Major Engine problem !!

[Lansky'smx6]

Hi , this could be ths strangest problem ever.
Anyway , at a stop street / traffic light. the car will automatically start
increasing it's rev's. I will then place the it Neutral or Park ( Auto transmission) and excellerate hard , but the vehicle will start to backfire , and eventually switch off. It then battles to start and there is a distinct Fuel smell , Like it was flooded.
When started , it drives beautifully. no backfiring. This only happens twice a day.
Has anyone come across such a problem ?
Could it be the computer box , someone mentioned a relay, I decided to come to you guys.

Please advise

Regards

[wolf_funk]

sounds like maybe getting starved of fuel some how

[Parallex]

Sounds to me like sticky butterfly on the throttle body or in the manifold. When its warmed up it will work better, thats why it would only do it twice a day or so. It would also explain the overfuelling as the fuel thats put in is not burnt correctly due to a lack of air.

Thats my first thought without further information.

Ben.

[Russellg]

Moved to the technical area

Russ

[Ian F Chequer]

Does it do it cold or warm?

ifc

[gavroche]

have you had a flashing hold light at all? this may help identify if its a sensor problem. A dodgy vaf sensor can cause similar issues but like ben said it more likely to be ralated to the TB.

I had a similar problem on my first auto six. The solution was simple, remove the negative battery terminal and then press your foot on the brake to deplete any excess electrical charge and then reconnect the battery. This reset my ECU which had somehow got the fuel to air mixture part of its program a little messed up. Its a long shot but worth a try.

You may also want to try "pulling codes" to see if there are any other sensor issues. You wont need an LED, just short TEN to GND in the diagnostics and switch IGN on and watch your hold light for a sequence of flashes.