Evan

Hi all,

After cruising along and coming to a stop, (either shift to neutral or depress the clutch), my idle always jumps up (around 2K rpm) and then settles back down to "normal". Is this how all 993's are?

Also, how do I know when my ISV valve needs to be cleaned?

Thanks.

Evan.

Chris W. - '96 Targa

Never noticed that behavior in mine. The ISV might need to be cleaned if your idle isn't a constant RPM, but rambles around a bit on the tach. The idle itself will not sound steady.

-Chris

Evan

Idle is steady, it's just at a stop. Then back to normal. Huhhh... maybe I'll clean it anyway and see.

What does the ISV do anyway? Do you know?

Thanks Chris

tom_993

Chris,

The ISV bleeds a small amount of air past the throttle body. The computer controls how much air. This is how computer controlled cars idle. Most modern computer controlled cars have an equivalent system. Before these computer controlled systems, the throttle plate had to remain open a small amount to idle. You could adjust this opening with a screw, and speed up your idle. With an ISV, the throttle plate closes tightly and there is no idle adjustment screw.

Tom
’95 993

Evan

Thanks Tom..

Evan.

Greg H.

The ISV on my boat was dirty and the boat exhibited the same symptoms as your car except that it ended up a couple of hundred RPM higher than normal. Cleaning it solved the problem.

Greg H.

Evan

Greg, I'll give it a shot.

Thanks.

Tom W

Think of cleaning it out as a 1 hour bonding experience with your car. It takes most of the hour taking it our or putting it back in the first time. Cleaning takes all of 10 minutes. When you take it out, see if the "gate" inside move freely (it should). If it doesn't then you know you needed to clean it.

Evan

Tom,

What type of cleaner should I use?

Evan.

Greg H.

I used a combination of carburetor cleaner, gasoline and elbow grease.

Greg H.

Chris W. - '96 Targa

I used Gumout carb & choke cleaner, but not sure if that is the recommended solvent. I had no problems with it, though.

-Chris