Engine misses on stone cold start-up

RF_Burns

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
5,148
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Ontario Canada
So I've been trying to figure out an engine miss from stone cold start-up for a long time now... it's an on and off project. Once the engine is
warmed a bit and rev'ed to clear it out, its good for the rest of the day, even after sitting for hours it will then start and run fine.

So I start the engine, it starts right up but has a definite miss. When put into gear and rev'ed to move it, you can definitely feel it missing.
However give it a minute, then rev it up to 1500rpm, it will run rough.. blow a bit of black smoke then smooth out and run fine for the rest of the
day.

I have a cold intake manifold (cross-over blocked) so I thought it was fuel condensing on the runners. Also the pre-heat cowling from the exhaust
manifold is long gone so it doesn't get pre-heated air. When I rev'ed it, the increased air flow picks up the condensed fuel and makes a rich mixture
for a few seconds then its cleared out and all is good. I have Throttle body EFI (originally Howell now EBL with Rochester TB) so adjusting the
startup mixture is easy. Maybe fuel-drop-out is normal with a cold manifold. When I start it and pull it out of the shop, there is a heavy gas
smell, so I can likely lean the choke setting even more.

What drives me nuts is the miss on one cylinder (I believe its only one). Over the years I have changed plugs and wires (DickP's wires and his
recommendation of two different spark plugs). New coil and pickup of the correct polarity from DickP. New ignition module. BTW it did this running
on OEM HEI and also now on Spark Control from the EBL.

I've tried starting it and let it run for 30 seconds or so, then pulled the plugs to see if I could troubleshoot which plug the miss was on. I could
not see much difference between them.

I tried wrapping little copper wire out of each of the sparkplug wires at the distributor. Using them I could short the spark for each cylinder and
see if I could determine which one was missing. I could invoke a miss on every cylinder, even while it was missing. So this lead me to believe it
must be a random miss and not one particular cylinder.

It never backfires. However, even warm when rev'ed up to 1500-2000 rpm it runs a bit rough... not smooth like I would expect. It was rebuilt by
DickP back in 2009 and I've asked him about it a couple of times... he though it was fine. I didn't specifically ask to have it balanced during the
rebuild... I didn't know of such a thing at the time.

Anyway, does anyone have any ideas on my "missing" problem? I've lived with it for years but it just bugs me. I was thinking of putting a pickup
coil on the HV output of the coil so I could look at it on my oscilloscope, but with HEI, there is no way to get to that. Maybe scoping the Tach
output would give me some indication if an Ignition system problem...?

What say ye?

Thanks

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
> So I've been trying to figure out an engine miss from stone cold start-up for a long time now... it's an on and off project. Once the engine is
> warmed a bit and rev'ed to clear it out, its good for the rest of the day, even after sitting for hours it will then start and run fine.
>
> So I start the engine, it starts right up but has a definite miss. When put into gear and rev'ed to move it, you can definitely feel it missing.
> However give it a minute, then rev it up to 1500rpm, it will run rough.. blow a bit of black smoke then smooth out and run fine for the rest of the
> day.
>
> I have a cold intake manifold (cross-over blocked) so I thought it was fuel condensing on the runners. Also the pre-heat cowling from the exhaust
> manifold is long gone so it doesn't get pre-heated air. When I rev'ed it, the increased air flow picks up the condensed fuel and makes a rich
> mixture for a few seconds then its cleared out and all is good. I have Throttle body EFI (originally Howell now EBL with Rochester TB) so adjusting
> the startup mixture is easy. Maybe fuel-drop-out is normal with a cold manifold. When I start it and pull it out of the shop, there is a heavy gas
> smell, so I can likely lean the choke setting even more.
>
> What drives me nuts is the miss on one cylinder (I believe its only one). Over the years I have changed plugs and wires (DickP's wires and his
> recommendation of two different spark plugs). New coil and pickup of the correct polarity from DickP. New ignition module. BTW it did this
> running on OEM HEI and also now on Spark Control from the EBL.
>
> I've tried starting it and let it run for 30 seconds or so, then pulled the plugs to see if I could troubleshoot which plug the miss was on. I
> could not see much difference between them.
>
> I tried wrapping little copper wire out of each of the sparkplug wires at the distributor. Using them I could short the spark for each cylinder
> and see if I could determine which one was missing. I could invoke a miss on every cylinder, even while it was missing. So this lead me to believe
> it must be a random miss and not one particular cylinder.
>
> It never backfires. However, even warm when rev'ed up to 1500-2000 rpm it runs a bit rough... not smooth like I would expect. It was rebuilt by
> DickP back in 2009 and I've asked him about it a couple of times... he though it was fine. I didn't specifically ask to have it balanced during the
> rebuild... I didn't know of such a thing at the time.
>
> Anyway, does anyone have any ideas on my "missing" problem? I've lived with it for years but it just bugs me. I was thinking of putting a pickup
> coil on the HV output of the coil so I could look at it on my oscilloscope, but with HEI, there is no way to get to that. Maybe scoping the Tach
> output would give me some indication if an Ignition system problem...?
>
> What say ye?
>
> Thanks

