4.3 running rich, no codes:
burntkat
got an 89 S10 Blazer, Vin Z, TBI, 4.3, 700R4:
new TPS, IAC, cleaned and rebuilt TBI, new FPR <to include spring>, CTS, MAF
<or is it MAP?> sensor, O2 sensor. Basically everything but the knock
sensor.
I'm running rich as evidenced by the soot-coated exhaust pipe and the smell
of gas at the pipe.
Computer throws no codes, I have logged data from WinALDL but am not sure
how to interpret it.
Am installing an Air/fuel gauge, but haven't had time to do more than
physically mount it due to the weather and having my garage full of crap
<just moved into a house>.
No info on fuel pressure. I would assume a dying fuel pump would put out
less fuel and therefore make the engine run lean.
Air filter is a K&N, and is cleaned regularly.
Checked base spark timing as per the manual- disconnect the ESC wire, set
timing to 4deg BTDC, reconnect. When I check the timing during operation, it
retards to abotu 10deg BTDC. So apparently there is something being told to
the ECU to make it retard. I can hear no spark knock or other mechanical
noises other than a tapping exhaust pipe or something of the sort at idle,
which goes away with application of throttle. Again, haven't had time to
investigate.
I'm getting 14MPG, and I bet if I track this down I can get 3 more. She's
running REALLY retarded <!?> and really rich...
ideas?
Doc- you said something about the HB being off a tad- how would one check
for that? I know normally you can pull a plug, put a dowel in the motor, and
turn it over by hand till you're at TDC and compare the HB's position re:
the timing marks. However, this basically being a smallblock- the spark
plugs enter the head at an angle, so that would be a ballpark operation at
best.
"Doc"
"burntkat" <no...@nowhere.com> wrote in message
news:oN8zc.40868$2o2.2...@twister.southeast.rr.com...
> Ping Doc, et al:
<Huge Snip>
Kat,
Your spark retard is what's causing it to run rich. When you plug in the
EST it should ADVANCE from base timing, not retard. Generally speaking, if
base is set at 4*BTDC, you should be seeing 12-16* BTDC with EST plugged in.
Pull the KS and have it tested at AZ. If the ESC module isn't getting s
signal from the KS, it defaults to max spark retard and could be causing
your problems. Wire could also be melted to the exhaust manifold which is
common.
Doc
"Doc"
"burntkat" <no...@nowhere.com> wrote in message
news:oN8zc.40868$2o2.2...@twister.southeast.rr.com...
> Ping Doc, et al:
<another snippet>
I forgot, to check the HB, pull a plug, stick a finger in the plug hole and
have someone hand turn the engine till you get pressure. This should get
you close enough to know if the HB is off or not.
Doc
burntkat
""Doc"" <no...@nope.com> wrote in message
news:luSdnU68lsj...@adelphia.com...
> Your spark retard is what's causing it to run rich. When you plug in the
> EST it should ADVANCE from base timing, not retard. Generally speaking,
if
> base is set at 4*BTDC, you should be seeing 12-16* BTDC with EST plugged
in.
I may be off. I know I set it at 4deg BTDC, and after plugging the ESC back
together I note approximately 10deg BTDC. We seem to be saying the same
thing?!?
> Pull the KS and have it tested at AZ. If the ESC module isn't getting s
> signal from the KS, it defaults to max spark retard and could be causing
> your problems. Wire could also be melted to the exhaust manifold which is
> common.
Hadn't thought of these. Will check tomorrow, assuming it doesn't rain or I
manage to get the crap in the garage cleared out.
Just toko the truck on a quick beer run, and I believe the rattling <perhaps
a exhaust pipe rattling against a crossmember> is throughout the powerband
not just at idle. Perhaps this is being registered by the knock sensor as
knock?
Thanks for getting back to me on this.
Neil Nelson
"burntkat" <no...@nowhere.com> wrote:
> Ping Doc, et al:
>
> got an 89 S10 Blazer, Vin Z, TBI, 4.3, 700R4:
>
> new TPS, IAC, cleaned and rebuilt TBI, new FPR <to include spring>, CTS, MAF
> <or is it MAP?> sensor, O2 sensor. Basically everything but the knock
> sensor.
MAP, GM trucks didn't use a MAF sensor until later years.
