TIEyota fighter ace
Join Date: Sep 2005
Location: Washington State
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Best way to get rid of carbon buildup? Get a can of Seafoam, run it through the brake booster line or there's a can now that has a bendy straw so you can inject directly past the throttle plate via the air hose on the manifold...do a search for Seafoam, there's a ton of posts about it. It'll make a nice smoke show, the one thing to remember is don't let the engine die until after you stop injecting it (hydrolocking is bad).
If you want to avoid making your engine breathe kerosene, you can do the same thing with steam-distilled water via a very shallow bowl and a steady hand on the intake hose. This may require two people, one to apply throttle and make sure the engine doesn't stall out and one to manage controlled suction. Don't use tap water, you don't want all those minerals deposited on your pistons. Basically the water flash-boils into steam in the combustion chamber and the pressure blasts the crud off, plus it brings down the combustion chamber temperature. (High-boost turbocharged cars use water injection for the bang and for the charge-cooling effects as well). This method produces less kerosene smoke and is cleaner and cheaper with the same effect and no damage unless something else is badly badly wrong. (I ran a half-gallon of water through my engine in about 10 minutes and got a CEL for one sparkplug misfiring once.) If your Prizm has the well-known oil consumption issues (rings/seals on the 7AFE, primarily), then you've probably got a lot of buildup and this will give you a little more power, improve your idle, and slightly increase your mileage, otherwise it's just easy troubleshooting.
You CAN do the Marvel Mystery Oil / B12 / GM Top Engine Cleaner approach where you take the plugs out and pour a capful of that down onto the pistons and let it sit overnight, then pull the EFI relay in the morning and crank the engine over to let it spit out the excess and build back up oil pressure, then put the plugs back in, the relay back in, and start 'er up...but that can be a little nerve-wracking as the engine tends to be reluctant to start afterward.
Of course it could be a dirty throttle position sensor, in which case none of the above will be of any use to you and you'll have to either get some specialized tools to recalibrate it or pay somebody else for that privilege.
---- Bug, 82 TE72, 3TC/A40
-------|- Jezebel, 96 AE102, 7AGE/A245E
Last edited by Piloter; 09-12-2010 at 06:02 PM.