Bruce,

I just had a new GMC owner on his maiden voyage home to CA from MI stop by here a couple of weeks ago with a similar "miss". I chased ignition
replacing coils, modules, spark plugs to no avail. I was certain it was ignition as that is the way it behaved. This was with just a Howell system. I
put my EBL on thinking that might clear up the issue but still persisted.

For some reason, I got the bright idea to watch the injector spray pattern while the miss was occurring. The right side was easiest to see so started
there but everything looked good. I then watched the other one. Every time we felt a miss, that injector would not spray for one or two cycles. Felt
just like an ignition miss. Going back and studying the log, I could see a momentary lean condition followed by rich as the EBL compensated for the
lean cycles. I happened to have an extra set of injectors of the same type that we exchanged and the coach ran great after that.

For what it is worth...
--
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO
 
1 What’s your plug gap?
2 sounds like your choke pull off is mal adjusted. This is a critical adjustment and more important than actual choke setting during first couple
minutes of cold operation. Try manually opening the choke an 1/8” at startup. If RPM increases you have not enough pull off. The lack of
crossover heat and no AutoThermAC have created a perfect storm of bad. When setup right they start and run and transition beautifully.
3 your idle mixture may be set wrong especially on the needle feeding the wet cylinder. With coolant at 195 set both sides for max idle speed. Then
lean to just at the edge point where RPM starts to want to drop but does not. Turn in each screw for 25 RPM drop on one and the other for a total of
50 RPM drop. This is the lean drop setting which may help with your problem.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Randy, are you using a timing light to “see” the spray? Or can you just look at the injector in use and see when it fails?

