Hey, I have a 1986 iroc that is making strange noises (I describe it as a boiling tea kettle), and the engine idles much faster in PARK than it does in OVERDRIVE while stopped.

Could this be a vacuum leak? If so what is the best way to locate the leak?

 

I think the first thing I would do is run the car and get a funnel with a hose attached to it. Put the other end of the hose to your ear, and move the funnel around in your engine compartment trying to locate the source of the whistling, kind of like a stethoscope. Once you find out what is making the noise, you have a much better chance of figuring out why.

 

Well problem is it only makes the noise at speed... Part of me wants to think its like an air leak in the bodywork or possibly t tops, but I just dont know.

 

Is there a hissing sound behind your dash in the area of the heat/AC levers?

 

You mean the AC heater controls? If so let me check.

 

Yes, whenever I change the setting (max-vent for example) there is a DEFINITE hissing sound. very prominent what does this mean?

 

You probably have the same huge vacuum leak at the heater control valve that every third-gen has until the owner pulls the heater control unit out, and fixes the busted vacuum-control switch.

You will notice a BIG difference in low-end response when you fix that.

See https://www.thirdgen.org/forums/inte...anent-fix.html for discussion of repairing this vacuum leak.

 

That is more than likely a factor, but what about the high pitched whistling that happens at speed?

 

If the sound is coming from behind the dash, its 99% for sure the heater-control's vacuum valve talking to you. A chunk of the smeg ingested by the valve could be acting as a reed, and playing you a sick little tuen.

 

Lol probably. Last thing: The car idles much faster in park than in overdrive, why is this?

 

Until you fix EVERY vacuum leak, and EVERY code, you cannot expect idle to be consistent.

Just be glad you got a computer making rough adjustments automatically. Otherwise, with whatever vacuum or electrical failures your enduring, you would probably also be dealing with stalling if the computer weren't working overtime trying to keep the motor spinning.

 

THANKS! Case closed.

 

Please post back to this thread, and let us know whether the the heater valve repair fixes the problem for you.