Hey everyone I've posted a few threads about changing o2 sensors recently due to crappy gas mileage and upstream sensor codes given. But when expecting my engine right now after driving and feeling the car running a bit more worse than before I heard this noise that I don't recall hearing before..here's a video and listen very closely there's a hissing noise. Now I've played with the engine a lot before and don't remember this noise at all so i remembered reading the codes and it says if it's not the the o2 sensors bad then a vacuum leak is the possible culprit. Now can someone she's light on this annoying problem I've had for awhile now

http://youtu.be/im_Mkb1t1S4

View My Video

 

Bump for help

 

Couldn't really hear a hissing noise, but I had a nasty vacuum leak at my brake booster. It caused crappy gas mileage, extreme lean conditions, and I thought it was my O2 sensor as well.

You can try spraying carb cleaner or an UNLIT propane torch around those areas and see if the engine revs up a little. I built my own smoke machine and I put a DIY here and that's how I tracked it down to my brake booster. I also used SeaFoam to check for exhaust leaks.

I'd check your intake, throttle body gasket, oil cap cover, plenum, and PCV hoses.

Do you have access to an ODB scanner? I use Torque along with a PLX Kiwi I think and I have Consult 3 clone, I pull out when I need to do some real troubleshooting. You can also buy a vacuum gauge at Harbor Freight for like 20 bucks. Hook it up to the small port on the plenum and see if the vacuum drops up and down.

 

Yea I have the osiris tune with the cipher which gave me the codes for the two upstream sensors. And I used carb cleaner with no luck and seafoam too! That's why I'm at a lost now..didn't know about the vacuum tool have to
Look that up sounds a bit easier to find with that

 

I think it should be steady at 19-22hg, while at idle. Mine would stay at 19, jump to 22, and then stay at 19. It would do this every few seconds. Have you done any work recently when this started?

 

Try reading your Air to Fuel ratios as well.

 

Yea my A/F ratios are a bit off according to Seymour(he's the best, he's been helping me a lot) on this site which I bought osiris from. This is a quote he sent me recently "Its idling really rich... like I said before it should be around 14.7, you're down in the 13's."

 

What code are you getting? Try unplugging the mat sensor at idle and see how it runs. You'll get a bunch of lights, but it puts the car in a default rich mode. You're taking these readings when the car is in closed loop mode right? You could have a dirty or faulty injector also, if its running rich.

 

It's both sensors upstream on both sides. Also yes it was closed loop. When you said "mat" you meant the "maf" on the Intake right?

 

Yes I meant MAF, sorry I was typing from my phone and didn't notice the typo. Are you stock or do you have HFC? If so do you have spacers on your O2 sensors?

Turn the car on and get it to operating temperature, unplug the MAF, and then monitor the fuel trims. It "should" get down to -25% this is the default rich condition if it's not that number then you probably have a vacuum leak, but a smoke test is the best method to see if you have one. I've also heard from an Infiniti tech Bosch sensors aren't good in our cars.

Buy some MAF Cleaner from an auto store and try cleaning your MAF also.

Any other mods?

*I have a set of 4 used OEM A/F and O2 sensors I can sell you if you want them. They're used and I paid about 60 bucks. I also have a brand new MAF I bought for about 300 that I can let go for a little less if you end up needing any of those parts.

 

I will keep you in mind for the parts! But yea I do have Berk hi flo cats on my car, but didn't know there was a need for a spacer with these is there? I know test pipes for sure.

 

I'm pretty sure you need spacers for the rear O2 sensors. They check to make sure the upstream are giving the correct A/F ratio. Since, you are getting the code for both banks, I want to say that's probably part of your problem. Try that first and see if it fixes your problem and after you do that disconnect the battery and hold the terminals together for like 10 seconds.

 

Ok here's update: I uninstalled my plenum spacer and realized some of the bolts were loose. I reinstalled tightening down everything and the noise went away! But the CEL is still on and the car is still idling weird also while it's doing this the engine starts to shake slightly...and codes are still there

 

Did you reset the ECU or disconnect the battery afterwards? What is the RPM it idles at? I just think it would be weird for both A/F sensors to go bad at once. You replaced the upstream sensors right? Are you sure they're seated properly and not causing any leaks? Are they OEM or not?

 

I haven't replaced the upstreams yet I really don't want to spend that cash if I don't have too! Lol also I don't know where to find good oem ones at that yet. But I will do the ecu reset now I can't believe I forgot to do that