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Matt
Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 20615
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have an e39 540i manual and im getting a misfire massivly

Customer Question

Hi i have an e39 540i manual and im getting a misfire massivly when under 2k rpm when accelerating more noticeable from 2nd gear upwards, and it feels like it has a glitch mid rev range too, ive disconnected my maf and been for a drive and it got worse but im unsure if this eliminated the maf or not
Submitted: 1 year ago.
Category: UK Car
Expert:  Matt replied 1 year ago.

Hello

if the car still drives badly / worse with the MAF disconnected

then its unlikely to be the issue

I'd suggest the next step is to check for a lack of fuel and a lack of fuel pressure from the electrical pump at the tank.

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubtand do the same for the fuse,

Ideally measure the pressure at the injectors and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

Expert:  Matt replied 1 year ago.

Hi

do you still need help?

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