Tuning continued...

[Todd....!!]

Had the same thing happen with plugs, swapped em all out, miss, popping,
all gone....

When testing theplugs outside the engine, they all sparked just GREAT!

Go figure!!

I'll NEVER look past the plugs and wires again, when troubleshooting a
miss/backfire/popping out the exhaust.

ALSO found out that a lean condition can result in popping out the
exhaust as well!!

Any technical expertise as to why this occurs?

You'd THINK that if the a/f ratio was lean, REALLY lean, that
predetonation would occur, however, it seems that the opposite is
true...

And the popping actually occurs out the exhaust!!

Maybe the mixture was SO lean that the spark couldn't ingite the mixture
whilst it was in the chamber but COULD once it was in a lower pressure
environment outside the chamber in the exhaust system???

Just a thought...

Great discussion on troubleshootin/tunin...

Keep it up!

Learnin a lot... as always....

LATER!

Todd....

http://www.c-com.net/~atc347/toddlnk.htm

christer.medin at lennoxintl.com wrote:
> 
> Yeah, we were wondering if maybe the advance was too much, but it's fairly conservative - 36 degrees at 3000RPM.  Good info about the wires, if the plugs are ok, I guess we can just swap the stock wires back in and see if it makes a difference. Thanks.
> 
> Christer
> 
> ----------
> From:   MIME :n5xmt at bellsouth.net
> Sent:   Wednesday, June 16, 1999 12:39 PM
> To:     gmecm at efi332.eng.ohio-state.edu
> Subject:        Re: Tuning continued...
> 
> It could be the advance you have dialed in is too much for the engine at
> that particular RPM/load... What works on a dyno doesn't necessarily
> corrrelate to what works in the vehicle... varying load in the car from
> Trans, road conditions etc.
> Another point is the plug wires... Don't know how many times I had weird
> stumbling/miss problems on my Buick GN, change plugs, no change, check
> wires, all measure great (remember, the DMM uses between 1 and 9 volts for
> Ohms... Ignition blasts 20K plus depending on the type of ignition) and
> finally changed the wires just because... Stumble/miss disappeared.
> 
> Later,
> DAve