Weird one

[scuzzbat]

So my MX5 is cutting out under semi heavy breaking. My guess is that it could be a fuel pump issue but I'm not sure. It doesn't seem to be an electronic issue. The engine light and the battery light come on and the motor stops. Anyone ever experienced this.?

[Steve]

look for an air leak somewhere after the airflow meter first, or cracked vacuum pipe off the intake manifold.
Otherwise maybe the CAS, plug leads, fuel filter.

*edit - meant to ask, when it cuts out, are your lights/radio etc still working? Have you checked your battery cables are tight?

[MX5Spares]

Alternator issue ??? may not be charging enough or seizing waterpump or alternator ??but check for pipes off drawing air in to engine apart from airflow meter

[scuzzbat]

I'm not sure if its the alternator as the car starts no problem. The dash lights tend to go off from time to time so I think it's a wiring issue. Is it impossible that the cut outs are cause by a dodgy fuel pump?

[MX5Spares]

Unlikely but the rectifier in the alternator may be dodgy loose battery connections,loose alternator connections,bad earth/ground on body ,loose contact on back of ignition switch etc

[Steve]

maybe try , wiggle the ignition switch when its running

[sidewaysreilly]

this is loose wiring, or an intermittent short. Start the car , check the wiring from the back first(battery and mounting) fuel pump etc but make sure to check all earth straps especially the ones on the ppf linking g'box to Diff and all earth around the engine bay. Be careful of rotating belts pulleys etc. They call it a wiggle test at Caterpillar but it will find the problem if its wiring related.

[Diarmuid]

Could be Idle control Sensor or possibly even TPS sensor I had to replace mine a few years back. Unfortunately very hard to test either

[scuzzbat]

I think it's definitely a wiring issue. I had a wiggle at the terminals and wires an it hasn't happened since. Thanks for the advice.