A/F ratio off?

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DartVadar

DartVadar

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My 360 has always seemed to run really good, good power and everything. For the heck of it I installed a wide-band in it, I think it is running a bit rich. It seems like when it warms up at idle it runs at around 12.7-13.3, and leans out a little bit as you get on the gas, I haven't really charted it too much.

My main issue seemed to happen last night when I was driving home from school. It was really cold out, about 6 degrees Celsius (42 F) so I had to let it idle a bit to warm up, A/F was high 10s low 11s consistently, and seemed to stay around there as it warmed up, and it didn't want to idle in gear, It always wanted to die, idled okay in park. In the morning when I drove it to school it was really nice outside and the car ran great, the only thing I can think of is the cold.
 
I will check that, because its always been kinda finicky, the carb is brand new too.

What should the A/F ratio be?
 
do you get winter blend fuel? best I can tell 12.5 to 14 is ideal, but fuels can affect it
 
FredS said:
do you get winter blend fuel? best I can tell 12.5 to 14 is ideal, but fuels can affect it
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Could be, I just started going to a new gas station, and as I noticed it doing this I got gas on the way home. What exactly is winter gas?
 
You can also adjust your choke pull off. Might need to back it off so the choke is more closed just after it starts. Use drill bits to check gap.
 
DartVadar said:
What should the A/F ratio be?
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14.7 at idle and cruise..... In that neighborhood.... Can go lower to 13.x

Being in the 12's and lower is fat for idle and cruising.....

At WOT, mid to upper 12's..... Need to be at the track and see what the engine really wants for that though.


Hope this helps
 
Aprox 14/1 @ light cruise and 12/1 under power. Engine needs richer mixture
when cold, and you said it was 10-11/1, right? Was it damp out? How's your
wires?
 
If wires are known to be good, and no moisture in dist cap, adjust choke a little
richer.
 
madmoparmick said:
Aprox 14/1 @ light cruise and 12/1 under power. Engine needs richer mixture
when cold, and you said it was 10-11/1, right? Was it damp out? How's your
wires?
Click to expand...

Seems like I am rich then.

And yes that is correct, when I started it initially when I finished school it was around 10-11:1 but even after it warmed up It didn't really lean out too much, probably mid 11 after driving it for a while. It actually just rained a bit and was super windy, the wires are good, new cap, plugs. Everything only has about 1500 miles on it.
 
14.7 is optimal fuel mixture for pump gas. The higher the number the leaner she is. The lower the number the richer. I am dealing with a rich issue myself so I am learning along with you. If it is in the 10-11 range on initial startup and stays there after warm, it sounds like the choke is not turning off. Loosen the three screws and turn it clockwise to adjust that.

DartVadar said:
Seems like I am rich then.

And yes that is correct, when I started it initially when I finished school it was around 10-11:1 but even after it warmed up It didn't really lean out too much, probably mid 11 after driving it for a while. It actually just rained a bit and was super windy, the wires are good, new cap, plugs. Everything only has about 1500 miles on it.
Click to expand...
 
14.7 is not "optimal"... it's just a number to show that every fuel-particle is being burned with every air-particle.

What the actual 'Optimal' number is what your engine wants/needs, (for best idling/economy/power/cruise rpms), you can only check by trial and error, measuring mpg, butt-dyno or chassisdyno.

As long as there is no load on the engine, you could tune as lean as the engine still wants to run nicely.
But all depends on the efficiency of the engine.
 
True, the 14.7-1 is the "Stometric" ideal number. I have constantly gotten better fuel mileage with a slightly leaner mix. But that fuel mileage and what I was after. (At least with the primaries only while just driving.)
The secondary wide open throte mixture is run on what drops the E.T. In which is good for the track conditions. On the street, the same or close to it is what your after. Running a lower E.T. Jetting my not be what you want for the street. But it gets the job done and mileage, at least when I'm in the secondaries, is of no concern.

Take your time tuning.
 
Just an update on the situation up until now.

I just started it up to take it for a spin, it started up fine, I was just letting it warm up a tad because its pretty cold out, no backfiring or running rougher than usual. As I started driving I noticed it backfired once when I hit the gas, so I stopped and checked everything (never backfired before), it was idling and running great (still a bit rich A/F though).

It seemed like it was running funny, kinda surging and stumbling occasionally, so I got off the highway and pulled into a parking lot, it was idling just fine no noises or anything. So I pulled out of the parking lot and It was running like absolute CRAP!! didn't feel like it had any power and stumbling a whole bunch, felt like it wasn't getting fuel (but why would it backfire if it wasn't getting fuel??), also the wideband read 10:1 for a while. So once again I pulled over, and this time it was idling funny, so I stopped and looked things over again, I though maybe the timing changed, but everything was tight. Everything seemed fine to limp it home, so I started it up and it was still running like crap! didn't want to idle, and surged like crazy as before. On the way home it started to run like normal all of a sudden, no surging or power loss. It seemed like the running like crap was intermittent, as I got home it was running fine again. The choke wasn't stuck as mentioned before either.

