sc 400 stalls at start

[michael]

My 92 sc400 stalls at start up unless I have the air conditioning on. Once the car is running I turn the ac off and all is well, car drives perfect, never wants to stall with ac off at stoplights. Only when I first start the car, if I have the ac off the car at start up will start perfectly and then within a second or two the idle will just slowly trickle down and die within 10 seconds approximately. Does anyone have any ideas on why I would have to have ac on at start up and what the cause or problem is. Thanks

 

[Gazzasore]

It could be your fuel pump ECU

 

[Zuffen]

The ECU has an idle up feature when the air is on to stop the engine stalling or just idling low. A little like the power steering idle up only electronic.

Because the air is on the idle speed is higher and it doesn't stall.

I'd try cleaning the ISCV and see if it works. This is a cost free fix that may work.

 

[michael]

I cleaned the idle cotrol valve, I did it exactly as desribed per a link I was sent via this sight. It's got to be something else. My best guess at this point is that it is the fuel ecu, has anyone had a similar problem due to a bad fuel ecu, or does the fuel ecu control start up?

 

[Zuffen]

The fuel ECU doesn't control start up. Me main ECU tells the fuel ECU what to do. When starting it will usually run in hi speed mode to get the fuel pressure up initially then it will drop down.

Try bypassing the fuel ECU and see what happens.

 

[sc400rayray]

it might be the fuel fillter, or anything with your plugs- they tend to go bad after the 8 year mark, mine did the samething try to start it would bog then turn off, i got new caps plugs wire and a fuel filter, works good now- get the good plugs off this site i think the are a better buy