> > So I've been trying to figure out an engine miss from stone cold start-up for a long time now... it's an on and off project. Once the engine
> > is warmed a bit and rev'ed to clear it out, its good for the rest of the day, even after sitting for hours it will then start and run fine.
> >
> > So I start the engine, it starts right up but has a definite miss. When put into gear and rev'ed to move it, you can definitely feel it
> > missing. However give it a minute, then rev it up to 1500rpm, it will run rough.. blow a bit of black smoke then smooth out and run fine for the
> > rest of the day.
> >
> > I have a cold intake manifold (cross-over blocked) so I thought it was fuel condensing on the runners. Also the pre-heat cowling from the
> > exhaust manifold is long gone so it doesn't get pre-heated air. When I rev'ed it, the increased air flow picks up the condensed fuel and makes a
> > rich mixture for a few seconds then its cleared out and all is good. I have Throttle body EFI (originally Howell now EBL with Rochester TB) so
> > adjusting the startup mixture is easy. Maybe fuel-drop-out is normal with a cold manifold. When I start it and pull it out of the shop, there is
> > a heavy gas smell, so I can likely lean the choke setting even more.
> >
> > What drives me nuts is the miss on one cylinder (I believe its only one). Over the years I have changed plugs and wires (DickP's wires and
> > his recommendation of two different spark plugs). New coil and pickup of the correct polarity from DickP. New ignition module. BTW it did this
> > running on OEM HEI and also now on Spark Control from the EBL.
> >
> > I've tried starting it and let it run for 30 seconds or so, then pulled the plugs to see if I could troubleshoot which plug the miss was on.
> > I could not see much difference between them.
> >
> > I tried wrapping little copper wire out of each of the sparkplug wires at the distributor. Using them I could short the spark for each
> > cylinder and see if I could determine which one was missing. I could invoke a miss on every cylinder, even while it was missing. So this lead me
> > to believe it must be a random miss and not one particular cylinder.
> >
> > It never backfires. However, even warm when rev'ed up to 1500-2000 rpm it runs a bit rough... not smooth like I would expect. It was rebuilt
> > by DickP back in 2009 and I've asked him about it a couple of times... he though it was fine. I didn't specifically ask to have it balanced
> > during the rebuild... I didn't know of such a thing at the time.
> >
> > Anyway, does anyone have any ideas on my "missing" problem? I've lived with it for years but it just bugs me. I was thinking of putting a
> > pickup coil on the HV output of the coil so I could look at it on my oscilloscope, but with HEI, there is no way to get to that. Maybe scoping
> > the Tach output would give me some indication if an Ignition system problem...?
> >
> > What say ye?
> >
> > Thanks
>
> Bruce,
>
> I just had a new GMC owner on his maiden voyage home to CA from MI stop by here a couple of weeks ago with a similar "miss". I chased ignition
> replacing coils, modules, spark plugs to no avail. I was certain it was ignition as that is the way it behaved. This was with just a Howell system.
> I put my EBL on thinking that might clear up the issue but still persisted.
>
> For some reason, I got the bright idea to watch the injector spray pattern while the miss was occurring. The right side was easiest to see so
> started there but everything looked good. I then watched the other one. Every time we felt a miss, that injector would not spray for one or two
> cycles. Felt just like an ignition miss. Going back and studying the log, I could see a momentary lean condition followed by rich as the EBL
> compensated for the lean cycles. I happened to have an extra set of injectors of the same type that we exchanged and the coach ran great after that.
>
>
> For what it is worth...

--
C. Boyd
76 Crestmont
East Tennessee
 
Hi Randy.
I'll take a look at the injectors, but I had this problem with the Howell Holley before I installed the Rochester TB. Still could be the issue since
the Rochester had one bad injector when I got it. I replaced them with two new injectors before installing it. New doesn't always mean works
perfectly thought.

On my choke settings, the Choke Decay Multiplier %... do you know how that parameter works? I'm assuming that every so many seconds after start-up, it
decays the choke by this percentage. Would you know what that timer period is? or am I wrong?

Hi John. I have fuel injection, however there are "choke" settings to adjust the AFR dependent on coolant temperature and a decay function to lean
off the choke.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Bruce,

You have run all the diagnostics that I would run. I like your trick for shorting plugs. It is particularly good as an open plug can damage HEI.

So, what you have comes down to a power imbalance most likely caused by a mixture distribution problem. Your shorting individual plugs sure says that
this in not an ignition issue. We can skip that.

While I have used the timing light to see the injector spray trick, I also have to allow that the majority of times I have had to diagnose this, I
have had access to serious diagnostic gear. I don't now and am stretching my brain to come up with alternatives. Unfortunately, the O2 sensor is
probably not hot enough to work when this is happening. I think if you can watch that come on-line, it might tell you which bank is rich/lean if you
have two.

My first vote would still be a mixture distribution issue. The first of these would be a problematic injector. They do have two common mode failures
- too much fuel and too little fuel. Either could do this and even if you look at the driver pulse width, that will not tell you about mechanical
issues. This is where the timing light trick works. If you have access to a "dial advance" unit, that can help, but you can also pick different plug
wires to look at the injectors in different parts of the cycle. I hope something shows up there because my next guess is a crack in the intake
manifold.

