At idle, Rennbay AFM in my dash shows stoich for a 1-2 secnds and then drops off the lean side of the scale and then jumps back up. When it drops to lean, the car shudders a little and then smooths when the guage comes up. The guage keeps up this pattern all the time when accelerating or at constant throttle, it just goes through the cycle faster at higher rpm's. I didn't notice the stumble on the test drive, only after the PPI when I picked up the car from the seller it was doing this. This is on an 87 951

 

btt

 

How's the O2 sensor? I know they get slow when they age. Just a guess.

 

FPR?

-Mark

 

What's FPR?

Haven't checked the 02 sensor yet. Where is it. I'm still a real newbie on wrenching.
My first thought was vacuum leak, I bought a vacuum guage but I haven't figured out how to use it yet. Where's a good place to hook it up to check the vacuum system?

 

Fuel Pressure Regulator. Sorry.

-Mark