jerking and loosing power

[Ariel525i]

The car started off this morning just fine. After about 2 kms the car started jerking and lost power. I stepped on the accelerator but there was no response till after 2 seconds. The car would then accelerate then after a few meters would loose power again. At this point I would have to drive real slow till the power comes back. After another 5 mins of being in this situation, the car drives fine again till I get to the office which was about 5 kms away. On my way home, the car runs fine again for about 2kms then starts with the jerking and loss of power. The power response goes on and off for about another 10 mins then drives fine again till I get home.

What could this be? I just got the car back 5 days ago from the bmw dealer for a change oil and change of crankshaft oil seals. I'm thinking maybe a clogged fuel filter or faulty fuel pump. My idle is very smooth and stable at 800 rpm.

Feedback please!!!

[BillionPa]

loss of pressure under power with smooth idle is generally indicative of a fuel pressure problem, borrow in inline meter to test the pressure.... your car doesnt have EWS does it?

[Flamin'Cow]

Did you check the milage after you got the car back from the dealer?

Sounds like either a fuel problem or possibly one with your distributor - check the cap...

If the car was running fine beforehand - I suggest you take it back to the dealer and ask what they have done to it!

[Happy_Go_Lucky]

The car started off this morning just fine. After about 2 kms the car started jerking and lost power. I stepped on the accelerator but there was no response till after 2 seconds. The car would then accelerate then after a few meters would loose power again. At this point I would have to drive real slow till the power comes back. After another 5 mins of being in this situation, the car drives fine again till I get to the office which was about 5 kms away. On my way home, the car runs fine again for about 2kms then starts with the jerking and loss of power. The power response goes on and off for about another 10 mins then drives fine again till I get home.

What could this be? I just got the car back 5 days ago from the bmw dealer for a change oil and change of crankshaft oil seals. I'm thinking maybe a clogged fuel filter or faulty fuel pump. My idle is very smooth and stable at 800 rpm.

Feedback please!!!

I had a similar problem some time back with my 1990 535. What is you fuel level like, are you running below quarter? I found that I had this problem below quarter tank, and usually up hills. After many hours of searching, pulled the pump from the tank. The crimped aluminum housing had cracked around the top of the pump. As the fuel get below this mark (especially up hills), she's suck air, causing the jerk. Replaced the pump, sorted! Good Luck.:)

[Morgenster]

Maybe it's something as simple as the fuelpump relay?
Intermittent unpredictable troubles are usually electrical.

[Ariel525i]

I had a similar problem some time back with my 1990 535. What is you fuel level like, are you running below quarter? I found that I had this problem below quarter tank, and usually up hills. After many hours of searching, pulled the pump from the tank. The crimped aluminum housing had cracked around the top of the pump. As the fuel get below this mark (especially up hills), she's suck air, causing the jerk. Replaced the pump, sorted! Good Luck.:)

Actually my tank level is at 2/3 (6oL mark). Will try to take a look at the pump as well.

[Ariel525i]

Maybe it's something as simple as the fuelpump relay?
Intermittent unpredictable troubles are usually electrical.

Which is the fuel pump relay?

[Ariel525i]

loss of pressure under power with smooth idle is generally indicative of a fuel pressure problem, borrow in inline meter to test the pressure.... your car doesnt have EWS does it?

Excuse my ignorance...but what is EWS?

[BillionPa]

bah, meant to say EML.

thats what i get for posting after i have been up 19 hours with barely any food.

anyway, EWS is part of the security system.

EML on the other hand is a type of electronic throttle, and malfunction of the drive motor can cause the symptoms displayed.

[Ross]

Sounds like it's starving for fuel, as in a clogged filter or cavitating pickup. Maybe a dying pump. An electrical gremlin, like a relay will more likely shut it down altogether.
If your fuel filter hasn't been changed in recent memory start there.