wideband reading lean
 

this has been happening for a while now and i'm not too sure why it is... i have the rtek 2.1 update and when i go start my car in the morning i let it warm up to 100 degrees and take off. when i start driving under very light throttle my wideband start reading higher then 15 and hitting 17 and 18's!!! then i gas it, it stumbles and then starts going and the mixture richens up as it should. i thought maybe it was my tune that was doing that so i reseted the computer and put everything back to stock and it still did it wheather it's cold or up to operating tempeture it still does it, specially when the car is at operating tempeture and i shut the engine off and start it again, then it'll start getting lean again under light throttle. After like 5 mins of driving it goes back to normal and the fuel mixture is fine under light throttle. I checked the temp sensor for the computer and its working fine.. i compared the reading it gives me on the palm against my gauge and they're really close, i looked for any error codes and there's none, it doesn't make sense to me how it only does for about 5 mins after i start the car, even if it's already up to operating tempeture, anybody have any suggestions?

Wierd. Maybe check your fuel filter?

i forgot to mention that i'm running S5 N/A rotors so when the car was running good it would run really rich, and i know it's because of the higher compression rotors. I don't understand how it could be running lean if i'm running the higher compression rotors... also i notice the car starts acting more when the engine is already at operating tempeture and i turn the engine off and i go back to driving it 5 mins later and the wideband starts reading really lean, and after some driving it runs normal again and the wideband begins to fluctuate again as it should. i looked at the car's narrowband O2 reading and it also looks fine, it goes full rich when i gas the car and fluctuates when throttle is steady. ALl sensors seem to be putting out normal readings. anything i should look at?

Wow seems like I'm not the only one having this issue.

Does your car have an operational airpump and ACV?

Or is this just a matter of the ECU going into closed loop (as in the 02 senor is now in the loop) once driving?

Airpumps deliver air to the ACV which in turn sends fresh air to the exhaust ports. Exhaust ports being prior the location of the 02 sensor itself. Which would explain a reading that is showing lean when the actual mixture isn't at all lean.

Rats nest has been removed. My AVC, EGR and OMP are all blocked off.

did you change your injector size? set the correct fuel injector size, rtek 2.1 has presets, my 550/720 set up needs to be tuned down by a bit to get 14.3-14.7 at no boost. i'm reading 10-12 in wide open throttle. I will run lean (17+) when i let go of my throttle when i'm reaching 80+km/hr

If your wideband is anything like the AEM units, take a rag, spray brake clean on it, and cover the end of the sensor..it should go rich and stay rich. (once it has warmed up) if it doesn't do this than it could be bad.. Mine failed this test, this is how AEM tells you how to test it.

and check you fuel filter. had a simliar problem only after 6 months.

My car did the same thing. 550/720 injectors where ok. 720/850 was crap, 850/720 worked finebut the criusing areas are all over to keep the weird lean spikes down. Now I'm running 850/1000. It runs fine now but still hits 15ish randomly and stumbles during crusing. I just find it weird. I'm using the injector set mentioned above with the 720/720 preset and I'm only -0.2 in the fields where it hits 15. I figured I should be in the 12s lol.

Bump, my car is doing this EXACT same thing described in this quote.

It either started when I installed the rtek 2.1 or it is just a coincidence, I was running a rtek 1.8 for over a year with no issues before this.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/light-throttle-hesistations-lean-symptoms-889547/

This thread also describes the issue, and it seems everyone in that thread with the same issue has a rtek of some sort.

I'm going to throw my 1.8 back in and see if it does the same thing as my 2.1

Mine was doing this same thing. I have 720/1000 CC injectors. I changed to the 550/725 setting and it seemed to take care of it.

Has anyone found a real cause to this issue? I'm having the same issue now too. Car ran great for a few years on the 550/550 setting. This winter I upgraded my fuel system with a walbro pump, 720/850 injectors, aeromotive fpr, new filter, etc. I had an issue with it idling wrong which I traced back to it not charging properly. Also had an issue with the tps sensor so I bought a new one from mazda (almost $300 cnd). Yesterday I switched it to the 550/720 setting instead of the 720/720 setting and it's now drivable again. You can still see the issue exists though on the wideband. Cruising around and light throttle it sits around 14 most of the time, but then it will go into the 12's every now and then under the same conditions. Switching settings just kind of masked the problem with more injector duty cycle. Any thoughts? I still have a stock throttle body. I was thinking maybe something isn't working properly on it, but it ran fine last year and I didn't touch the throttle body other than to remove the throttle cable.

it has to do with injectors sizes and the staging you pick out... at the end of the day any combination can be made rich enough when the computer goes into closed loop.. but with some injectors/combinations the other areas will be even more overly rich to the point you subtract fuel everywhere.

This is happening just while driving under light load, low rpm so this is just when the primary injectors are being used. They are 720 cc denso injectors. I checked the part number and had them tested. It seems like something is just switching randomly to give it more or less fuel. On the 720/720 setting it would work fine when cold and would work fine sometimes randomly when the engine bay temp was hot. When I get time I want to get my lab scope out and scope both secondary injectors while driving and see if I have one that is acting weird.