What would cause my idle and cruise AFR's to richen up over time while driving?

Here is the skinny;

During and immediately after tuning and a quick test drive idle and cruise AFR's are spot on, but during the 3 hour drive home from my tuner they start to gradually richen up and it looks like the ecu tries to compensate to hit target AFR's, but never quite gets there bouncing between 13.5 - 14.2 never getting back to 14.7ish. Same thing goes for idle. Seems to be a little worse on bank one. Confirmed with OEM widebands via CIPHER, ROM editor (logging and tracing) and along with my aftermarket wideband gauges.

Here is the kicker... If I clear the learned fuel settings with CIPHER they immediately go back to 14.7ish for both idle and cruise, but the cycle begins once I start putting miles on. Any ideas? Something simple?

If you could please get back with me I as always would greatly appreciate it.

2006 G35, Vortech, ID725'S, GT MAF, Walbro, UpRev Tuner version, MREV2/spacer, full exhaust, etc...

 

From what I gather I could either have an exhaust leak, or that the target and compensation maps aren't close enough and is fighting one another. Just want it sorted out seeing how I am FI now.

Have a buddy looking at my maps. They should be good...

 

My buddy said the tune looks great and that the target and compensation maps are fine. Making a makeshift leak detector out of a party smoke machine, spare hose and bits and pieces around the garage.. Lol! We will see...

Have you seen what a smoke leak detector costs? Its ridiculous!

 

Performed audible, visual soot and smoke leak tests both hot and cold to no avail... Did not see any cracks. soot or smoke. Also smoked the plenum as well... Nothing!

There was a member on 350z pretty much in the same boat that all he could do was just keep clearing the learned fuel settings via CIPHER to get things back to normal just as I am doing.

If left alone, after a while the SES will come on and P2A00 will be present and if left longer it will be accompanied by its ba$tard brother P2A03.

Hours upon hours of researching numerous forums, emails to tuners and conversations with friends tend to leave me empty handed and just plant more things in my head and I feel like I am grasping at straws as most seem to do with this situation.

There was a guy that had all his gaskets replaced, 2 fuel injectors, MAF along with all o2 sensors both primaries and secondaries and is still getting the code(s).

It has to be related to my STILLEN headers install 2 years ago because that's when the codes immediately appeared... I honestly believe with my first NA tune they simply disabled the codes thus explaining why I never got a SES light until now after the FI tune.

Some suggest the rear o2 sensors are the problem, grounding the exhaust, or not using the berk extensions and welding a bung in putting them directly in the exhaust stream...

So many threads on these codes not necessarily the AFR issue, but I do now have the tools to monitor them as before I did not, so maybe I am just seeing in real time what is actually happening.

I will keep on keeping on and see what I can find.

 

shot in the dark....

Have you pulled the AFR sensor to see if there is any contamination on it?

 

Yes sir. I've inspected, swapped, and eventually replaced them with new oem ones. They have less than 4k on them. I ran my Berks and Borla with the oem manifolds for the longest time with no issues until the day I had my local Infiniti dealership install my headers. That was back in 2011. I've been on 3 deployments since then. Had the car a little over 3 years and havent put more than 8k on it. Lol!

Same 2 codes...

 

since the AFR sensor is a "current" type device, I would check the various connections for water, corrosion etc. Any resistance in the circuit can change the amount of milliamps the unit transmits, and we are talking about very little current (0-50ma). The only other thing I can think of is a drop in over all voltage during the trip. Do you have a volt meter anywhere on the car?

 

Sure do. 14.3 - 14.4v entire way. All connection points are clean of derbies and have been clean with contact cleaner as well. My aftermarket wide bands mirror my oem widebands AFR's within +/- .1 as well.

 

well I can sure see why you're stumped..... I am too.

 

Haha! Tell me about it... Appreciate the help though. I'll keep plugging away. Tomorrow I'll re-torque all that I can.

I have been thinking that maybe the MAF is getting too hot?... They are unwrapped stainless headers... Might put a sleeve on it. Just thinking...

 

The only way to confirm that the AFR is working is to measure the current while driving. If you see a change in current while in a steady state, you know that it's the sensor. You would need a good VOM and some rigging. What would be really nice would be a VOM that you could hook up to a laptop and record the current over time and plot it.

 

I completely disabled my rear o2's to rule out any conflict between the primary and secondaries. (I know the codes are for the primaries) Just a shot in the dark. Long story short it was NOT a fix.

Looking at live data, o2 sensor voltage is correct in regards to my research. Like I said it most likely is a exhaust leak that I will have to hunt down when I get the time.

Here are some fuel tables ran through a program created from a guy over at my350 with some logs I supplied him.

 

Ever find a solution definitive solution? I have had my tuner check for leaks, cleaned MAF, replaced Bank 1 Senor 1 (I only am throwing P2A00), did throttle relearn procedure and SES still comes on every 100-700 miles. Mods are below. I am at a loss for what it could be at this point. I disconnect the battery and my g runs like a bat out of hell for ~200 miles and then code comes on and it runs like **** (worse mileage, doesn't pull as hard). Rinse and repeat.

06 6MT <40,000 miles as of this post
MD 5/16 spacer
MREV2
Z-tube
Berk HFC
HKS catback exhaust
Uprev Dyno Tune after all parts installed

 

Unfortunately, no.

I'm still in the same boat. Getting about 230 miles per tank. Clear codes, less than 50 miles their back. Now getting a high idle code as well.

I am about to remove and replace the entire intake plenum (MREV2 spacer, etc), Stillen headers and OEM throttle body with: a Cosworth plenum w/ NWP throttle body, PPE longtubes w/ new O2's and Ill clean the MAF.

I f***ing hope this fixes the issue.

So you do not have headers. Once I put mine on, that when the codes started popping up left and right. Both NA and now going FI...

The dealership, myself and my tuner looked for leaks as well. I have no clue. Its nuts. So, frustrating to not find an answer. TRUST ME!

 

Was there some kind of coating on the headers that might be causing electrical resistance? Make sure the threaded bung for the AF sensor doesn't have any ceramic coating or anything on it, apply kopper-kote anti-seize when you install the AF sensor because that stuff is electrically conductive, also try adding a supplementary ground onto the header-cat bolts just to rule out an electrical issue.