ping

[CSH-HQ]

In my earlier mention of the heater fan rfi triggering a knock signal was 
well over 40 hours, and got .3 hr flat rate for that.  GM rep, and I had 
some words, over that one.
Grumpy




>I had an interesting time working on a friends Turbo Grand Prix.  It came to
>me with a rough idle so, slapped on the Diacom and found a consistent line
>of 7 degrees knock retard all the time, cool, a new one on me (just wait).
>No engine noises and all things are fairly new on this car (I put in a while
>ago; new injectors, some sensors and such), so I swap out the ECM with a
>known good one (that is easier than swapping the knock sensor) and still 7
>degrees all the time.  Swap out the knock sensor and still.  Pull out the
>(single) knock wire from both connector ends and ohm it out, good wire and
>not going to ground, even when shaking the engine by hand.  Check volts out
>of ECM, fine here.  Pull out wire and visually inspect its entire length,
>good again, check wire loom and no pinch or running near anything that could
>cause a false ?  Tired of this stuff I just grab some twisted pair/shielded
>cable and run a new wire in a new wire loom and in a different location and
>presto, 7 degree knock gone and been so for 8 months (also tested it still
>work by the usual thump test, and some higher boost, as we tuned up his chip
>for 100 octane).  I also took the braided shield of this wire and on one end
>(did not want to create a ground loop) secured it to a good ground, with
>other ground wires.
>
>(always up to a new challenge)
>Jeff Middaugh
>tystorm at email.msn.com
>
>
>> You need to watch the timing with some type of scan tool.  I would do this
>> before spending money on anything else.
>> Mark  By the way, I know why you would twist the wires.  I have just never
>> heard of a problem with rfi on the knock sensor circuit.  The ecm is set
>up
>> to look for specific frequency so I doubt rfi would trigger knock retard.
>> Mark
>> -----Original Message-----
>> From: David Mulvey <kd6bzn at QNET.COM>
>> To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
>> Date: Monday, August 23, 1999 11:36 PM
>> Subject: Re: ping
>>
>>
>>
>>
>> > It sounds to me like the knock sensor is NOT working and/or egr problem.
>> The
>> > best way to check the knock sensor is to take a plunger handle, and drop
>> it
>> > with it's own weight only onto the block near the knock sensor.  Watch
>the
>> > timing, (Scan tool) and make sure the ecm is pulling some timing out.  I
>> > have never heard of twisting the wires.  I have ALL the tech bulletins
>on
>> > the L98.  I have tuned the knock sensor a bit by using a bit of teflon
>> tape
>>
>> The twisting of the wires is just a simple way of keeping some low
>frequency
>> RF from resonating on a stran of wire.  As long as the
>> wire twists the RF has only very small untwisted sections to resonate.
>>
>> I checked the EGR valve and the EGR solenoid and the voltage to the
>> solenoid.  All Ok, a good vaccuum to the egr valve caused the
>> motor to idle down..  I cleaned out the EGR solenoid gave it a test on a
>12
>> volt power supply. So EGR I think it fine.
>>
>> I do have one old injector on the side of the engine that doesn't have the
>> O2 sensor. Could be a suspect.  I have 3 old injectors on
>> the O2 sensor side, and do not get any mixture errors.
>>
>> I was wondering about the Knock sensor too.  I do get error 43 which I
>think
>> is the code showing that the knock count exceeded it's
>> limits. An audible ping/knock is also heard at this time.  I guess I was
>> wondering if the knock sensor maybe was only working a little
>> not detecting the all of the knocks then causing the computer not to
>adjust
>> properly then setting off the MAF voltage too high and/or
>> too low..  Kinda getting complicated at this point.
>>
>> I still need to check the ground to the MAF sensor.
>> I still need to give the knock sensor wires a couple of twists.
>> I want to replace the 4 old injectors I have, (short on funds at the
>moment)
>> AutoZone has injectors for $35 each.
>> Am I buying crap or are these things workable?
>> AutoZone also has MAF sensors for $139,
>> $80 core charge. (got one the other day, same 'ping')
>> practically everything else is new except for the ESC module.
>> I figured the ESC is probably working since
>> I do have a car that runs.. Good assumtion?
>> I need to see if the knock sensor is working using the plunger stick test.
>> I haven't gotten into changing ECM values yet.  Will not hesitate if
>nothing
>> else seems to work.
>> "PE vs. RPM table"  =- What's 'PE'?
>>
>> For the Knock sensor test would I notice a timing change using the plunger
>> handle and a timing light? I got one of those..
>>
>>
>> end
>> ----
>> David Mulvey KD6BZN
>> Lancaster, CA
>> (661) 723-0352
>>
>>
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