Harry, If I remember correctly, and anyone can correct me here, but if you take a can of carb cleaner and spray it around the hoses, connectors and such, if the engine idle changes dramatically, then you have found your leak. The idle won't change for long, but it will change. My guess is you will know it when and if you do find a leak. Isaac
Hello hello.
>
> The car is my '94 Chevy Caprice LT1 9C1. It has about 160k miles, and
> in the past few months the ignition system has been almost totally
> replaced (Optispark, wires, plugs), new oxygen sensors, all filters,
> throttle body cleaned, EGR valve, and probably a few things I'm
> forgetting right now.
>
> The computer has been complaining about a high reading from the MAP
> sensor for a while now. I have replaced the sensor with a new Wells,
> and the result is the same. Replaced the charcoal canister purge
> valve (code for that too), but the computer still sets the code for > MAP High.
>
> The symptoms include pinging on acceleration when hot. I have been
> running 89 instead of 87 octane recently, which reduces but does not
> eliminate the pinging. It runs the same as always until it is hot.
> The CEL comes on occasionally, and stays on for a minute or two.
> Sometimes it will only come on once an hour or so, other times it will
> come on every few mintues. It seems to come on when the throttle is
> closed, and usually goes away when it's opened. Also, when hot, the
> idle is somewhat erratic, kind of hunting. It seems to be worsening > over time.
>
> Anyway, all I can think is a vacuum leak somewhere. I have checked
> the various vacuum hoses (many of which I have replaced in the last
> year), but have found nothing bad. TB gasket is new. I tried
> spraying the area with a little parts cleaner to see if the idle
> changes, but didn't notice any different. Any suggestions for
> locating the vacuum leak? Any alternate explainations? I've been
> living with this for a few months now, but would like to finally get > it fixed.
>
> Thanks in advance...
>
> Harry