After driving around for a month with the Walbro I finally got my FP gauge installed so I could adjust the FP with my Nismo AFPR. Before tuning my FP was around 100!! Right now it's around 42.

I have a wideband O2 sensor and during WOT it's in the 12's, which is good enough for a rough tune. However, when I got home I noticed that my A/F ratio didn't settle back to 14.7 when I was idling. It actually shot up to 20, back to 15, then back to 20. It looked like it was on a cycle.

One thing to note is that the tee I bought for the FP gauge is 3/8", and was too big for the fuel line, so I had to have the fuel lines stretched a bit to get them to fit. I don't know how long I can drive around with the end of the lines stretched like this, so I need to get a new smaller tee for the gauge.

Could the stretched fuel line at the tee have something to do with the fluctuating A/F ratio at idle? Any tips would be helpful.

 

How old are the o2 sensors?

 

I don't know the age of each, but since this problem only arose after installing the Walbro, and finally turning down the FP, I don't think the O2 sensors are a variable.
Heck, even with the FP at 100 I was still idling at 14.7. Only after turning it down did this start. I went back out to the car and it's sounding real rough, and the A/F is really high at idle. I guess I'll try and bump up the FP when it stops snowing.
Or does the ECU just need some time to relearn this stuff?

 

Just leave the battery unplugged tonight.

DF

 

That's unnecessary. All that will do is delay the ECU relearning the short term fuel trims.


OP: The ECU should relearn the new fuel trims pretty quickly. How many driving cycles has it been since you first installed the walbro?

 

Oh, I had the Walbro installed a month ago. Only today did we turn down the FP because I didn't have the gauge installed. Maybe it has to do with the way the tee stretches the fuel lines? Or maybe I just need to bump it up to 48 and see what happens.

I can't imagine what would cause the revs to slowly go between 15 a/f and 20 at idle. Even with 100psi before I still idled at 14.7. 15-20 is crazy, and the car was sputtering. I'm scared to drive it.

 

I smell o2s. Streetz's a/f was behaving the same exact way and it turned out to be fouled out o2s.

 

I would get the proper sizing for the tee but it sounds to me too like an O2 sensor (or both) dead or fouled. For that fuel pressure (42) your AFR's should be stock-like.

Any codes thrown?

 

Since the tee is 3/8", I assume the proper size is either 5/16 or 1/4, right?

What I don't understand is why my AFR would only go crazy after turning down the FP. Like I said, it was at 14.7 (at idle) the entire time I was driving around with 100psi, and only after getting the tee and FP guage installed and turning down the FP did it start acting up.

The thing with the codes is that I have a Maxima ECU in my I30, which has different EVAP stuff, so I'm constantly throwing at least 8 codes due to that. I am throwing an O2 code, but I've had that for at least 6 months. I haven't checked for any new codes recently.

So why would the O2 sensors go bad only after fixing the FP? Why am I running an AFR in the 12s when I go WOT, but it's so funny at idle?

I'm very scared to drive my car in it's current state. At idle the engine sounds rough and vibrates a good deal. I'm tempted to go outside at bump up the FP, but I have no idea what that will solve. Watching my AFR go back and forth between 15-20 is really scary. I'm kinda lost as to what to do....

 

Did he make a post about it? I'm interested to see what happened to him.

 

The fuel lines are 5/16".

What's the AFR doing at partial throttle or cruise.. does it stay around 14.7? Is it only idle that it's going funny? And this is idling after the car is warm and has been driven around a bit right, not on a cold start?

What's the existing O2 code? Have you pulled out the sensors and looked at the tips of them to check for fouling? Sometimes things can be coincidental even though they appear to be caused directly by another event/setup change...

Do you have any kind of scanner to watch the output voltages from the O2's?

 

I wasn't really watching the AFR while cruising, but the car seemed to drive normally until I got home. Yes, it was doing the crazy fluctuations after I got home from a 30 minute drive.

The existing O2 code is bank 1, sensor 2. However, I don't know which sensor that is by looking at it. My mechanic said it was throwing that code because I'm using a Maxima ECU and because of the DE-K swap. I'm not so sure about that however. I haven't checked the tips of any sensors.

I have a Techtom (sp?) scanner, and I think it can monitor voltages, but I haven't checked in a while. What voltages should I look for? Do they change when the car gets warmed up?

With the AFR so lean at idle and the car running so rough, is it safe to drive on, or should I bump up the FP to be safe?

 

Why not bump the FP back to where it was before? At least then you could rule out that possibility.

 

I could, but if running the correct FP is bad for my car, I don't want to know what is good for it.

So why does everybody think it's the O2 sensors? Anyone have a link to Streetz problems?

Assuming it's the O2 sensors, is it safe to drive around without them? The car idles real rough and sounds like azz.

