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-   -   What is this noise....??? (http://forums.pelicanparts.com/porsche-928-technical-forum/785904-what-noise.html)

Yellowb1rd 12-07-2013 11:30 AM

What is this noise....???
 
Fellas,

I need a quick diagnosis on my 89 here. I'm noticing this horrible/dieseling knocking noise, but nothing mechanical has been changed on the car at this point (other than injectors)...

Car ran perfect two weeks ago, but I've changed out the injectors (to prepare for the installation of a supercharger) recently. This step in the process was to fire up the motor check for fuel leaks of any kind (before installing SC), of which there aren't BUT this noise is driving me bananas. The only other change I have made at this point is the installation of the shark tuner chip set in each computer. Timing belt was changed a couple of years ago BTW.

Is this:

1. Piston's colliding with valves (i have no idea how this is even remotely possible since the car ran perfectly before I started working on it)

2. Pre-ignition/detonation (from improper timing. Changed out the LH and EZK chipsets with the tunable sharktuner chipsets) THIS SEEMS TO BE THE MOST PLAUSIBLE

3. Something metallic got sucked into the maf (highly unlikely-there is a screen on it) or something metallic fell into one of the fuel injector ports during the changeout (also highly unlikely, as the holes are small, and I ran a magnet through each port as a precation)

4. Other????

I've also re-installed the factory chip back into the EZK just to see if I can rule out ignition issues, and now it wont even start. Upon further investigation, it's not getting spark t the plugs. What have I done to my once perfectly running car?!

Mrmerlin 12-07-2013 12:41 PM

did you blow out the injectors with air prior to removing them? sometimes sand and other debris will fall into the injector holes

Yellowb1rd 12-07-2013 01:23 PM

I did not use any air. I was very careful to keep those holes plugged, however, while working on the car.

Yellowb1rd 12-07-2013 01:28 PM

Is it possible if the shark tuner chipset (for the EZK, namely) default values were so far off, that it changed the timing radically enough to cause a collision between valves and pistons? That is the only that any sort of collision would be remotely possible, since nothing mechanical was changed (and since the injectors are controlled by the LH, I don't really consider the injectors a mechanical change).

So, now I have two issues here to resolve. One, what could cause the noise I'm hearing, and two, why the car will now no longer start. Any way to test the EZK to make sure it's not blown? Since the EZK controls ignition, I'm focusing on that one for the time being.

lfausty 12-07-2013 02:53 PM

could try unplugging the fuel inj relay plugging back in/wiggle , swap, or a new one.

Mrmerlin 12-07-2013 05:00 PM

its common practice to use compressed air to blow out the top of the intake around the injectors where they seal to remove any loose sand

lowpassat 12-07-2013 08:59 PM

I think #2 is most likely. Do you hear it while driving under load (accelerating)?


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