Went lean...

[Phreakish]

It sounds like the answer is in the breather setup. Got any pictures of your engine, air cleaner, breather hoses, breather filter etc? Seeing how yours is setup would probably help people visualize if a change to anything might explain your experience.

It sounds like you stopped, fiddled with the air cleaner, and suddenly your idle AFR is dead lean and your WOT afr went from 10 to 13.5 and that neither is a huge concern except you don't yet understand why it happened.

The added info that the behavior or you car changed in the expected way along with the change in the AFR reading is also hugely useful - we know something did actually change with the engines operation. Like Rat alluded to, the AFR can change due to sensor/gauge behavior when in reality nothing in the engine changed. I've experienced exactly this when my O2 sensor on my EFI decided to die over the course of about 20 miles on my way home - 'twas not a fun ride, and the following week of fiddling sucked too.

 

[7milesout]

It sounds like the answer is in the breather setup. Got any pictures of your engine, air cleaner, breather hoses, breather filter etc? Seeing how yours is setup would probably help people visualize if a change to anything might explain your experience.

I'll try to get some pictures tonight, if I can get to it before dark.

It sounds like you stopped, fiddled with the air cleaner, and suddenly your idle AFR is dead lean and your WOT afr went from 10 to 13.5 and that neither is a huge concern except you don't yet understand why it happened.

YES! My ability to be clear is not great. Your comprehension is great.

The added info that the behavior of your car changed in the expected way along with the change in the AFR reading is also hugely useful - we know something did actually change with the engines operation.

Yes. It did as you state.

Like Rat alluded to, the AFR can change due to sensor/gauge behavior when in reality nothing in the engine changed. I've experienced exactly this when my O2 sensor on my EFI decided to die over the course of about 20 miles on my way home - 'twas not a fun ride, and the following week of fiddling sucked too.

I can understand this totally. But mine did not exhibit this. It responded to the change in AFR. Sounds like my engine responded to some unknown change. Your engine's performance responded to a sensor that was lying.

 

[Rat Bastid]

I'll try to get some pictures tonight, if I can get to it before dark.



YES! My ability to be clear is not great. Your comprehension is great.

Yes. It did as you state.

I can understand this totally. But mine did not exhibit this. It responded to the change in AFR. Sounds like my engine responded to some unknown change. Your engine's performance responded to a sensor that was lying.

The sensor doesn’t lie. It can only measure oxygen content in the exhaust. So it can’t tell the difference between a lean miss and being rich because there is so much unburned fuel left over from the misfire.

That’s what I’m trying to get across for anyone using an O2 sensor. Just because it’s saying something it doesn’t mean that what’s actually happening.

I’m still looking for the other paper by Shrinker. I know I have a copy at home. In it he discusses working with an engine on the dyno and the O2 was saying one thing but the end of it was something else was happening. It s a great paper.

My point is just don’t take the O2 sensor reading as gospel. Look at it and then look at everything else around it and then you make the decision on what’s happening.

You can get into a similar situation with EGT’s. I had a customer call me one day from the track and his EGT’s were horribly high. Like over 1500 degrees or something. I asked him what the plugs looked like and he never checked them. So I asked what was doing to lose them and said he was adding fuel and pulling timing.

So that was the answer. He had delayed the combustion process so long that there was still combustion happening when the exhaust valve opened and that was what the thermocouples were reading. They weren’t wrong. The tuner just didn’t correctly assess what the data really said.

So I had him add timing and pull a bunch of fuel out of it and the EGT’s were right back in line.

It’s easy to get data overload and become data dependent. One or the other isn’t good, but if you happen to be at a place where you are doing both you can get lost very quickly.

Hopefully that clears up my original post.

 

[7milesout]

The sensor doesn’t lie. It can only measure oxygen content in the exhaust. So it can’t tell the difference between a lean miss and being rich because there is so much unburned fuel left over from the misfire.

That’s what I’m trying to get across for anyone using an O2 sensor. Just because it’s saying something it doesn’t mean that what’s actually happening.

This advice is how the 3 Mile Island accident happened. They didn't believe or trust a gauge reading. I'm not able to be clear, that it went lean. It didn't go lean and misfire and fail to run. It just went lean. Leaner than where I had it tuned. Immediately upon this event. Had I not had an AFR gauge, I probably wouldn't have noticed.

I’m still looking for the other paper by Shrinker. I know I have a copy at home. In it he discusses working with an engine on the dyno and the O2 was saying one thing but the end of it was something else was happening. It s a great paper.

My point is just don’t take the O2 sensor reading as gospel. Look at it and then look at everything else around it and then you make the decision on what’s happening.

And I'm trying to explain to you (but somehow not being clear) that, I DID. The engine performance responded in kind to EXACTLY what the O2 sensor was indicating. Under light light load, the AFR would go up to 20 or maybe even 21. And the engine at low rpm and low load would respond very weak. However when enough vacuum signal was lost due to rpm, the metering rod springs would back out the metering rods, fuel would flow, the AFRs would drop to perfect and the power would come on very healthy. So, I observed what was going on. My AFR gauge was correct, accurate, I believed it and everything else meshed.

 

[7milesout]

I FOUND THE PROBLEM! And, pictures.

I went in this morning to re-jet based on my new found problem. And during the course of doing this I told myself I'm going to put that air cleaner assembly on piece-by-piece very carefully.

