Losing power at 2500 rpm. Help please.

[bmwstudent]

Check or replace fuel filter, engines require a lot more fuel accelerating under load than they do just revving with no load.

[bloodsnot]

Current problem- I started the car up and drove to the store fine with no issues. On the way home as I was driving the car started to bog out around 2,500 rpm. It happens through out all of the gears. Feels like as once it hits 2500 rpm it's not getting any fuel at all. I limped home like that and with the car in neutral it revs up to red line. Why would it rev high in neutral but not go past 2,500 in gear? Could it be an air leak? Possible the fuel pump?

Short answer is yes, it could be an air leak. Look up the engine->vacuum control diagrams for your car on RealOEM.com and go check all of the hoses on your car for old, hard, brittle rubber and for cracks. You can spray carb cleaner around the fittings as a secondary check or do a smoke test to really rule out air leaks.

I don't think it's the fuel pump because the fuel pump load doesn't vary with engine load on these cars. The system is pressurized by the pump and the variations in fuel demand are handled by varying the timing injector pulses.

It still very well could be a fuel issue and with your mention of poor flowing injectors I would say it's likely that the fuel filter change was long overdue so your entire fuel setup is suspect. Perhaps the fuel pressure regulator on the end of the fuel rail is on its way out.

I would start by testing the fuel pressure by t-ing in a fuel pressure test gauge right before the fuel rail to see if these power loss issues correspond to drops in fuel. You should be able to get the test gauge to rest near the wipers with your hood closed so you or your navigator can watch it while you drive.

If this problem doesn't seem to be related to fuel pressure then I would look to the air flow meter or ignition components such as spark plugs and wires amongst various other things. Do you have a Bentley manual? There are some thorough troubleshooting guides in there.

[Vdubmt]

I picked up this 87 325e 5speed a few weeks ago and it's driving me mad.
History- After I picked it up I had the timing belt and water pump changed. After they did that the tech said that he test drove and noticed a missfire. When he pulled one of the injectors he noticed it was clogged and looked like rust was in the gas. He replaced one plug, the fuel filter and sent all of the injectors out to be cleaned and rebuilt. The car ran fine for the little bit that I drove it in the last two days.

Current problem- I started the car up and drove to the store fine with no issues. On the way home as I was driving the car started to bog out around 2,500 rpm. It happens through out all of the gears. Feels like as once it hits 2500 rpm it's not getting any fuel at all. I limped home like that and with the car in neutral it revs up to red line. Why would it rev high in neutral but not go past 2,500 in gear? Could it be an air leak? Possible the fuel pump?

I've done searches and have seen people with the same issue but can't find any solutions in any of the posts. Please help if you can. I love this car and just want to drive it which I haven't been able to do since I've bought it. Thanks.