Yes, a leak in the intake could do this exactly. With the cold manifold mod, it is less likely but still possible. That would allow the mixture of
one set to go lean until the engine heat closes the leak/crack. I don't know how I would make a solid diagnosis of this as it could be a crack in the
manifold casting or a bad fit to the cylinder head.

One thing about writing like this is that the brain is always running a parallel process while the fingers are working and that just brought up
another possible issue that is related to some, but not all of the above. If you have an injector that leaks, the intelligence of the ECU could
compensate during running and as long as it is not too far out of bad, it would not even throw a code. But it could leak enough fuel into the
manifold after shut-down and before actual start-up to make one side or a single cylinder way rich at start up. The time that I saw this one, it made
warm restarts real bad.

Whatever, when you do find it, please tell us.

Stay Healthy

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
OK,
First time I heard of using the strobe light to freeze the action of spray.
One can learn a lot and also refresh the mind by reading these discussions.
Thank you all for asking and responding.😷

On Sun, May 31, 2020 at 9:07 AM Matt Colie via Gmclist <

> Bruce,
>
> You have run all the diagnostics that I would run. I like your trick for
> shorting plugs. It is particularly good as an open plug can damage HEI.
>
> So, what you have comes down to a power imbalance most likely caused by a
> mixture distribution problem. Your shorting individual plugs sure says that
> this in not an ignition issue. We can skip that.
>
> While I have used the timing light to see the injector spray trick, I also
> have to allow that the majority of times I have had to diagnose this, I
> have had access to serious diagnostic gear. I don't now and am stretching
> my brain to come up with alternatives. Unfortunately, the O2 sensor is
> probably not hot enough to work when this is happening. I think if you
> can watch that come on-line, it might tell you which bank is rich/lean if
> you
> have two.
>
> My first vote would still be a mixture distribution issue. The first of
> these would be a problematic injector. They do have two common mode
> failures
> - too much fuel and too little fuel. Either could do this and even if you
> look at the driver pulse width, that will not tell you about mechanical
> issues. This is where the timing light trick works. If you have access
> to a "dial advance" unit, that can help, but you can also pick different
> plug
> wires to look at the injectors in different parts of the cycle. I hope
> something shows up there because my next guess is a crack in the intake
> manifold.
>
> Yes, a leak in the intake could do this exactly. With the cold manifold
> mod, it is less likely but still possible. That would allow the mixture of
> one set to go lean until the engine heat closes the leak/crack. I don't
> know how I would make a solid diagnosis of this as it could be a crack in
> the
> manifold casting or a bad fit to the cylinder head.
>
> One thing about writing like this is that the brain is always running a
> parallel process while the fingers are working and that just brought up
> another possible issue that is related to some, but not all of the above.
> If you have an injector that leaks, the intelligence of the ECU could
> compensate during running and as long as it is not too far out of bad, it
> would not even throw a code. But it could leak enough fuel into the
> manifold after shut-down and before actual start-up to make one side or a
> single cylinder way rich at start up. The time that I saw this one, it made
> warm restarts real bad.
>
> Whatever, when you do find it, please tell us.
>
> Stay Healthy
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
> Randy, are you using a timing light to “see” the spray? Or can you just look at the injector in use and see when it fails?

Chuck,

I normally use a timing light because that "stops" the spray. However, in this case I just used a bright light behind the injector which illuminates
the spray quite well. I just used the flashlight function on my phone. Works great. The timing light is better if you have a leaking injector (too
much fuel) because you can better see the globs that normally occurs with a leaky injector. I have not seen an injector completely miss a cycle or two
before but certainly did in this case and felt just like an ignition miss.

--
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO
 
Bruce are you still chasing this? There are a couple things you could also look at or into.

Question.....what happens if you start it on dual battery and leave it that way for a little bit after, does it miss on both batteries?

Question....does it only do it cold, first start or just cold [meaning bellow 195, thermostat closed}...we need to figure out if your problem is in
open loop or closed loop.