I have a habit of removing the wingnut and lifting the whole air cleaner assembly off in 1 piece, and then pulling the breather hose off and setting that aside. Which I did again this morning. But I decided I was putting it together piece-by-piece. After changing the primary main jets, I sat the whole assembly back on and realized, this is not piece-by-piece. So I pulled the top and filter off and this is what I observed.

I think I indicated in my first post I noticed this breather vent was out of position. But I was talking with my new friend at that time. I did straighten it up replacing it. But I didn't notice just exactly where this breather vent was when I pulled it off. When I pull that whole assembly off, with the top on, and handle the breather hose, I've been rotating it out of position, and didn't know it. So, now I know.

The AFR gauge pointed out the difference IMMEDIATELY. I trusted it, I just didn't know why the AFR changed immediately at that event and it made me a bit nervous. Now I know. And now with my new found undisturbed air flow, I get "MO POWER BABY." (Say that like the guy on youtube.)

This also answers why my choke never seemed to work like it had before. I was basically choking it to some level 100% of the time.

The retune begins. Based on my nerd spreadsheet, what I observed with the AFR when it went lean after "the event," and my re-jetting this morning, the "cruise" mode and "power" mode are already spot on. Now I will confirm the WOT next chance I get, do the math, refer to my nerd spreadsheet and re-jet the secondary main accordingly.

Thanks for helping me out guys!


7milesout

 

[oldkimmer]

Glad u found it. U were asked several times to check it and never did. A simple fix that wasted our time and yours. Kim

 

[7milesout]

Glad u found it. U were asked several times to check it and never did. A simple fix that wasted our time and yours. Kim

I was asked several times to check WHAT? I never did? This thread started on Wednesday. This is Friday! I'm not sitting around at my house all day, I've got a job that requires long hours going at it. What was I supposed to find? Prior to Tuesday this piece was blocking airflow, but I had tuned for it. After Tuesday I had inadvertently FIXED the problem, but had never realized that what I "fixed" WAS the problem because I didn't notice exactly where exactly it was when pulled that assembly off.

After meeting this guy, I had put it back in correctly. So, taking it apart at that time per your "asking" was supposed to find what? It positioned correctly? I was asked several times to check? To check that the part I moved into the correct position was in the correct position? Brilliant.

It was because I went in to tune, and was checking myself during assembly that I stumbled upon what was happening during previous instances of pulling off the air cleaner. There was nothing to "check" from the time of this event with my new friend.

If this was such a waste of your time, what are you even doing on a forum? Damn, what a a-hole response...

Do me a favor and never respond to another thread of mine. I don't want to waste your precious time. You've got squirrels to yell at, neighbors to yell at, and a blinker to cancel.

 

[fishmens67]

I don't see how that breather caused the lean condition you were experiencing.
If the vent was interfering with the choke operation I would think a rich condition would be observed.
I'm glad you got it fixed, I just don't know how.

 

[7milesout]

fishermen67 - In that one picture you can see how it was hanging over the primary side. Somewhat blocking the primaries. Like a choke. It had been in that position for a long time, due to me removing the entire assembly, and not looking at that piece inside. So I had tuned for that amount of air blockage. Since I had tuned for it, it wasn't running rich.

Upon "the event," talking with my new friend, he wanted to see the AVS2, I pulled the assembly off. At that point, while distracted talking to him, the air filter assembly didn't come off as one piece due to my distraction, and I wound up with the upper, lower and filter separated. I then noticed it wasn't straight sitting in the lower. At that event, I put them back on the carb in 3 pieces and "fixed" that vent back to where it is supposed to be. Never thinking or noticing (at that time) that it had been so far out of position, it had been hanging over the primary. So when I put it all back together correctly, blam, extra air flow (not tuned for) due to not blocking the primary, and the AFR gauge noticed.

I just drove it out to lunch. The primary side tuned is now good. Feels like EFI when at speed. It idles good, meh ... better, chokes correctly. It's very nice. I'll tune the WOT later. I've not been happy with the AVS2 since I put it on. And this previously unrealized blockage was the culprit. It did drive ok because I had tuned for the blockage previously not knowing that it existed. But I always felt something was off. Now I get to have fun fine-tuning it to perfection. I'll of course always check this vent. I'm going to replace the PCV valve and breather components due to all this.

 

[George Jets]

 

[Phreakish]

If it were my car, I'd get rid of that breather thingy, or fix it so it can't rotate out of position again and block the choke. Better yet, just run a filtered breather rather than having that thing hooked to the air cleaner. I'd rather wipe off valve covers occasionally than burn oil. Besides, if something goes wrong (overfill of oil, broken ring, bad head gasket), I'd rather the breather make it obvious by rust-proofing my engine bay than by burning a ton of oil that's sure to cause additional repair costs. Just my $.02

I'll also add that such a significant change in AFR should be felt by almost anyone, and that changes in performance should be cause enough to look for what's different, or got bumped the last time something was tinkered with.
The WBO2 helped in this situation, but I'd hope a shift from 10:1 to 20:1 would cause enough difference for even a causal driver to think 'wtf just happened' ;)
Just as many people who find a problem that's indicated by an O2 sensor as chase a bad sensor with tuning adjustments - and the internet being what it is, folks will chase all kinds of odd things based on a vague description. Luckily in your case, you had corroborating information that made trusting the gauge a wise choice. That's not always the case, and luckily people reading this thread years down the road will know that based on some of the questions and clarifications posted.