I have a 97 850 with ~160k miles. New plugs, wires, distributor, rotor and upgraded coil as well as new vacuum tubes etc. I also have a cold air intake with a custom air box to insulate from the engine heat. I also a MBC running that reads a peak of ~ 12-13 psi, but it may be reading low. The stock gauge goes just about all the way to the end of the white which I have read is about 15 PSI.

The car had been running well without any misfire but recently under hard acceleration I have been getting some stuttering right at the 13 psi range. The gauge needle flutters at the same time.

Here are some confounding variables, the stuttering started right when we came out of a major heat wave. The air temp was about 100 and has dropped to 65 at the same time this started occurring. I set my MBC during the heat wave. Could the drop in temperature cause an increase in the manifold pressure and trigger the fuel cut, or is it more likely that I have developed a missfire? One other thing, this has been happening for several days, but my check engine light didn't come on until today. I don't have a reader so I have to take it to my mechanic to check the code.

If any additional info would help the diagnosis I will post.

Thanks for the help

 

I used to hit the fuel cut off on hard acceleration and was running at 14-15 psi. It wasnt until I got my IPD ECU that it stopped. I think they removed that threshold.

 

fuel cut is at 15.5 psi. so i think it is safe to assume that your gauge is slightly off (or your reading it .5 off. and you are hitting fuel cut off. its not odd to see +/- 1psi