Got my spanner from John Speake on thursday (many thanks John).
Done the tests, and had two faults.. high/low battery voltage.. fault code 1111...possibly dirty connector because all the probed points are coming back with 11.5 - 12 volts and idle control valve 1122. have sprayed into pipe with wd40 but fault is still there, will have to strip and clean it properly...
Did the knock sensor test without having a rolling road.. Can be a bit hair raising (if i had hair) keeping the throttle wide open till the 10,000 cycles have passed ( but fun all the same) 05.30 this morning. so no police on the road.. they were all heading home for the shift changover. Did the test and 0 knocks were shown. so either car is very sound or the spanner is not working. But anyhow it gave it a pass so yahoo... Will try it on algies bag of bolts (only kidding buddy ) to see if it shows up any knocks on his S4. wonder if it tests for vinyl.? No thats another story

 

Now a predicament- he just bought a spanner at £360, if he connects it up to my car,and it starts flashing- do I thank him or kick him?
But seriously- should he be running the knock test at 3000 RPM or starting from idle and getting up to 3000 RPM for the knock test -anyone know??

 

Hi
If there are no stored knock sensor or Hall sensor fault codes, then it's unlikely there woulkd be any knocks recorded on a test drive.

No special technique required for the test drive. Just use lots of right foot, around max torque and at high rpm.

If there are fault codes of this type recorded, then the ignition will have been retarded, and so you're uinlikely to records knocks either ?

Confusing, eh ?

If an engine does record knocks even when a fault code as above is shown, then it has a SERIOUS problem !

I know of one instance of this. A guy thought there was a problem with his auto 'box. When near the red line it would "hang" for ages until it changed up gear.

On investigation it was found that yes, it did record knocks near the red line, this was retarding the igntion, causing the hang up. When the engine was stripped, it was found that it had a small end /piston problem.

 

Ah thanks john.. Reading the manuals i thought that it was less than 50 was a pass. so i was expecting to see some knocks recorded. As i have found out since getting the spanner it is not a black and white issue when dealing with these diagnostics. You have to read between the lines and some parallel thinking is neaded to narrow down the faults, because one component that is not working can be caused by something else in its path that has not given it the proper signal, triggering it to allow it to operate. ..................cheers...Jim

 

Hi Jim,
You are correct. A diagnostic tester is just another tool. The fault codes that are stored by the various ECUs are a snapshot of how the ECU "sees" the inputs it is receiving. This obviously has its limitations.

Having said that, you are much better off using a diagnostic tester than being without it !

Regards

 

Jim hooked up the spanner to my 88 S4 and it came up no faults,happy, happy , happy and to top it all off, the only 928 ever that his spanner has scanned as perfect
Thanks Jim-but don't I get a trophy?

 

Well the spanners diagnosis points to the throttle position switch as being the root of the trouble so i have ordered one from the local porsche dealer. £60 inc vat,, Will do the strip down of the intack system next week after we have had our playtime at the drag strip at crail on Sunday. Dont think the dodgy pos switch should affect the running up there.

 

I had also heard that the magic number for a good result from the knock test was 50 in 10,000. Anyone know for sure?

 

Hi Cameron,

Less than 50 in 10,000 firings is OK, 50 or more is a fail !

There has to be something pretty seriously wrong with an engine to get 50, because either a fully functioning knock system will stop the knock. Alternatively if there is a registered fault code with knock sensor or Hall sensor then the ignition would be retarded, and this should also stop the knock...

 

we have had our day out at crail drag strip, and all did not go well, for me that is. Algie was the champion on the day ( although i will deny this in mixed company) Hail Algie
Now for the possible causes,(not excuses.....Hounestly) Does the failure of the throttle position switch cause the timing to be retanded (6 degrees rings a bell).. I was finding that although i was getting a good start, that at the changeover point 2nd - third.. that the car was getting bogged down. Or is it that the valve on the modulator neads to be turned up a couple of turns to firm up the change.. Who knows.. This post is now closed from any gloating replies from Algie...Any additions will have to be made via another topic

 

Faulty throttle closed switch does not retard ignition - no excuses !

Only knock sensor or Hall sensor faults will retard ignition....

 

John.................................................................... ........................................................................ ........................................................................ .........................................................You should have sent me a pm to say that...You have blown it for me now.... never mind.. will have to think up another excuse now.. I suppose the list is endless though, so will try quoting from the manual....Cheers.................................Jim

 

........... you didn't mention that sudden, short lived 40mph head wind that sprang up for your run, did you ? :-)

Regards

 

Your right john.. there was mention of the right hand side of the track being affected by wind, and it was very gusty on Sunday , so that must be it. Thanks for reminding me.. cheers.....Jim