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Pressurized Fuel Rail Flush

No guarantees are made on the results, and anything you do yourself is at your own risk.

By Wes Stinson

One thing on our older Q that can cause a rough idle are clogged injectors.  Even the best fuel injector cleaners that you add to gas on the market today can only be so effective in cleaning.  Generally, these products should be considered products to keep injectors clean than to clean dirty injectors.

Basically everything on the market now is no good except for BG 44k.  You can get it at , I have also bought it on E-bay as well.  I've tried even the best off the shelf things, and nothing else compares.  You will pay the price (about $20 for a can), but you will waste more money by using all those other things.

So, how do you clean dirty injectors.  The 90-93 Q45 are especially prone to clogging, due to the pintle design.  The 94+ do not have the pintle design.  In the picture below, the 90-93 injectors most resemble the injector on the left.  There is a single head and sprayer and this can get varnish particles on this causing the fuel atomization to be as good, meaning the burn will not be as complete.  The 94+ injectors are most like the ones on the left.  There are 2 little holes that spray the fuel.  Apparently this design does not suffer the same kind of cleanliness problems.


What a pressurized rail flush does is bypasses the stock fuel system all together during the operation.  The technician will hook up a canister looking thing to the car, and what this does is forces a special injector cleaning solvent through the injectors, effectively cleaning the injectors as well as the intake valves.

The key is to a proper injector flush is to step up the pressure above what the injector ever sees.  Generally, good practice is to have the technician to start the flow at the idle fuel pressure (34 PSI), and then slowly work up to 50-52 PSI for the final minutes.  The flush process takes about 15 minutes.  

After they do the flush, they will add some additive (like BG 44k) to the gas tank to help break up the remaining particles.

You should see increased fuel mileage, smoother idle, and lower emissions.

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