BC

Warm Start issues on an S4.

ISV checked, tested good, and cleaned.
New Hall sensor
New Crank Sensor
Cleaned Injectors



Characteristics - Cold and warm - car starts perfectly fine. Revs fine as well...

BUT - when you start the car when hot/warm - it will start, idle, and gradually lose revs, try and recover, surge a bit up and down below 800rpm, and occasionally die.

The car can easily be restarted. It may do this again, or may idle fine again. If you attempt some throttle during this hissy-fit, its a but unhappy, but it makes it "go away" quicker.

Any ideas outside of what I have already mentioned as replaced or tested?

Please don't say any two letter words starting in L and ending in H.

Hilton

Checked the Temp II sensor both at the pins and the ECU connectors?

When the problem goes away, does the idle behave normally? (i.e. stable 675rpm and only minor dip below that coming off throttle)

BC

Yes, and Yes mate.

John Speake

Is the throttle closed switch working correctly when warm ? Check the throttle cable isn't too tight.

BC

New TPS, and I can hear the click when the throttle is just opened. Thanks John.

John Speake

Fuel pressure holds up OK after engine switch off ?

BC

I believe i checked that, but that was before all this most recent work where the injectors were cleaned, etc. You are thinking leaky injectors? I believe I ruled that out previously. But it never hurts to double check.

It STARTS fine, but the idle deteriorates for a few minutes or a minute, and then is fine.

Mongo

Does the car crank slow on warm starts? I just have to know this tidbit of info.


I had a problem where a bad fuel dampener was pushing too much gas into the vacuum lines and causing an overly rich warm start which played with the idle.

BC

Fuel Dampers have been checked previously, no fuel coming out. The starting speed when warm is still fast like cold.

Mongo

Thank God it's fast when warm.

For some reason this does not sound like a failing LH. How does your wiring look on your MAF harness. Also, have you cleaned the LH and EZK grounds under the dampener and fuel pressure regulators at the rear of the engine? Polishing these to a shiny copper look did miracles for my issues also.

BC

That was all cleaned when the intake refresh job was done.

John Speake

Some cars need an application of a diagnostic tool, to run the "idle adaptation" routine....

BC

I had a hammer, but it did not hook up properly to this 91. Wouldn't a dis-connect of the battery also do this?

Its something that has persisted past alot of parts replacement and rejuvenation.

John Speake

Battery disconnect isn't the same thing. Battry disconenct removes adaptation parameters. Idle adaptation sets up the idle paramters to suit your particular car.

Does the car have stock chips in the LH and EZk ? Seems strange the Hammer wouldn't connect to it.

BC

At first it had autothority, but I have switched them back to stock. Maybe it was a spanner. Can't you do it with the jumper-ing of the diagnostic port + Dash info toggling?