knock knock goes the jeep....

[digi]

Sounds similar to a problem I had, is it running a bit lean?

My fuel pump was dying, it was running a bit lean, and it would heat up
the plugs and ignite the fuel, tried the highest octane/zero advance/etc.

It may be worth a shot to check the fuel pressure, can't hurt and isnt a
hard thing to do.
- Brian

On Wed, 29 Dec 1999, John S. Gwynne 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
>