When I’m coasting or at idle my afr’s are in all over the place btwn 17 - 21’s. Is that normal…? It’s a Mikuni carb that I haven’t touched a jet on. It could very well be for a 12A, I have no idea…?? I’m running GSL-SE rotating assembly & she runs good everywhere else tho, cruising, pulling, top end… I mean what I think is good enough not to pop a motor (rich).btwn 11-14’s. Any input is appreciated.

 

yeah, i have the Mikuni catalog somewhere amongst my old rotary stuff. i don't think there was a 13B application - at least, i don't remember one.

if you can still get jets for them, maybe you can find some that will help you get it richer. if not, then maybe you can get what you can and modify them to suit (solder and/or a drill bit).

 

I have a Mikuni book somewhere too. And there’s (or at least was) a guy on eBay who sells all sorts of jets for Dellorto’s. They’re prob the same or if not I bet you can get Mikuni jets all day being they use them on all sorts of motorcycle carbs…

So lean on idle and coasting is not normal…??

 

i don't think lean, in and of itself, is that bad under those conditions, but i don't know how lean is acceptable. 21 just seemed crazy to me is all.

this is for Nikki, but i think it should apply in general: https://www.rx7club.com/1st-generati...nikki-1147611/

how is the car behaving?

 

a rotary engine without the airpump won't run at 17:1, and then if its jumping its telling you its misfiring.
probably too lean, but you'd have to test it.

 

It seems to be running fine. She has new plugs, new wires, new cap, new rotor, a MSD 6A firing both leadings. I didn’t notice it before you mentioned but it does sound like a misfire only on idle (which I do have pretty low, 800). I also have a Innovative AFR meter https://www.rx7club.com/1st-generati...rm-up-1160744/ They’ve been known to have all sorts of problems. I’m also now rembr’n my O2 bung might be installed a bit too close to the motor. Maybe time to give my AEM afr a try and see if I get the same results vs possibly chasing ghosts…

 

i've noticed that my ECU, which is looking at the AFR 20 times a second will pick up a misfire way before i notice it. also i've noticed that the display is a lot slower than the data feed, so its not actually that useful
with my car as i lean it out, the AFR gets unstable, and then the vacuum drops off as the misfire get worse, at some point the AFR is just throwing bogus numbers

but you should try doing a sweep from rich to lean, or lean to rich and see what happens

 

Being super lean at idle, even if you can stabilize it, will still unnecessarily soak the system with heat.

 

These guys have some Mikuni jets:
https://power-barn.com/search.php?se...ery=mikuni+jet

I have no affiliation with them, I just remembered seeing Mikuni jets when I bought some Hitachi jets for my Nikki (they're a perfect fit)

Hope that helps.

Jon

 

So the Innovative AFR is def all over the place but it wasn’t wrong being pegged lean on idle as each day I daily drove her to work the symptoms progressively got worse and worse. I cleaned out my 100 micron Aeromotive fuel filter btwn the tank and pump and then cleaned another filter (40 micron) right before the carb. I then took the main air jets and idle jets out, carb cleaner sprayed them + compressed air and it’s running great again while holding an idle nice and smooth. Innovative AFR still radically ALL OVER THE PLACE. 😬. I have the day off sooo it’s hopefully to find and install my AEM afr.

 

Also ordered a 10 micron filter to put before the carb and the 40 micron will go before the regulator…. See how that goes.

The vent was clogged as well so for now shes just a hose off the tank w a check valve.

Innovative AFR seems to be working again on the trip into work. 🤷🏻‍♂️

 

I'm between 14-18 on decel, which is normal for a motor to lean out at that time.

Otherwise, 11-13AFR on idle and under load. 83GS, stock port, holley 600 (too big, dont need the lecture lol), RB filter and carb hat, RB intake manifold, full exhaust, holley red fuel pump (at 6psi) and FPR, AEM wideband.

 

If you have an Innovate reading 17:1 at idle... the sensor is bad or you have an exhaust leak.

I can't get a stock port to idle well any leaner than 14:1 and it much prefers 12-13:1.

Innovate gauge type controllers are trash, they have poor circuitry that kills sensors. Just cooks 'em. I have had much better luck with the AEM unit.

 

Someone in another thread (I posted the link a few replies back) said to use a diesel sensor and it actually seems to still be working. She went pegged 22.4 again, which is the highest # but I figured out the top that covers the jets was loose as I went to clean the jets again…. Instead of pulling cover and cleaning jets I snugged the screws to the cover down and at least it went back to 17’s again. I also noticed the choke was slightly open so I added a spring to hold her fully closed. I rembr reading somewhere before the choke on a Mikuni acts a vacuum leak I believe…. It’s been awhile, anyway when she’s open it def goes lean af. I do have an exhaust leak & didn’t know it’ll cause a lean reading. Thank you.

 

Generally speaking a wideband sensor will read lean when it dies. Depending on the sensor and controller in use this could mean a reading anywhere from 17 to upwards of 30 is displayed. It's actually pretty common for ECUs to include a feature that disables EGO control if the sensor reads that lean for a certain amount of time because it almost always means a dead sensor.

As some other folks have said, it's impossible for the car to be idling at 17:1, let alone 21:1 unless perhaps you have an air pump hooked up. Dying sensors can also work intermittently, so if it's coming and going I'd personally suggest trying a new sensor. The exhaust leak certainly isn't helping either however.

 

At idle or coasting it’s in the 17’s - 20’s. As soon as I get on the gas pedal she goes 12’s - 14’s even at WOT. I’ll hook up my AEM AFR just to verify the Innovative is working properly I just can’t find her in the sea of parts I have in my garage atm.

 

You must have an exhaust leak upstream of the sensor. It is pulling air in and faking the sensor out.

 

Yes I prob do. This block had a stripped exhaust stud that I sent home as best I could accompanied by some JB Weld on the threads. I’m going to have to revisit it.