I started a thread a couple of months ago trying to get to the bottum of this freakish leaning symptoms I'm having when my car goes into open loop. Here's the link if you're interested in seeing additional photos or vids on the subject.

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

Anyway, below is some datalogging I did yesterday with my wideband LC-1 comparing what my AFR's look like when the car enters open loop mode, ie, when I plug my boost sensor in. The highlighted areas are when I'm giving the steady throttle input and halfway through I increase the throttle input. You can see the first test it hovers around 14.5ish then drops to the 12's when I increase the throttle input but when the boost sensor is connected and the same exact test is run drops the 15's during light throttle applications and then as far as the 18's when additional load is applied. The car is very unresponsive, stutters very hard, and has a very potent smell to the exhaust during these lean symptoms.

I know there is a handful of people on this forum I have come across with a similar problem, none this extreme to my knowledge, but I need to get to the bottum of this so I can actually tune the damn car!

Help would be greatly appreciated!!

Thanks,
~Ant

p.s. the non-highlighted parts are the car at idle and the sky rocket spikes are when I release the throttle from the rev, just fyi

 

So for the first green section, was this while driving around or free revving? If going from cruise to moderate acceleration, that looks pretty normal. At closed loop you should be around 14.7 AFR, and under acceleration, you should drop down into the 11-12 AFR range. This is the closed loop to open loop transition (at 37 seconds).

The 20+ AFR spikes look normal too, if you let off the throttle under decel, then pushed the clutch in right away. I can't really comment on your numbers without a boost sensor, since I've never tried to datalog under those conditions. Have you tested the boost sensor itself?

 

...I shouldn't had posted that right before I went to bed. The first highlighted section is free revving without the boost sensor in closed loop, it acts normal there. The second section is free revving with the boost sensor plugged in, so when it goes back into open loop it starts leaning out....my fault ...

I've tried replacing the boost sensor with a friend's who didn't have this problem and it acted the same, I believe in this case the boost sensor is just switching the car between open and closed loop and exposes the inconsistencies between the two...in which it shouldn't be so drastically different

Here are the correct titles

 

any educated guesses?

 

Should there be that much static in my AFR readings for one? I found that my 02 sensor wire is almost completely ripped off in one section so I'm going run a clean wire for it and see if that helps any....

 

test your sensor wires at the ecu then test the same on your buddys car, you will found out for sure if the wires are the cause or not

 

I like that idea, so say the voltage I'm getting is irratic if/when I test both sensors, would that mean the ECU is the issue?

 

I'm getting a constant 12.5 volts to the pressure sensor while the car is running. Getting around 11.8-12v with keys set to on position. Checking the codes while the car was on it said again that my 02 sensor was bad even though I replaced the wiring to it and its fairly new. Is it possible that the 02 sensor can go out that bad and cause these problems?

 

Guess this forum is a pretty dead during the summer?

 

it's this subject, if you remember i had this problem too, and still do to a mild extent, but i'd be intaresting to see what my AFR's are with a wideband. i need to get a bung for mine still.

i would try replacing it your narrow band, and report back, there less then 20 bucks, my rtek shows normal voltage when cruising so i'm not real sure, but i did have a fuel pump problem that cured most of my closed loop issue.

 

Will do, I have a feeling it's not the problem, but it never hurts considering how cheap they are now.

 

Ah fudge. You want to look at the OUTPUT of the boost/pressure sensor NOT whatever you've been looking at.

Free rev............does that mean sitting in the driveway reving the engine up? If so, who cares. It's meaningless.

02 sensor is in open loop when the car is not being driven and only goes into closed loop if the rpms are over something like 1500 rpm while driving.

Any time when driving and you let off the gas pedal, the ECU initially cuts fuel from the front rotor and if you let off enough fuel to both rotors is cut until either you get back on the gas pedal OR the rpms drop down to around 1300 rpm whereupon the fuel delivery resumes.

 

DO THIS
Datalog your wideband at around 50 or 60mph and let it go into closed loop, and back to accelerating and back to closed loop. then do it without the map sensor plugged in..

 

ran a new wire for my 02 sensor to the ecu and rewired the fuel pump to receive 12v at all times...at the moment, problem no longer exists!

 

badass... wondering which thing solved the issue im about to do the fuel pump rewire... are u running stock s4 alternator?

 

Golly gee whiz. The ECU will not ever ever ever ever ever ever ever ever go into closed loop sitting in the driveway........unless you follow the FSM instructions and unplug the TPS and either disconnect the neutral switch at the transmission OR in lieu of that push the clutch pedal in and hold it in. Then the 02 will go into closed loop as the engine is rev'd to approx 1500-1700 rpms.

 

I didn't know that before hand but the 'stuttering' and 'leaning out' problem that had existed previously would happen regardless if I was free revving or in gear driving. I just changed the 02 sensor wiring because I couldn't get the error code to go away despite buying a new 02 sensor and rechecking my soldering connections. I just ran a wire from my wideband to the gray wire at the ECU and life was much smoother afterwards

 

what about my post?

 

yup...

here's the link that I referred to for the fuel pump rewire https://www.rx7club.com/nw-rx-7-forum-33/name-fuel-pressure-issue-870743/. Pretty straight forward, didn't take all that long to do.