The only thing that I changed was getting gas, before I got gas it was running like a champ, so I am thinking that I could have gotten a bad batch of fuel or something. Maybe some water got in the tank? I have put at least 1500 miles on this car with the new setup and had no issues at all. Don't think its a vaccum leak either, but who really knows...
 
Pull the fuel line and coil wire. Crank it into an empty water bottle to check for water or particulate matter. I had a new Edelbrock with debris in it.
 
fratzog lover said:
Pull the fuel line and coil wire. Crank it into an empty water bottle to check for water or particulate matter. I had a new Edelbrock with debris in it.
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I will try doing that tomorrow. But I had some gas line antifreeze handy so I put some of that in the tank, and took it down the road, It seemed like it was alot happier, at idle it seemed like it had a random popping out of the exhaust, not loud or anything, and It didn't do that when It was colder when I started it.
 
To update on the popping I checked the rocker arms and nothing is loose, pushrods are spinning away (don't know why but I'm always worried about the flat tappet cam! LOL) What would cause an intermittent popping in the exhaust? Nothing through the carb. Its only on one side of the exhaust (true duals) fouled plug maybe?
 
BigBlockMopar said:
14.7 is not "optimal"... it's just a number to show that every fuel-particle is being burned with every air-particle.
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correct though i would add "theoretically". and 14.7 its not even stoich for "pump gas" which is not 100% gasoline. FTR the ECU in my Neon commands a target A/F of 14.36. besides if that was the "right" mix why would you need a CAT to oxidize all the fuel that didn't burn? Ive leaned out my mixture with my wideband and would get a few MPG better. Lean past 16.8 and drivability suffered. I would lean it out so that at part throttle cruise the downstream O2 sesor would through a code thinking the CAT was failed. I have no idea if a carb engine with huge cylinder bores, and a less efficient combustion chamber would like such lean mixtures. Missfires KILL mpg and lean mixes are harder to ignite.

Anyways, going from 36 to 39MPG in my commuter is a LOT less gas saved than 13 to 16MPG ;-) so i doubt it is even worth the hassle on these old cars. Your ROI isn't going to be there if everything else isnt 100% perfect. FTR when i could buy it E0 gas was a few MPG better than E10, summer blend was a few MPG better than winter, and A/C definitely affects MPG.
 
Took a few plugs out and they all look like this one, they are all dry, so not oily, but there were all full of carbon/soot, checked the plugs not long ago and they looked the correct tan colour. Seems like they were fouling and thats what is what mostly likely caused the slight misfire. I know I was running rich before but would it all of a sudden run like crap? And are the plugs still good?
 

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My little iPhone and missing glasses only allow me so much focus this morning... LOL!

Try cleaning them up first. If not, plugs are cheap. ;)
 
Plugs are still good, but clean them because the carbon can cause them to loose spark (shorts thru carbon). I applaud you for installing a wideband O2 sensor. With A/F in the 10's, you probably have black smoke from the exhaust. You verified that the choke plate is full open when it runs rich. The main other thing to cause "too rich" is if the fuel bowl level is too high, or overflowing into the throat. That is commonly caused by debris in the needle seat, which is easy to remove and check in most carburetors. The float can also sink, but your carb is fairly new. One other thought is if you have the "heated air inlet" as in ~1973+ cars, if the diverter door in the air cleaner sticks in the "hot air" position, it can run rich. That happened to one friend in a Ford Escort soon after those things came out. On a long trip, they started getting 10 mpg and found a stuck door was the problem.
 
What plugs are those? You may want to try a hotter plug to help with burning the fuel better.

I too have a Wideband installed. It is a great tool to get you into the ballpark.
 
Mad Dart said:
What plugs are those? You may want to try a hotter plug to help with burning the fuel better.

I too have a Wideband installed. It is a great tool to get you into the ballpark.
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It really is, I am glad I installed it. And they are NGK with a 7 heat rating, I have been playing around with the plug heat rating and the 7s seem to be pretty good.

And the problem was the fuel! I siphoned a bit out of the tank and it looked and smelled odd, really dark in colour, had gas from that station before and it was almost clear, wonder if it was old? So I siphoned most of the fuel out and drove into town and filled up with some fresh gas, I am going to clean off the plugs tonight but its already back to its old self, not misfiring anymore and has lots of power, also the wideband stabilized alot more.

I was talking to a few buddies and they have recently had bad batches of gas as well, complained that their cars just weren't running right.
 
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