Question.....do you have an isolater or a combiner?

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
> Hi Randy.
> I'll take a look at the injectors, but I had this problem with the Howell Holley before I installed the Rochester TB. Still could be the issue
> since the Rochester had one bad injector when I got it. I replaced them with two new injectors before installing it. New doesn't always mean works
> perfectly thought.
>
> On my choke settings, the Choke Decay Multiplier %... do you know how that parameter works? I'm assuming that every so many seconds after
> start-up, it decays the choke by this percentage. Would you know what that timer period is? or am I wrong?
>
> Hi John. I have fuel injection, however there are "choke" settings to adjust the AFR dependent on coolant temperature and a decay function to
> lean off the choke.

Could be an intermittent problem with wiring to the injectors? I just used a light behind the injectors that allowed me to see the spray pattern and
it was obvious when one missed a couple of cycles. I exchanged the injector connectors to verify that it was the injector and not the wiring. Because
you have changed the injectors, I would not think you would see the exact same symptoms if your problem is the injectors (unless there is a problem
with the wiring or the injector driver (have you tried a different ecu?))

Yes, it decays as you indicate. There is a parameter in scalars that controls the interval of the decay - set to 2 seconds by default. Have you tried
a bin that has not had changes made to the choke setting. In other words, I assume you have made changes to the default setting since you are looking
there so going back to defaults might tell a story. Quite frankly, I seldom have to make changes to choke setting because the default seem to always
work well. When I have changed, I have noticed that unless you make very large changes, the over running of the engine does not change that much.

Oh, and what Matt said. I agree with his analysis.

--
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO
 
I ran for awhile with ignition power connected to the ECM 12V BAT input and it gave me cold start issues due to the IAC not going to the park position
(which it is supposed to do on BAT once ignition is switched off).

Here is an excerpt from a 3rd Gen forum post....

"From RBob's EBL calibration info
Choke - Decay Multiplier
Table of values used to decay out the choke AFR. A larger value will decay out faster.

Seems counter intuitive, at least until I caught onto the point that the "multiplier" is kind of a misnomer, as it really acts like a divisor It's
talking about Time, and when you divide by a larger number, it makes sense that the time becomes shorter, or in this case faster."
--
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid
November 2015.
 
On the choke decay loop, from its description, "Choke Initial Delay", I took that as meaning it first delayed for 5 seconds (cold) or 2 seconds hot
before starting to decay out. Maybe calling it "Choke decay loop delay" or such might make it clearer.

Rich, This only happens at stone cold first startup after sitting overnight etc. It happens within seconds of starting... after giving it maybe a
minute to warm up, I need to rev it up to 1500rpm or so to clear the condensed fuel in the intake.. it will blow a bit of black smoke out the
exhaust.. then its alright for the rest of the day... no more missing. I can shut it off and let it sit for hours and it start right up with no
issues. Never any hot-start issues.

The fact it does it only when cold, and I can clear it before it gets too warm makes me think its not an intermittent connection.

When I rev it to clear the excess fuel there is sometimes a bit of blue smoke too, but not always. I figured that is just from the PCV as I never
need to add oil between oil changes (once a year in the Fall)

I haven't tried a different ECM, but I do have the original Howell unit for a spare. I should plug it in to test it.

Battery is fairly new (2 years). It sits in the shop with the smart converter/charger plugged in so the battery is charged up to snuff. I have an
isolator with a combiner connected across it.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Sir, so possibly you have an injector slowly leaking pressure down when you shut it off causing to rich on next morning start up? Maybe after a hard
run shut it off and pull air cleaner lid and look for smoke like a Q-jet does when the Welch plugs leak. But with the intake blocked it may not get
hot enough to smoke. Maybe put a small piece of cardboard under each injector and look for possible leak - Wet spot? Do you have a schrader valve
in your fuel line? Maybe install a pressure gauge and see how long it holds pressure.

first delayed for 5 seconds (cold) or 2 seconds hot before starting to decay out. Maybe calling it "Choke decay loop delay" or such might make it
clearer.

