535i (89) backfire

[Pdtuning]

Iv an 89 535i and it has been liyin up for the past 8-10 months, started ok with jump leads but when i went to give a little throttle it started struggling then pop/bang blew the back box to pieces. Started it again and left it idleing witch is fine thinkin that the problem might be the plugs so at half heat (the plugs been hot) i tryed again only for the same problem with popping.

But when i give excelorator slowly it reves fine its only when sudden exceleration that it hesatates and bangs.

Any ideas???
A good can of carb cleaner might do the job but where?

[Dr. evil]

sounds like a rich mixture to me.

[Jon K]

sounds like a rich mixture to me.

Doesn't necessarily have to be rich - if the timing is off, the spark is not reaching fuel and the fuel is finding its way to the manifolds. Then, should the spark catch, the hot exhaust blows past the exhaust valve igniting the fuel in the manifold. Bang.

[Pdtuning]

No a rich mix maybe but if it is its due to a sensor giving a wrong reading, but witch sensor should i clean?

[Paul in NZ]

check your distributor cap and rotor,if it has ben sitting there may be moisture in there from condensation.

[WaaD]

Having same problem on m50 525i , but it only ocours on 1000-1500 rpm full throtle.
Changed spark plugs, but no cure.
Othervise engine idles smothly and accelerating strong.
Get's realy annoying every time pulling in 1'st gear.

[Ferret]

Take off your airbox hose so you can get at the MAF - start it up and make sure the flap is moving smoothly, give the flap a careful poke and make sure it's not sticking in an open position. If the cars been sat for ages, some crap could easily be causing it to stick open, causing the car to run rich.

In fact - unplug your MAF and start the car up (it'll be hard to start) and see if it does the same thing...

[WaaD]

Take off your airbox hose so you can get at the MAF - start it up and make sure the flap is moving smoothly, give the flap a careful poke and make sure it's not sticking in an open position. If the cars been sat for ages, some crap could easily be causing it to stick open, causing the car to run rich.

In fact - unplug your MAF and start the car up (it'll be hard to start) and see if it does the same thing...

Youre so right, after cleaning maf ,car runs like new.

Thanks a lot !

Regards

[Ferret]

Youre so right, after cleaning maf ,car runs like new.

Thanks a lot !

Regards

Jackpot!