miserable here and I don't have a garage right now.

This condition has come on gradually. First it hitched at 55-60 MPH and you had to take your foot off the accelerator to get some power, then 35 mph became top speed, then 30, then 20. What is perplexing is that other than a P0300 code showning up once, there are no error codes

Only other thing I can think of that would cause something like this would be the TPS(throttle position sensor). If they aren't installed correctly, they can cause weird behavior like this. Or if it develops a flat spot, the PCM doesn't know what position the butterfly plate is in. Think of it like the volume control on an old radio. When you turn the volume up and the audio gets scratchy or doesn't do anything, same thing here.

random mifires can be caused by plugged catalytic converter,If you can unhook converter and see if engine can now rev up or better if you can drive.Have replaced many doing this same thing