knock knock goes the jeep....

[David Cooley]

A couple possibilities:
Lean and No EGR.



At 02:53 PM 12/29/1999 -0500, you wrote:

>Hi All,
>
>Here's a problem that I'm working on....
>
>engine: '88 TPI 5.0L with Vortech SC (FMU and MSD boost retard) running
>'7730 with '92 axxc bin (nearly identical to anth etc..). This is in my
>Jeep with an NV4500 trans (5-speed manual 0.72 or-so over-drive, 4.10
>gears, 33" tires).
>
>problem:
>
>I'm was cruising on the highway in 5th and started up a moderate grade
>while following someone. As the person moves over, I
>down shift into 4th (about 6845 sec on the tps plot of
><ftp://jsgpc.mrcday.com/pub/knock/tps.jpg>), delay a few seconds till
>the road was clear and gave it some gas... heard it knock... I lifted then
>tried again around 6850 seconds... still no go. At about 6855 seconds,
>I shifted back into 5th. From about 6855 seconds and on, it was in 5th and
>now knocking. It didn't fully recover until about 6960 seconds.
>
>The spark advance is plotted in
><ftp://jsgpc.mrcday.com/pub/knock/sprkAdv.jpg>, and the rpm in
><ftp://jsgpc.mrcday.com/pub/knock/rpm.jpg>. As I went back into 5th at
>6855 seconds, the knock sensor has pulled out almost 20 deg of timing
>(the timing goes into retard and is also shown as such in MW1)
>BUT... it's still knocking. no real boost at this rpm and something
>that it would not otherwise do.
>
>I believe this has only happened three or four times now. Each on long
>trips and shifting down to fourth to pass.  Other than that, the car
>has been running fine. Accelerating from a stop or slower speed has
>not had any such problem.
>
>Other plots:
><ftp://jsgpc.mrcday.com/pub/knock/afr.jpg>
><ftp://jsgpc.mrcday.com/pub/knock/inj.jpg>
><ftp://jsgpc.mrcday.com/pub/knock/knock.jpg>
><ftp://jsgpc.mrcday.com/pub/knock/map.jpg>
>
>I don't see how it could knock with so little timing advance (more
>like none) at times past 6855 seconds and shifted back into fifth.  Is
>my interpretation of the data steam correct? bytes 39:40 of the ALDL
>stream (0x3128 and 0x3129 in the 7730 memory map) seem to be spark
>advance without ref and knock correction. bytes 41:42 (0x30bd and
>0x30be) are relative to the DRP and include knock correction.
>
>Any thoughts on what it is doing and how to fix it?
>
>john gwynne

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David Cooley N5XMT Internet: N5XMT at bellsouth.net
Packet: N5XMT at KQ4LO.#INT.NC.USA.NA T.A.P.R. Member #7068
We are Borg... Prepare to be assimilated!
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