[Gmecm] Help with unusual BLM's

Wed Mar 29 00:18:33 UTC 2006

Your misfire problem will cause low block learn
numbers. Less than 128 the ecm is subrtracting fuel
more than 128 it is adding fuel.

Just because the cap rotor, wires etc. is all new does
not necessarly mean it is good, what is the spark plug
gap at every plug, how many kv is the coil able to
produce, what is available at the wires. Invest in an
adjustable spark tester, one that is marked in kv, and
check each wire.  Set it to about 20,000 connect it to
one wire, start the engine, make sure the spark is
jumping the gap of the tester and not somewhere else,
shut the engine off and move the tester to the next
cylinder and repeat the process. also check the spark
plug gaps, maybee one got smashed shut, or to .010
when it should be .035, if one is .010 less than the
rest it will idle like a top but under a load at light
throttle it will misfire like crazy. especially a
small 4 cylinder

Dustin Lof

--- ahuxtable at sola.com.au wrote:

> Thanks for that Gene (and Steve - See further down)
> 
> As for your problem Gene, that was some of the first
> things I checked on
> this engine because oddly enough, it has a misfire
> problem.
> 
> I changed all plugs, leads, Cap, Button ignition
> module and ECM and it
> still does it.  It's not all the time, generally
> when hot and I rev over
> 4k RPM.  It sorta sounds as if I'm hitting rev limit
> but I'm not.
> 
> Still trying to find the cause of that one (which is
> also partly why I
> hooked up the lappy)
> 
> Steve, I get it now.  The BLM's being low is not
> that it's physically
> rich at that point, moreso that it is removing fuel
> because it 'was'.
> Makes so much more sense now that fuel is getting in
> somewhere else (As
> Dave mentioned). Will have to play some more.
> 
> Thanks for your help guys!
> 
> Andrew
> 
> -----Original Message-----
> From: gmecm-bounces at diy-efi.org
> [mailto:gmecm-bounces at diy-efi.org] On
> Behalf Of Randy & Gene
> Sent: Tuesday, 28 March 2006 11:10 AM
> To: gmecm at diy-efi.org
> Subject: Re: [Gmecm] Help with unusual BLM's
> 
>      Hi Andrew, today I solved a 3 year mystery as
> to why my 1993
> Pontiac
> Sunbird with a 3.1 V6 did exactly what your engine
> is doing. I had taken
> it
> to a dealer and Mr. Goodwrench charged me close to
> $1300 Cdn and
> couldn't
> fix the problem in 13 hours. I took it to another
> fellow who had worked
> for
> GM and he changed the upper and lower manifold
> gaskets citing there was
> a
> vacuum leak..$500...and another emissions shop
> charged me close to $200
> for
> telling me it had a vacuum leak near the back of the
> engine because when
> he
> sprayed a liquid in that area the engine sped up a
> bit......this car has
> a
> full body kit installed otherwise I would have towed
> it to the wrecking
> yard...anyway...I bought a 1992 Sunbird with the
> same engine for
> $350....bought a manual and laptop from E Bay and
> proceeded to swap
> parts
> out...O2,EGR,TPS,MAP,ECU and even checked every mile
> of cable harness
> for
> resistance...everything including injectors were
> swapped, throttle
> body.........nothing helped...then I decided to
> start over with
> basics....a
> simple compression test was first.....pulled all of
> the spark plug boots
> first then took out the 3 front plugs and number one
> from the
> back....number
> 3 was missing....or at least half of it was...part
> stuck in the boot and
> the
> other in the head......compression was good on all
> and when I supplied a
> plug from my parts car the 3.1 lit up like it was
> new..........you can't
> imagine my joy........the only code I ever got was a
> 45....rich O2...it
> had
> been replaced...a broken plug........make sure your
> basic stuff is in
> order
> first and good luck.....Gene
> 
> ----- Original Message ----- 
> From: <ahuxtable at sola.com.au>
> To: <gmecm at diy-efi.org>
> Sent: Sunday, March 26, 2006 8:04 PM
> Subject: [Gmecm] Help with unusual BLM's
> 
> 
> Hi all.  I've been trying to work out why for some
> reason my car has
> been running rich.  I just always assumed that it
> was the O2 sensor
> playing up - Until yesterday that is...
> 
> I logged some data and the highest BLM I saw was
> 120.  Most being around
> 115 so my engine is running fairly rich. So, the
> computer thinks that
> it's running rich and it actually is = not O2
> sensor.  Next I thought it
> might be the CTS or MAT sensors but logging them,
> it's all normal.  CTS
> reports running temp of ~85DegC (184DegF) and MAT is
> reading as expected
> too.
> 
> What else could be forcing the engine to run rich?
> 
> Thanks
> Andrew
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