rock_man

Hello folks,

I bought my 2004 Z06 a few years ago. It came with a Vararam intake. I replace that intake with a dual cone type last year. Today, I replaced the dual cone intake with the stock C5 Z06 air box and new WIX air filter. The car is now showing the CEL with p0172 and p0175 at the same time viewed with the DIC. I replaced / changed no other parts at this time. AFAIK, the car was not throwing these codes, nor a CEL prior to the stock air box install today. I tried pulling fuses 16 and 23 to force a fuel curve re-learn (found this suggestion in a forum search), but the codes are still showing in the DIC, but no CEL yet. Any ideas?

Thank you

Documented history and summary of this issue:

1. Car was purchased in October 2014 with the Vararam. No H or C p0172 and p0175 codes present. No parts or tuning documentation.
2. Last year in 2017, the Vararam was removed and replaced with a dual cone-type of intake/filter. No H or C p0172 and p0175 codes present.
3. April 2018, the dual-cone intake/filters were replaced with the OE Z06 air box and Wix filter. p0172 and p0175 H and C codes present with CEL.
4. April 2018, I performed the re-learn procedure FWIW (Key On Engine Off, removed fuses 16 and 23, Key Off, replace fuses, start car and run engine at idle for 15 minutes, then test drive it for 20+ minutes.) After clearing the PCM comm codes, no other codes showed initially, but the CEL pops again with p0172 and p0175 as C and H.
5. April 2018, triple-check everything, clean the MAF again, re-assemble the intake up to the throttle body and check for air leaks. I'll drive the car, along with some data logging, for a week see how it goes.

grantv

Did you have to move the location of the MAF?
Thinking either just moving it could cause that, maybe it's not air tight, or the car was tuned for the Vararam and needs to be retuned.

rock_man

Hi, no the MAF never moved and is flowing the in correct direction. All the connections are tight. But you bring up a good point, thank you. The car may have previously been tuned, but I have no records of it. I didn't know the Vararam requires an engine tune?

rock_man

Thank you for the reply. I was thinking the computer needs more time to re-learn the intake, or I need a re-tune. Currently, p0172 and p0175 are both showing H and C. Fortunately, it is a rich condition. It could be worse.

Gordy M

More than likely the car was tuned when you had the veraram. Since it was pulling cooler ambient air (more dense) it needed more fuel to run optimally. With the dual cone and stock cleaners, it is now getting warmer (up to 170F) air (less dense) and setting the rich codes. It takes 50 ignition cycles for the PCM to retune and even then you have no idea if it is running rich or lean, I would either get it returned or at a minimum put the original tune back in. When you throw the 172/175 codes your PCM if showing the Long term fuel trims are more than 25% off.

rock_man

Hi and thank you for the reply. I wasn't aware the Vararam or the dual cones needed a tune. Some basic data logging at idle shows Long Term Fuel Trims at -18% both banks, with Short Term Fuel Trims bouncing in single digits around zero. LTFTs move towards zero when the accelerator is pressed. I haven't performed any detailed logging.

Can I reset the fuel trims with a scan tool, or just wait for the 'puter to adjust?

I was thinking to double-check my install and drive it to see if the 'puter eventually sorts itself out. If the rich condition persists, I'll start looking for a local Corvette tuner.

Cheers

Gordy M

If you scan tool is bi-directional you can reset the LTFT and then take it on a 20 minute drive for the PCM to relearn. If they still are above +/- 5 then you definitely need a return. The problem with he dual cone is it uses heated engine air but a larger diameter intake to the MAF. This actually causes the velocity of the air going to the TB to slow down and causes the rich condition.

Bill Curlee

I would check the air ducting between the MAF and the TB for air leaks. I would also try to clean the MAF. Then see what everything is reading and go from there.

Bill

Bill Curlee

Sometimes people tighten the Air Bridge clamps too tight and it collapses the air bridge and that lets in un-metered air.

rock_man

Hi folks, thank you very much for your assistance! Allow me to re-state the issue and history so I can document this correctly and help the Corvette collective understand.

1. Car was purchased in October 2014 with the Vararam. No H or C p0172 and p0175 codes present.
2. Last year, the Vararam was removed and replaced with a dual cone-type of intake/filter. No H or C p0172 and p0175 codes present.
3. This past weekend, the dual-cone intake/filters were replaced with the OE Z06 air box and Wix filter. p0172 and p0175 H and C codes present with CEL.
4. Yesterday I performed the re-learn procedure FWIW (Key On Engine Off, removed fuses 16 and 23, Key Off, replace fuses, start car and run engine at idle for 15 minutes, then test drive it for 20+ minutes.) After clearing the PCM comm codes, no other codes showed initially, but the CEL pops again with p0172 and p0175 as C and H.

To do this week: I will triple-check everything, clean the MAF again, re-assemble the intake up to the throttle body and check for air leaks. I'll drive the car, along with some data logging, for a week see how it goes. I'll post photos of the setup when I have the chance.

I used CRC electrical contact cleaner on the MAF sensors. Is there something else I could be using?

Bill Curlee

I use NON CLORINATED Brake Parts Cleaner BUT,,, some will cringe at me using that. Never had an issue. Use MAF cleaner to be absolutely safe!

rock_man

Update!

I removed the MAF, sprayed the elements with CRC MAF cleaner and reinstalled. Cleared codes. Test drove the car yesterday and today. I noticed immediately the car performs more smoother and pulls harder. So far, so good! Today, it threw a MIL with code p0101 H (MAF Performance). The rich codes p0172 and p0175 have not reappeared. I feel a very slight stumbling ever so often at part throttle. I have also noticed the intake behind the throttle body is wet with oil.

I am thinking:
1 - MAF elements are still dirty. I will remove and carefully re-clean elements using a q-tip soaked in MAF cleaner.
2 - Oil from the PCV system is fouling the MAF. I already have an Elite Engineering oil catch can on order to install.
3 - MAF is damaged and needs to be replaced.

I'll perform #1 and #2 before replacing the MAF, but if there is anything else to check that I have missed, please let me know.

Thank you!

rock_man

Update!

It's been a few days since I removed, cleaned and reinstalled the MAF again. I made sure everything was tight - no air leaks. Reset PCM (pull/replace fuses 16 & 23) Cleared codes and drove the car for a few days. Also data logged with HPTuners. No return of any codes at this time. Car runs smooth and strong! I consider this solved.