Hey all,

I tried searching but didn't find any definitive answers.

I installed the PFC last Sunday and have noticed that my car is not going into closed loop operation during cruise conditions.

The O2-feedback is turned "on" and I'm getting voltage readings from the O2 sensor.

During cruise on the highway, I'm reading 0.93V from the o2 sensor (rich enough for you?). It should be oscillating between a low and reasonably high voltage (0.4 to 0.8 or so?).

Does anybody have any ideas?

 

I recall a post from a couple of years ago where someone claimed that closed loop would only be functional for cells where the injector duty was less than X.. and I forget what that was. This was pre datalogit, so who knows if it was reflective of just the correction factor, or the total of the base + correction. A figure of 1.06 correction or something comes to mind as the limit mentioned, but it's all fuzzy now. This sound familiar to anyone?

Did this just start happening? Maybe after you loaded/modified a map?

Edit: I just re-read your post, and I see you just installed it. Who tuned it before you?

 

Are you getting any codes?

 

One question, is the air pump on your engine and working? If not you turn the O2 control off.

 

Thanks for the comments guys.

TwinTriangles: You don't get codes with the PFC but, no I didn't get any codes with the stock ecu.

Chuck, I am still running the air pump and it does work. I am still running the stock base mod map except I have cleaned up the two cells of negative split and have added 0.003 fuel to the cells in the P5N5-P9N10 area (the ones that are all at 1.000). I did this to clear up a little bit of surging I had at light throttle/low rpm. None of these changes had any effect on the closed loop problem.

FWIW, I suspect I had this problem with the stock ecu as well but didn't know (I just thought 15 mph city/highway was on the low side of normal). I don't understand why it wouldn't work if the o2-feedback is turned on and I'm getting good voltage (or am appearing to) from the o2 sensor.

Other than this, the PFC seems to be working well. The car pulls harder, despite the fact that the maps are still way too rich. I do have the A/C problem, I was hoping I wouldn't have it with my 95 but.....

 

Not to second guess, but the PowerFC is notorious for surging on closed loop. You sure it wasn't working before you added the fuel?

 

Nope, I did a long highway drive before I made any fuel map changes (just cleaned up the 2 neg split cells). The O2 sensor was reading low .90s voltage then too. I raised the fuel in those low load/low rpm cells on my mechanic's advice, and 0.003 is the least amount of change you can do.

Actually, since I'm asking, what type of o2 voltage should I be seeing at idle? I am currently seeing ~0.17 volts.

 

Make sure the O2 sensor is function correctly. With no Electrical load on or AC, get the car warmed up while driving. In 4th gear run it up to about 85 or 90 mph. Have the PFC in the sensor/switch display and let off the gas while still in gear. The O2 voltage should drop all the way down to .01 or .00 since there's no fuel being injected. Anthing higher than .03 means its on its way out and is giving bads info to the PFC. Mine was showing .15 on the same test with WOT voltages reaching to the 1.17 range. Nice for a part that is supposed to be up to .99

Tim

 

Why is this? Mine worked in close loop without the air pump. Good thing too, it helped me nail down a magnificent 17 mpg vs 12 mpg when I turned it off after I broke the O2 sensor wire.

At 120 km/h I was in closed loop, at 130 km/h it went to open loop. I believe this was RPM dependant, I think the closed loop only works below a certain RPM.

 

Zerobanger seems to be onto something with the AC/PFC problem. My AC works on setting 1 but not 2,3, or 4. But it works on 1.5 and 2.5 which is basically 2 and 3. In other words at a dead stop, turn the AC setting past the 2 setting slowly and you'll hear the condensor kick on. Mine still doesn't work on 4 but who cares. Setting 3 or 2.5 with the PFC is good enough for this heat we've been having. Try it...

 

Zerobanger seems to be onto something with the AC/PFC problem. My AC works on setting 1 but not 2,3, or 4. But it works on 1.5 and 2.5 which is basically 2 and 3. In other words at a dead stop, turn the AC setting past the 2 setting slowly and you'll hear the condensor kick on. Mine still doesn't work on 4 but who cares. Setting 3 or 2.5 with the PFC is good enough for this heat we've been having. Try it...

 

Thanks for the tip Barry, but I'm already all over that one -- I live a mile from Zerobanger and he was there when I fired her up with the PFC for the first time......

So, are you going to hang out here a bit after you sell your car or will it be too painful...

 

Thanks for the advice Tim, I will try that out tomorrow and see what happens. AFAIK, the o2 sensor is original at 71k miles -- it's probably nearing the end of it's useful life....

 

I'll check back here from time to time to see what interesting debate is going on. I'm glad to see you're moving up the modding scale with the PFS IC and PFC. Soon, you'll be where I was. Did you notice the PFC smoothing things out?