> I'm running rich as evidenced by the soot-coated exhaust pipe and the smell
> of gas at the pipe.
Tailpipe color is very misleading, pull a few sparkplugs and
check them for color.
> Computer throws no codes, I have logged data from WinALDL but am not sure
> how to interpret it.
Maybe post the most important ones like the readings from the
CTS, O2, MAP, TPS and RPM.
> Am installing an Air/fuel gauge, but haven't had time to do more than
> physically mount it due to the weather and having my garage full of crap
> <just moved into a house>.
>
> No info on fuel pressure. I would assume a dying fuel pump would put out
> less fuel and therefore make the engine run lean.
And a pinched/restricted fuel return line will put in more.
You can't skip parts of the diagnosis and/or assume.
> Air filter is a K&N, and is cleaned regularly.
>
> Checked base spark timing as per the manual- disconnect the ESC wire,
You should be disconnecting the -EST- wire not the ESC wire, they
are two entirely different things and serve different functions
WRT ignition timing.
> set
> timing to 4deg BTDC, reconnect. When I check the timing during operation, it
> retards to abotu 10deg BTDC.
The timing moving from 4º BTDC to 10º BTDC is -ADVANCING- not
retarding.
> So apparently there is something being told to
> the ECU to make it retard. I can hear no spark knock or other mechanical
> noises other than a tapping exhaust pipe or something of the sort at idle,
> which goes away with application of throttle. Again, haven't had time to
> investigate.
Investigate, the knock sensor may be hearing whatever it is
that's banging/rattling and retard the timing while you're
driving killing your fuel economy.
>
> I'm getting 14MPG, and I bet if I track this down I can get 3 more. She's
> running REALLY retarded <!?> and really rich...
Actually, you haven't really posted any evidence of either yet.
> ideas?
>
> Doc- you said something about the HB being off a tad- how would one check
> for that? I know normally you can pull a plug, put a dowel in the motor, and
> turn it over by hand till you're at TDC and compare the HB's position re:
> the timing marks. However, this basically being a smallblock- the spark
> plugs enter the head at an angle, so that would be a ballpark operation at
> best.
Make a positive piston stop by gutting out an old sparkplug,
tapping the inside bore and threading in a long enough bolt or
stud, install the piston stop in #1 sparkplug hole, hand turn the
engine one direction until the piston stops against the piston
stop, mark the harmonic balancer, hand turn the engine the
opposite direction until the piston stops against the piston
stop, mark the harmonic balancer, your factory timing mark
-should- lie exactly in between the two marks you made, if not,
the balancer has slipped.
One other thing to check is the pole piece inside the
distributor, you're looking for cracks in the magnet radiating
away from the rivets that hold the laminations of the pole piece
together. if you see any cracks, procure a suitable replacement,
if that replacement is a remanufactured distributor, examine -it-
closely to make certain you're not getting one that also has a
cracked pole piece.
"Doc"
> inline...
>
>
> ""Doc"" <no...@nope.com> wrote in message
> news:luSdnU68lsj...@adelphia.com...
>
> > Your spark retard is what's causing it to run rich. When you plug in
the
> > EST it should ADVANCE from base timing, not retard. Generally speaking,
> if
> > base is set at 4*BTDC, you should be seeing 12-16* BTDC with EST plugged
> in.
>
> I may be off. I know I set it at 4deg BTDC, and after plugging the ESC
back
> together I note approximately 10deg BTDC. We seem to be saying the same
> thing?!?
You said it was RETARDING to 10* BTDC; I assumed you made a typo and meant
retarding to 10* ATDC. It is in fact ADVANCING to 10* BTDC then?
Doc
burntkat
Hmm-- now I'm wondering if mabe I didn't pull a dumbass and time it to the
wrong side.... <ATDC instead of BTDC>.. though I would think it would have
no power. Engine pulls strong.
""Doc"" <no...@nope.com> wrote in message
news:ZPSdnfJV39f...@adelphia.com...
Brian Orion
---------------------------------------------------------------
I heard(but have not yet tried) that you can test a knock sensor by
rapping the area near the sensor with a wrench and watching the RPMs
drop (or not).Anybody familiar with this ?
Or you could watch the timing marks while rapping the case I suppose.