Rich, This only happens at stone cold first startup after sitting overnight etc. It happens within seconds of starting... after giving it maybe a
minute to warm up, I need to rev it up to 1500rpm or so to clear the condensed fuel in the intake.. it will blow a bit of black smoke out the
exhaust.. then its alright for the rest of the day... no more missing. I can shut it off and let it sit for hours and it start right up with no
issues. Never any hot-start issues.

The fact it does it only when cold, and I can clear it before it gets too warm makes me think its not an intermittent connection.

When I rev it to clear the excess fuel there is sometimes a bit of blue smoke too, but not always. I figured that is just from the PCV as I never
need to add oil between oil changes (once a year in the Fall)

I haven't tried a different ECM, but I do have the original Howell unit for a spare. I should plug it in to test it.

Battery is fairly new (2 years). It sits in the shop with the smart converter/charger plugged in so the battery is charged up to snuff. I have an
isolator with a combiner connected across it.

[/quote]

--
C. Boyd
76 Crestmont
East Tennessee
 
Jim,

When you get older you will pick up a lot of the tricks of the trade.

TIC

> OK,
> First time I heard of using the strobe light to freeze the action of spray.
> One can learn a lot and also refresh the mind by reading these discussions.
> Thank you all for asking and responding.😷

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Have you checked you battery voltage while its missing? That's the reason i asked if you tried starting it on dual battery mode as your voltage may be
on the low side until you spool up the alternator and put a little bit of current into the system.

The other thing is....what happens if you dont hit the throttle and clear it out...does it clear itself?

> Sir, so possibly you have an injector slowly leaking pressure down when you shut it off causing to rich on next morning start up? Maybe after a
> hard run shut it off and pull air cleaner lid and look for smoke like a Q-jet does when the Welch plugs leak. But with the intake blocked it may
> not get hot enough to smoke. Maybe put a small piece of cardboard under each injector and look for possible leak - Wet spot? Do you have a
> schrader valve in your fuel line? Maybe install a pressure gauge and see how long it holds pressure.
>
>
>
>

> meaning it first delayed for 5 seconds (cold) or 2 seconds hot before starting to decay out. Maybe calling it "Choke decay loop delay" or such might
> make it clearer.
>
> Rich, This only happens at stone cold first startup after sitting overnight etc. It happens within seconds of starting... after giving it maybe
> a minute to warm up, I need to rev it up to 1500rpm or so to clear the condensed fuel in the intake.. it will blow a bit of black smoke out the
> exhaust.. then its alright for the rest of the day... no more missing. I can shut it off and let it sit for hours and it start right up with no
> issues. Never any hot-start issues.
>
> The fact it does it only when cold, and I can clear it before it gets too warm makes me think its not an intermittent connection.
>
> When I rev it to clear the excess fuel there is sometimes a bit of blue smoke too, but not always. I figured that is just from the PCV as I never
> need to add oil between oil changes (once a year in the Fall)
>
> I haven't tried a different ECM, but I do have the original Howell unit for a spare. I should plug it in to test it.
>
> Battery is fairly new (2 years). It sits in the shop with the smart converter/charger plugged in so the battery is charged up to snuff. I have
> an isolator with a combiner connected across it.

[/quote]

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
Ok, I'm not the brightest bulb on the tree... I had reduced the choke enrichness setting before but somehow found it just got the mixture too lean and
the idle would hunt up and down.

Today I flashed a modified Bin with the choke AFR reduced by 0.5 for everything 20C and above. My settings are now
-40 5.50
-28 5.20
-16 4.80
- 4 3.00
8 1.40
20 0.70
32 0.50
44 0.50
56 0.50
68 0.50
80 0.50
92 0.50
104 0.50
116 0.50
128 0.50
140 0.50
151 0.50

It started right up and idled nice without loading up. Rev'd up without a belch of black smoke nice!

It still doesn't run as smooth as I've seen other coaches, but maybe its the cam Dick installed?

I'll check it again in the morning.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
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