binder

iTrader: (8)

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.


i posted this in another area with some comments if you want to follow up on them here:

https://my350z.com/forum/maintenance...ld-borrow.html

opinions or advice welcomed.

marra23

iTrader: (8)

your fuel pressure solid at idle?

athenG

iTrader: (2)

Clean MAF/TB and do the idle reset/relearn.

CeBrwn5454

iTrader: (2)

BUMP for answers.

binder

iTrader: (8)

well, according to the sensor and logs it is solid. I will be switching over to a RFS so i can lower the pressure down to see if that helps with my 440cc injectors. Again, i'm trying to make sure everything is running properly before upgrading things.

maf cleaned with maf cleaner, air filter cleaned, all intake piping checked for leaks. ecu reset and all the closed relearn, idle relearn stuff done too. Still no change.

I've tried making adjustments to the closed loop tuning to see if that does anything but it doesn't. All it does is screw up my fuel trims.

athenG

iTrader: (2)

is there a way you can borrow a MAF and TB to troubleshoot? Your TB maybe taking a crap on you.

binder

iTrader: (8)

oh suck, i never thought about the thottle body. That sucks. It's annoying that i do'nt have any error codes.

I'm trying to get ahold of one to test but there aren't many 350z/g35 owners around here. The few i see driving around are definitely not "tuners" that would take parts off their cars. I have 1 friend with one but he hasn't gotten back to me yet on borrowing anything off his car.

1GR8350Z

iTrader: (1)

My S13 had identical symptoms with even more erratic jumps in A/F and it turned out to be a bad injector. We went through all the same steps with the TB, fuel pressure and temp corrections but a new set of 740's fixed it.

athenG

iTrader: (2)

/\ Did you also have an erratic idle?

binder

iTrader: (8)

interesting.

how do i test injectors or who tests injectors (and the cost?)?

i might throw my stock injectors back in and see if it runs ok when i stay out of boost. stock injectors should work fine for no boost.

when the injector was going bad did you have problems when in open loop? my open loops is great and spot on which is why i'm confused on the issue.

1GR8350Z

iTrader: (1)

Yes it was in open loop on Power FC. Not sure how to test them but we took a shot in the dark because that was about all that was left to try. Just happened to have a spare set on a blown engine. I'm far from an expert and am still learning but the symptom just sounded very familiar.

binder

iTrader: (8)

hmm...well my open loop is spot on so the issue is only isolated to the closed loop portion. That's what makes me think it was a feedback issue from the engine when adjusting the afr for closed loop.

athenG

iTrader: (2)

If your problem is just A/F then I may look into the injector but if you also have idle problem then I would make sure the TB is ok before you get new injector. You are fine in Open Loop so your injector should be fine. If it is shot/clogged injector then you should also have problem in open loop. I had the same issue and my problem was a vacuum leak in my catch can. You may may have a vacuum leak for that matter.. Vacuum leak is a b1tch to find, it took me 3 months to find that leak

Edit:

Ok, I just re-read your post and your problem is just A/F bouncing but your idle is fine. I had the same issue and in my case it was a vacuum leak in my catch can. I was fine during cruising though because of the 02 feedback. I would send the injector for testing just to be safe. Make sure you have no leak on your exhaust close to your Wideband..

binder

iTrader: (8)

hmmm, i'm going to swap injectors to see if that's the issue. It might be a misfire but i'm not sure what's caused by it. Maybe a leaky injector?

I do'nt think i have any leaks in my exhaust. It hasn't been taken apart or abused since i installed the headers/test pipes with my system and just all of a sudden i'm having this issue. would it swing down into a low afr if it had an air leak?

also, for this to affect closed loop i was just thinking it would have to be at the header/head since it would be my upstream o2 sensors that control the afr.

how the crap do i test the headers to see if they are sealing? it's a tiny space up in there. i haven't had any changes in noise.

djamps

iTrader: (1)

What EMS? My gut feeling is that your closed loop trims and/or scaling are way off.

binder

iTrader: (8)

split second box.


i just retuned it for the colder weather (because it was acting funny) and that didn't fix it.

With my logs idling and driving all around town my closed loop fuel trims don't go past single digits either + or - of 0. That's what it was tuned like this summer and it didn't do this. I thought fuel trims until i did logs and found they are all very close to 0.

Resmarted

iTrader: (2)

if you have an exhaust side leak, you would know from a good visual inspection: high pressure exhaust leaks leave a jet/line looking black line, its pretty neat looking actually.
but my bet would be on injectors. MAF is possible, but tb just doesn't seem very likely on such a new car.
in for the knowlade!

CeBrwn5454

iTrader: (2)

OP,

Your problem sounds a good bit like what my car was doing a week ago or so. You commented in my thread...it was about compressor surging and such.

I've sent my blower to 928 and should have it back early this week...if that does not fix the issue I'll be in the same boat as you.

Best of luck.

P.S. Would an injector be ruled out if the only time I feel a "problem" is during a rolling deceleration from 30+mph (meaning I am giving it no gas...mph estimate) and idle? When are you in "closed loop"?

binder

iTrader: (8)

I'm thinking injectors could be an issue also. It's cold as hell today but i'm hoping to swap out the injectors with stock injectors and see if the problem changes.

I'm going to take the vortech belt off first and see if that changes also. That will verify if it's the same problem as CeBrwn.

CeBrwn5454

iTrader: (2)

In for results!!