Fuel Injector Troubleshooting
As intimidating as it looks, the injection system is relatively simple to understand and you can do a few simple things to diagnose the problem.
1) Have a mechanic's stetoscope, and check each injectors individually. If one make a significantly different tapping noise you may have a pointer to your next step (see below, # 3 and 4))
2) You can also disconnect them one at the time. As long as you notice a change in engine behavior after disconnecting, you can skip to the next injector.
If you suspect any one injector to be faulty after these two tests, and before going to the next steps, you should give your Shark an extra dose of Chevron Techron and drive the car for a few days..(A full dose in half a tank did marvel once in my wife's BMW, without having to take anything apart)
3) If you decide you want to check some of the injectors a little closer, first get yourself the set of new O-rings (PN # 928 110 904 00 for a MY '87) You should NOT reuse an old O-ring, as most of the rubber parts under the hood are brittle after so many years and the last thing you want is a fuel leak while idling in traffic!
Handle the injectors very carefully as the nozzle is small and very fragile. Just in case, the PN for the MY '87 injectors is 928 606 119 02
4) with the whole rail out and the injectors mounted on it, you can do a simple leak test by activating the fuel pump (but without CRANKING the engine!!) and check if any of the injector leaks more than one small drop after about two minutes,. Use a soft clean light color cloth as protection for your injectors and to observe eventual leaks more easily.
'87 S4 Auto Nougatbraun Metallic/ Tan
928 Tips Home Greg's Home