So my afr is bouncing all over the place at idle and cruise. I have tons of logs and checked. When i'm in boost and open loop my afr is solid on the money. I only have problems when i'm in closed loop. I replaced the upstream o2 sensors hoping that they were the cause of the lag in my afr. It can bounce from the 13's to 16's while just idling.

Every now and then it will bounce up to 17 and the car will hesitate. No codes thrown. I'm thinking it's the MAF sensor (sense that controls closed loop also). These beasts are expensive so i don't want to buy something else that i don't need.

Does anyone have one i can paypal you to borrow and see if that's my problem? I would greatly appreciate not having to spend another 250$ on something i don't need.

thanks guys!

 

i would be open to someone testing my maf also. i just need to know if it's dead. lol

 

Unless your 350z has a wideband o2 sensor, the AFR will appear to bounce back and forth most of the time, this is normal. I had a highly tuned Eclipse GST before and the AFR gauge reading would bounce back and forth unless under throttle. Sorry I don't have a spare MAF, but you may start by cleaning the MAF and downloading a shop manual that should give procedure for testing the MAF with a multimeter.

 

i've cleaned it multiple times with no results. It has been kept clean since my vortech install anyways so i didn't think that was the issue.

I have innovate wideband, aux box, and LM-2 datalogger. Wideband isn't supposed to bounce from 13's to 16's. That's a huge a/f swing and it is something that just started happening in the last few weeks. I never had that problem before so something has obviously changed.

I'll try to get a shop manual and see if there are voltages or resistances i can check on the maf.

 

You're right, with a wideband you shouldn't be seeing that much of a swing in AFRs. I'm assuming with all of your datalogging equipment you can read pending SES codes and there aren't any? It sounds like there may be un-metered air entering the system... but you would think there would be a boost leak if the issue is downstream of the turbo. Have you tried posting in the forced induction section?

 

What EMS? A misfire will cause transient rich conditions. Do you have Cipher? You can log MAF output and see if it is related to AFR. Rather than borrowing a MAF, try to find someone with Cipher that can help you datalog the events...

 

haven't tried posting yet. I've spoken with a few guys that know their stuff on this matter and they don't have an answer.

I have no codes, i've reset the ecu and did all the learning procedures.

It's a supercharger so i'm not sure what would matter downstream of anything. I was thinking unmetered air also but my boost hasn't changed, i've pulled everything off and re-tightened all connections and checked vacuum lines.

When WOT in open loop my afr is solid and exactly what it used to be at. It doesn't bounce or vary at all. It should still have problems in open loop if there was extra air coming into the system or a leak wouldn't it?

 

It's the wonderful split second box. ya ya i know it sucks but that's all i have right now while i'm saving up for a haltech. The only issue is i'm worried that something else is burnt out so i need to replace it before replacing my ems. Medical school makes me a broke *** nowadays so my car fund has dropped a lot.

My LM-2 datalogs anything obdII like the cipher. I have logs of my MAF if you would like to see them. I really don't know if it's functioning or not by looking at it because i've never logged the MAF when the car was running properly.

edit: added logs from my LM-2. it's in .log file but i can save as .dif if anyone needs it. You can see the purple line is wildly swinging (afr) and at the very bottom is the maf. another edit...it won't let me post it so if anyone wants to see it i can email it. just pm me.

i guess if i'm getting a misfire it is too small to throw a code? so i should start putting all wiring connections and see if i'm getting a misfire somewhere?

 

is your idle bouncing as well?

unless your afr is hangin at either extreme for a few seconds or your idle is jumping a few hundred rpm, i wouldnt even worry about it. with the big temp changes lately, your stock ecu takes more to nail its preset values.

 

that makes me feel a little better but not 100%.

ya, the bouncing isn't as much that concerns me as sometimes when it bounces into the 16-17 range the car kind of bogs at idle but only for a quick second. If i'm driving at cruise and this blip occurs then i can feel the car lurch. It feels like a dead spot when i'm driving.

I've logged all my fuel trims and they are all close to 0 when you average them out with no big swings. There aren't any places that look like the trims are maxed and causing the car to go crazy.

Also, if i'm driving and i push the clutch in to coast to a stop the afr drops into the 11's and 12's.

maybe it's the split second EMS. someone should donate a haltech to me so i can test to see if that's the issue

 

the drop in AFR upon decel is normal.

mine constantly hunts between high 13s and low 15s, esp when its cold. those microsecond readings dont mean anything, esp if its not long enough to make your idle erractic. You could feel that.

 

so what about the times wheni can feel a lurch at cruise or when it blips high afr and idles different for a split second?

is that still normal? my idle for the most part is ok. If i sit and let the car idle for 5 minutes or so i would say the little lurch/bog from lean happens a few times (in the 5 minute period). Maybe i'm crazy and didn't notice it before?

I feel better knowing i'm not the only one though. I don't want to have small issues when i start switching things out and dropping more cash in the car.

str8, do you have logworks or anything to view a log file? i can show you the logs and then you could see if that is a normal afr swing.

 

I have logworks, but what you describe is not normal. It could be anything from an exhaust leak, to TB malfunction, to vacuum leak, to miswiring or loose harness, to faulty injector, or fouled spark plug. Are your battery posts clean? (no acid grunge/powder?)

 

battery is new as of a few months ago. It stays on a battery tender in the garage too so it always has a good charge if i leave it for more than overnight.

rcdash, i'm going to pm you for your email so i can send you the log

 

Binder,

did you ever find what caused the jumping A/F idle problem and fix it? I'm experiencing something similar along with misfires @ stoich a/f's during idle as well as fluctuating A/F during idle.

 

This was in 2009 when i had osiris flash and a supercharger. My entire setup is wildly different.

I'm pretty sure it was just my tune but since it was 1 1/2 years ago and 3 setups since then i can't really recall.