RPM Question

[g8nightman]

I have a 94 S4 when a start the car and it warms up my rpm stays at 1000 rpm. But after im on the highway or after some hard driving the RPM stays at 1500 rpm. Is there anything that needs adjusting or do I need to replace a sensor???

Thanks in advance for an help

[PatHeald]

Does your car have a throttle jack solenoid? If so, it may be the culprit....

My carbed '87 displayed similar symptoms.

I just whipped the wires off the solenoid and my tickover no longer has a mind of it's own.

There is an adjustment on the throttle jack which in theory allows you to leave it connected and to adjust the jacked tickover down to something more reasonable than 1500.

There was inadequate adjustment on mine, so I simply leave it disconnected.

Hope this helps.

Cheers

Pat.

[johnwatkins]

The S4 has a vacuum operated throttle jack, the vacuum is produced by a pump loacted behind the panel in the boot (or trunk if you prefer).

The vacuum is controlled by a solenoid which is located on the rear of the boot floor, there's 3 of them in a line.

The solenoids are controlled by the ECM & you should have a sticker on the rear hatch (above your head) which details all of your vacuum connections.

Cheers,

john W
'95 S4s

[g8nightman]

Guys I tried dicconecting the wires from the throttle jack solenoid and it didnt make change the rpm still high also check the hoses to the pump still good anything eles i should look for maybe my pump is bad is there a way to test it ?

[Skerd]

Did you check the IAC valve? One time that was the cause of my high idle. The cheapest fix I ever had.

[g8nightman]

Where is the IAC valve located?

[superdave]

Could also be the thermal ignition valve located in the central body of the carbs/injectors. It's green is colour and made of plastic. This advances your timing on cold start to around 30 degrees and switches back when warm. Mine failed and it was advancing too much all the time. I also think that this may be connected in some way to the throttle jack solenoid.
Also check your purge pump switch? This is located on the aluminium water pipe on the right hand side of your firewall. There are three temperature senders, it's the bottm one. If this fails then, your car thinks it's still running cold. disconnect one of the wires when your engine is warm and see if it makes a difference.
BTW Iam quoting on a UK spec car and carbs. Your car maybe different.

Cheers,


Dave Walters

[cnh1990]

Are you using different brands of fuel?

Sometimes different fuel grades by one or two octane points confuses the ECU and makes it idle weird. If that happens reset it and stick to one brand of fuel.

Calvin