My buddy is having problems with his 1990 305 TPI. When the motor is cold it runs for a few seconds and then goes dead without pushing the accelerator pedal. When it is warmed up after 5 or 10 minutes the problem is gone.

The readings from the coolant temperature sensor seem to be ok.

What we have found out is: with pulling the vacuum hose from the brake booster the engine is running fine...

Thanks for your help...''

 

That is not a good idea to pull the vacuum hose from the brake booster while the engine is running. Did you get any trouble codes, have you checked the O2 sensor?

 

It happened by mistake...

No, we are getting no trouble codes, and we haven't checked the oxygen sensor. But as far as I know the values of the oxygen sensor are not important during the cold start which means open loop mode.

Is this right?

 

You're correct. The O² sensor basically only plugs the leak in the exhaust pipe when the ECM is in Open Loop Mode.

Removing the vacuum line whiole idling and having it result in a better operating condition indicates a very rich mixture. Hvae you tested fuel pressure?

 

Vader, thanks for your reply. No, we didn't check the fuel pressure...but we will do it.

 

If the pressure is off...you may have 1 injector that is leaking...when in cold loop, it runs at pre programmed settings that tell how long to run injectors...one the open loop starts, the computer leans out the rest of them to compensate for the possible leaking one...

check your plugs to see if one is really black (sooted) and if so, try replacing that injector.