 

there on this page http://forums.maxima.org/showthread....506063&page=10

He describes the problem on post #280, then figures out the problem and pioneers a solution (and stumbles onto a great peice of info on the process) on post #289

 

Ok, by what your saying this sounds like bad o2's. Reason being is, when i was n/a, i had VERY high fuel pressure, because i was advancing timing, but eventually my car started acting up big time, changed to 370 injectors thinking that was the problem, then went turbo. then after a while, i started having same problems you are. while driving, a/f would go to 20's then back to 14's, randomly wether driving or at idle etc.... so after ALOT of investigation, we just unplugged the o2's while car was idleing very rough and lean. as soon as we unpluged o2's a/f went to rich like 13's, and idled perfect. then we pluged the o2's individually and found that one of them is the one that was causing the problem. So i suggest u let car idle, and disconnected both of them. watch your car idle fine. then connect each individually and see which one giving u problems. Since your fuel pressure was pretty high before the afpr, u prob coated your plugs with alot of fuel like i did. so u might have same problem. i also went through 3 maf's thinking it was the problem.

You can safely drive around without o2's being connected, been doing it for about a month. since you run VERY rich and open loop all the time with disconnected plugs, you can just tune any RPM you want, even if its below 3k and at idle and everything. ECU does not know what the o2's are reading so it will not right the corrections you make on ur tuning device. this is how i have been driving for a while, at idle my car is at 14.7 (and with no o2's), it has taken alot of fine tuning but it works. i have mine to be in the 14.7 range upto about 2500rpm, then after that i make it go richer in the 13's because thats where my boost starts to develop. goodluck

EDIT: Forgot to mention that i never got a bad o2 code. dont ask me why lol. so just cuz ur not getting an o2 code dosnt mean its not bad

 

Well I don't have an O2 sensor puller, or really any tools at my disposal to pull the sensors myself. Would it be safe to drive around with them still in and running apparently lean if I can't pull them out? Or maybe I should take advantage of my AAA service and get a tow back to the shop and have my mechanic look at my O2s for me..... Oh wait.....should I just disconnect the O2 sensors at the plugs/clips instead of just pulling them?

Since I probably coated them with all sorts of fuel, is it possible that if I drive around long enough on them that they will fix themselves eventually, or are they pretty much shot at this point? Could that have messed with my wideband at all?

 

no no no, by disconnecting I mean, unplug it at the plugs!, not actually remove the sensor from the ypipe. You can go outside right now and disconnect both o2 plugs and turn on the car and check a/f see how it runs. thats wat i did, i still have the o2's installed on the ypipe and i dont plant to take them out. i just have the plugs disconnected ( i dont care about CEL so it dosnt bother me)

 

He speaks truff!

 

Let me explain something that may help you out here...
1. When the ECU sees the O2 sensors, it takes what they say as gospel- even if they're reading wrong.
2. When O2 sensors get old, their response slows down and eventually stops. Only when it's near completely dead will it show an O2 code. Even when it does show a code, the ECU will still try to use the signal it's getting from it to correct A/F. Thus, it could be getting bad numbers all around and correcting to the wrong thing.

3. By disconnecting the O2 sensors, the ECU goes into a 'failsafe' type mode where it just runs rich all the time in order to prevent engine damage from going too lean.

4. When you were running at 100psi fuel pressure, it was possible the ECU was giving up on trying to correct and just going to factory default values for injector pulse widths. the factory ECU will only adjust about +-10% to factor in minor changes like a poorly spraying injector or changes in fuel composition. After that, the ECU assumes something is wrong and goes into failsafe mode again and just uses a default pulse width.

So when you had your fuel pressure at 100psi, the ECU might have been freaking out and doing just that. so the idle A/F was rock-solid from there. dropping your FP down to 42 is close enough that the ECU will again try to correct things and with the (possibly) bad O2 sensors, the thing is trying to correct to (possibly) bad data.


So, as said above, the first thing to do is to unplug all of your O2 sensors and start over.

 

According to an A32 FSM the ECU tries to correct the mixture back to stoich using the rear o2 sensor by the cat if the front two aren't working properly. Obviously it won't be perfect but it's better than nothing. If the rear o2 isn't working as well, then the ECU switches into open loop full-time.

 

UPDATE

I replaced all 3 O2 sensors, and the car is still doing the same thing. At idle, it sits around 18, then at cruising it goes to 16, and WOT is around 13.

Is it possible that all the excess fuel could have killed my wideband?

I'm also throwing a code for MAF- low air flow, or something like that. Now I KNOW that couldn't be caused from running very rich before, but it makes me think about the electrical cleaner I sprayed on the MAF 4 months ago.

So I'm going to reset the ECU, and see what happens. Maybe the engine just needs to relearn with the working O2s, and I want to see if the MAF code comes back. I'm also going to bump up the FP to about 50, because idling at 18 scares the crap out of me. What are the chances the wideband is now useless due to running so rich before? Keep in mind that before I tunred down the FP it was idling at 14.7, only after turning it down to 42 and installing a fuel tee and FP gauge did my AF start going crazy.....

So, can anyone think of something else that I'm missing?

