stalling 350i

[pipe strangler]

hi recently purchased 1988 350i tas,when the cooling fans cut in when in traffic or stationary the revs die and the engine cuts out. Any body have any ideas to what the problem is and what to do to fix it.
pete

[dwgriffith]

My old wedge had the same problem, it turned out to be one of the cooling fans needed replacement as it was pulling around 20A instead of 5A. The extra load on the alternator was enough to stall to engine.

[pipe strangler]

thanks for the advice that makes sence because the second the fan cuts in the engine dies.

[Mr Tank]

Hi

What are the engine revs on tick over when its warm? You could just raise it a little to compansate, until you replace the fans.

Andy

[pipe strangler]

hi andy, engine ticks over at 1200rpm when warm have a feeling previous owner might have already tried this, am i right in thinking tick over should be 8000rpm.

[alex290568]

Too many zeros I fear. Tickover at 8000rpm would cause many more issues than you currently have!! You are correct in thinking that ticking over at 1200rpm when warm is too fast. Previous owner has probably already tried to resolve the stalling problem. Cheers Alex

[Mr Tank]

Hi

Change the fan! And then see what happens!

Andy

[honestjohntoo]

At a rather high 1200 rpm, the engine torque should be more than enough to overcome the additional electrical load on the battery and charging system.

Apart from a grossly shagged fan that oughta blow a fuse, to my way of thinking you have two possibilities.

1. the extra current being drawn is dropping too much voltage from the battery/charging system due to a fault there-abouts or a bad earth connection on the 'chassis to earth' strap. The flagging voltage is then affecting the electronics in the ignition and/or fuel injection circuits.

Test by measuring the battery voltage when the fault occurs. The voltage drop should be less than 0.5 volts, relatively insignificant. However a drop of (say) 3 or 4 volts may not be acceptable.

2. serious loss of torque at idle can be due to a rogue air-leak into the plenum chamber weakening the mixture to the point where any small extra load kills the engine.

It may also explain why the PO set the idle rpm so high, way above the typically recommended 800 - 875.

Check for air leaks as per page 3 onwards of the pdf available here:

http://www.vintagemodelairplane.com/pages/Rover_Te...

For the record my T.P. idle is set to about 675 rpm and hardly stumbles when the two A/C fans cut in, and they ARE a heavy load.

Air leaks kill torque - "look after your plenum and your plenum will look after you!"