Strange Clicking Noise from Throttle Body

[Richard Hamilton]

This is my brother's 1999 C4 Tiptronic Coupe (UK Car).

The problem started a couple of days ago. When he switched on the ignition there was a strange, continuous, clicking noise from the engine bay, and the engine cranked but wouldn't start. After disconnecting the battery and leaving it for an hour, the engine fired up straight away and runs perfectly.

This morning the clicking appeared again, but it wasn't continuous, and the car started and runs fine. Now when you switch on the ignition it may or may not happen - it seems to be random. The noise seems to come from a device on the side of the throttle body, shown by the red arrow in the picture.

We have checked the connection to this device. There are no faults in the fault memory. The best way to describe the noise is similar to a relay clicking on and off, but a bit louder - almost a buzzing/flapping sound.

Anyone had the same problem?

[Tool Pants]

All I can say is it looks like the idle air control valve also used on an e-gas Boxster that you see in Loren's hand.

[Richard Hamilton]

Have you ever taken the idle control valve off one of these? I know it has been done on non-eGas cars, but I'd be interested to know if there is anything servicable/cleanable inside before we go delving into it.

edit: Looking at it again, the device must be the throttle actuator itself - there doesn't seem to be an idle control valve.

Edited October 19, 2006 by Richard Hamilton

[PTEC]

1999 C4 should be egas, so there no idle air control valve. A clicking noise is normal if you leave the key on for 10 seconds I think. This is the throttle plate adapting. It should only last for a few seconds though. Its sounds like yours may be intermittently malfunctioning.

The red arrow points to the drive mechanism for opening and closing the throttle plate.

[Richard Hamilton]

Just to write a conclusion to this, we fitted a new throttle body today, and it fixed the problem completely. We then stripped down the old unit, and found that the connectors to the actuator motor were slightly corroded. We cleaned them up, but didn't go to the trouble of swapping it back. I get the feeling it would work, but didn't want the hassle of checking.

The new throttle body was 140.00GBP, which is amazing compared to the MAF I bought recently at 149.00GBP. I have no idea how Porsche calculate their prices - the throttle body must cost at least twice as much to make as a MAF! And they can't sell anything like the same quantity. There doesn't seem to be any logic to Porsche spare parts prices at all.

[dbmies]

I had the same problem (2000 w/ 90k miles) but cleaning the throttle plate resolved it for about 6 months. The plate was gummed up on the back side (could only see when pushed open). As noted above, when the plate finds its center point, the centering (clicking/vibrating) process stops.

The centering difficulty and clicking re-appeared recently - I took the air box off and found both sides of the plate to be clean, though blasting the pivot pins with carb cleaner made it stop. Hopefully that is enough to solve the problem, though I may have to replace my body at some point too.

Some background info - I had a bad air/oil separator that I let go too long and was likely sucking some oil into the intake. I speculate oil on the downstream side of my throttle body as the source of this body plate contamination, though have not had time to pull it apart to investigate.