Edit- While driving through rush hour traffic, I decided I would rev the car to 1200 or so to keep the AF around 16 instead of 18-19. Is this even necessary? How bad is it to idle this lean?

Edit2- I forgot to mention that when the car is warming up and driving around, the AFR was at 14.7 at idle. As soon as it warmed up it went crazy again.

 

So in open loop mode, A/F is okay... At that point, the ECU is only going by the MAF voltage to determine how much fuel to spray.
once the thing warms up and goes into closed loop mode- reading from the MAF and o2 sensors, it's now going funky.

It's possible, but unlikely the WBO2 was damaged from the rich condition. how old is the WBO2 though? I know the WB sensors only have a short lifespan. they're getting better, but I know they don't last terribly long.

If you know of someone else that's got one, you may try swapping out the sensor with another one and see if it changes your numbers.
I have a feeling that's what you're really seeing though. :shrug:

 

The wideband is about a year old, and I don't know anybody around here with one I can swap....so you think the wideband is the culprit here?

How bad is it to have your idle up at 18? Maybe I should find someone else with a good MAF and see what happens when I swap it in.

 

I just thought of something...maybe I should reset the wideband. Any other ideas?

 

I just thought of something....if the wideband is reading 14.7 at idle during open loop (only reading MAF), doesn't that mean the wideband is reading correctly? And if it's reading 14.7 in open loop, wouldn't that indicate that the MAF is functioning properly?

I bumped up the FP to 50 and reset the ECU and drove around for a minute, but didn't get out of open loop. The car sounds fine and seems to drive fine, but if what I'm thinking is correct, the wideband IS reading correctly, and I AM running really lean. Since I replaced all O2 sensors, and the MAF seems to be working, what else could be causing this?

 

So does anybody agree or disagree with this? I'm confused....I think I'm gonna replace my spark plugs....

 

UPDATE:
Well I let the car sit for a few days after bumping up the FP to 50 and resetting the ECU. Today I went for a drive, and the AFR at idle seemed to be fixed. The only unsettling thing is that if I'm decelerating in a gear (off throttle), the AFR is pegged at 20. Is this normal when I'm in gear but off throttle?

Second, I checked my FP while the car was on, and it had gone from 50 down to about 40 psi, and I bumped it back up to 45. Now IIRC, I'm using a Nismo AFPR, which I've heard is a reliable unit. But if my FP is going to drop like this without warning, I could see this causing problems. Has this happened to anybody else? What, besides a faulty AFPR, could cause the FP to drop like that? Could my incorrect fuel tee fitting have anything to do with it?

BTW- What is the correct FP for our cars? 44 or 34?

 

the wideband i had did the same when i let off in my old 2k1 auto. it was obviously still in gear but went right back to 14.7 give or take a little when back on partial throttle. i used a cheap megan fpr which i would notice the fp would change very small amounts from time to time. mine was set at 3 bar (stock pressure for 4th gen & 5th gen 3.0) with zero correction on my vafc2. when i wanted some indirect timing advance, i would bump it 3.5 bar (stock for 5.5 gen) and back the additional fuel out with the vafc2. i dont think the tee has much to do with it and heres my reasoning. i used a mustang gt walbro because it less expensive and had a larger inlet. the increase in the inlet did me no harm. maybe that last part is stretching but it makes sense.

 

when you're decelerating off-throttle, your A/F doesn't matter. in fact you want to be burning ZERO fuel- otherwise the engine would be making power while you're trying to slow down. make sense?

 

Sounds good

I've been keeping an eye on my FP lately...here's what I've figured out. Right after I start the car, the FP has ranged from 42 all the way up to 52. One thing that has stayed consistent is that FP usually drops 4-5 PSI from the start of a drive to when I park the car. Is this due to running in open loop when I start the car, or should FP remain constant from the second I start the car to when I turn it off?

 

The ECU never actually shuts off fuel flow completely. The injectors are still firing, but at a very low pulse width (usually around 0.6-1.x ms) and the ignition timing goes down to zero advance. Same at the fuel cut as far as IPW is concerned. OT, but just wanted to clarify.

 

Thanks for the info. Any thoughts on the drop in FP during every drive?

 

UPDATE

The car drives normally, except more and more often the AFR at idle will rise to 18 or so. When cruising, it will stay around 14.7, and sometimes at idle it will stay at 14.7, but more and more often it will raise to 18. When it does this, the car starts to vibrate and sounds like it's about to stall. AFR at WOT is in the 11's, with FP around 45. With the Walbro, should FP be 44, or is that only for people with the stock fuel pump? I get the feeling the car would run around a 12.5 AFR at abour 40 psi FP. Thoughts?

The FP still drops during every drive, but I can only assume this happens because FP gets bumped up during open loop. Is this normal?

So now my main worry is the erratic AFR at idle. Would could cause the AFR to be normal sometimes, but go crazy other times? I still haven't replaced the fuel tee for the FP gauge, but I'm skeptical that it would cause a problem like this.