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Re: boost problem Posted by Ari [Email] ![]() ![]() In Reply to: boost problem, murph, Thu, 31 Oct 2002 00:46:22 Members do not see ads below this line. - Help Keep This Site Online - Signup |
When you say boost half-way, I assume you mean about half-way into the yellow.
You get full boost with the APC solenoid out of the circuit. I know your first thought is to replace the solenoid, but don't shoot the messenger. The solenoid might just be doing what it's supposed to.
Check out the boost diagnosis FAQ at Townsend Imports - (http://216.78.172.244/turbo_folder/baseboostdia.htm)
By energizing and de-energizing the solenoid, you can test it for flow by blowing air through the various ports.
The solenoid gives you full boost when it's energized, and base boost when it's de-energized (off). So it can be de-energized for a bunch of reasons. The most obvious reason is that your engine is actually knocking, and the APC is doing exactly what it should be doing - cutting back boost to protect your engine. You might be on the hairy edge of knock, and when the engine warms up and leans out a little, you get knock, and the APC kicks in.
If you aren't running 92 or 93 octane fuel, run a tankfull and see if that helps. If you get full boost with better fuel, there are two options - (1) run better fuel, and (2) tune your car up. Old spark plugs, clogged filters, all can contribute to knock. However, some engines can't get full boost unless you're running 91 or 93 octane.
If full octane fuel doesn't do the trick, there may be other things causing knock. This could be carbon buildup, lean running, etc. A long list.
There are a lot of things that can cause low boost. Start with the basics, and get back with the results -we can go from there.
Good luck!
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