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Old 11-17-2012, 02:49 PM   #35
Registered User
Join Date: May 2012
Location: Nw fl
Posts: 61
My Ride: 2003 325Ci
Originally Posted by jfoj View Post
Here is my theory, if you think your fuel pump/filter is giving you problems, for the $125-$160 you should probably replace the pump & filter.

Even if it does not resolve your issue, you have eliminated a typical failure point in the car and can then focus on other issues. The pumps soft fail and many people are surprise on the improved performance with a new fuel pump.

Also make sure your fuel pressure regulator vacuum lines are in good shape, both under the car and at the F connector on the upper intake elbow.

DISA, VANOS seals and MAF can also cause issue, however, the fuel pump is probably the cheapest and easiest thing to rule out. VANOS seals are not expensive, but add the valve cover gasket and the time to do the work, it is the most complex repair out of the 4.

DISA is an easy check and is about $175 for a replacement. MAF is close to $200 depending on which one.

The car is 9 years old, it is worth refreshing sensors as they do not last for ever, but a refresh is probably much cheaper than a new car and if you can DIY, most of these tasks are not too difficult.

I forgot to add that I have replaced the fuel filter and the pump. Still drives exactly like before. I'm lost on how to measure the output voltage from the dme itself, I don't want to power the unit on with the harness in plugged to get probes to it and I really don't want to press through the wires to get the voltage either.

I will be taking the car out of town for about two months on business, so may be I can read up on it more while I'm gone.
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