Hi folks, I have a 81 528i manual, CA car (Completely stock) that ran great a year ago. It was reclaimed with the help of 2 other 528i donors and G-son's help. Now with next G-son, and here is the problem for you "detectives". It starts, runs and idles smoothly, but not much power. When we drive off, it has about 20% of normal power, but still runs smoothly. Data: Timing set to spec (mark at 2200 rpm), good compression (160, 159, 154, 160, 157, 142), good fuel rail press (31 to 39 psi), new fuel filter. Eng vacuum (idle =15 inHg), but goes to zero with full throttle (and very little power up a hill) Free revs to 4500 and still smooth. Cat replaced 3 yrs ago; muffler stock. Running out of ideas. Help!!
Rich in Moraga, CA. Near San Francisco
Reviving 81 528, runs, but no power, Any ideas?
Re: Reviving 81 528, runs, but no power, Any ideas?
Perhaps the AFM flap (vanemeter) is stickySP250rich wrote: Sat Aug 01, 2026 11:42 am Hi folks, I have a 81 528i manual, CA car (Completely stock) that ran great a year ago. It was reclaimed with the help of 2 other 528i donors and G-son's help. Now with next G-son, and here is the problem for you "detectives". It starts, runs and idles smoothly, but not much power. When we drive off, it has about 20% of normal power, but still runs smoothly. Data: Timing set to spec (mark at 2200 rpm), good compression (160, 159, 154, 160, 157, 142), good fuel rail press (31 to 39 psi), new fuel filter. Eng vacuum (idle =15 inHg), but goes to zero with full throttle (and very little power up a hill) Free revs to 4500 and still smooth. Cat replaced 3 yrs ago; muffler stock. Running out of ideas. Help!!
Rich in Moraga, CA. Near San Francisco
Re: Reviving 81 528, runs, but no power, Any ideas?
Could be the cat. They can plug up and get restricted causing a lack of power.
Mike W.
02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
Re: Reviving 81 528, runs, but no power, Any ideas?
Thanks for the hints, so far.
Have checked the AFM. Flap moves smoothly. Smooth/even driving response, just no power.
Cat. Is there a way to check this? What should the back pressure be? Assuming I can use the O2 sensor port to add a pressure gauge. Or is there a simpler approach?
Rich
Have checked the AFM. Flap moves smoothly. Smooth/even driving response, just no power.
Cat. Is there a way to check this? What should the back pressure be? Assuming I can use the O2 sensor port to add a pressure gauge. Or is there a simpler approach?
Rich
Re: Reviving 81 528, runs, but no power, Any ideas?
Actually just removing the O2 sensor is supposed to bring a noticeable improvement. When mine was plugged, it was restricted with low power, but fully driveable, I could even tow my little trailer, so it was hard to get a conclusive back pressure reading. Search the 'net, there's plenty on it.
Mike W.
02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.