I had my new '04 Z06 for a week now, and brought it in to a dealership because I had a "Check Engine" light on yesterday. The mechanic says the engine is too lean on "both sides" (?).

I also did get a few mods done yesterday (CAGS disabled by specially-made resistor, Borla Stinger cat-back, Halltech air filter) with no reprogramming (I'm happy I didn't). But the mechanic thinks this is unrelated as the MAF sensor should compensate and provide appropriate Fuel/Air mixture for the slightly better breathing.

During the past week (car with no mods) I felt the car's pull (seat-of-the-pants feel) on freeway on-ramps like a wave (as if torque changed significantly with RPM) and about 10 time (mainly with cold engine) shifting from 2nd to 3rd under full acceleration, the car would bog down in 3rd for about a second or two before returning to full power.

More diagnostic will be done Monday morning at the dealership by the mechanic. He is suspecting something wrong with fuel delivery pressure.

Can't wait to get my car back :( . I never loved a car like this one.

Did anyone else have a similar experience ?

I will post back here when the source of the problem is found. I hope it's the car and not the driver. :D


[Modified by jerome, 4:36 PM 12/7/2003]

 

This is an issue with the airbox. Put the stock airbox back on and the problem will disappear. You may be able to fix the issue with the aftermarket airbox, but putting the stock box back on is a quick solution.

 

This is exactly why I haven't put any mods on my Z06 as of yet. I keep hearing stories like this one!

 

You probably have undetected air sneaking by the MAF sensor and the PCM's initially delivered fuel mixture does not have enough fuel to get stoich. The O2 sensors report the lean mixture and the PCM attempts to compensate with extra fuel via fuel trims.

Your PCM is applying the maximum fuel trim correction and the O2 sensors still reported lean. You got a DTC code which turns on the Service Engine Light.

When I said reinstall the stock airbox I meant to totally remove the aftermarket box and reinstall the stock airbox and airfilter. This will certainly address the issue. You may have an airleak somewhere in your aftermarket setup. You could try to look for any airleaks in the aftermarket airbox because they will cause this problem. Many people (including myself) run with aftermarket airboxes and do not get lean codes.

 

Jerome. Did the dealer replace your MAP sensor?

Your MAP code was on the PCM before I installed the TRAP

I didn't program your car, due to the two existing PCM10 codes that showed up. The MAP (manifold absolute pressure sensor) works hand and hand with the MAF in determining airflow parameters. My suggestion was to have the dealer deal with those before we program.

Codes are rare, but happen more often with the Z06 due to the laminar airflow honeycomb screen being removed from the factory.

I have found that the stock 2002 to 2003 Z06 to be +8 to +10 on the Long Term Fuel Trims stock. Adding our TRAP, adds more airflow, but the problem is due to misreading the new airflow, which creates a larger correction between the O2 sensors and the MAF metering.

The car is not running lean. Period. The codes indicate the amount of fuel that the O2s have had to add to retrim the car to 14.684:1. That's all.

As soon as you get the other codes fixed, which may be part of the problem since one code was the MAP sensor frequency, we'll program it and correct the MAF metering problem. Simple deal.

We will also add some more power.

Jim





[Modified by Jim Hall, 9:50 AM 12/8/2003]

 

Just talked with the dealer. They told me that the stock airbox and MAF combo shows a +10% LTFT in both banks and 18% with the TRAP.

That is within the 24% threshold provided by the PCM before tripping a code.

The mechanic told me he sees MAFs vary as much as 10% which in this case is the reason for the code. The problem is, it is not possible to go through a stack of MAFs to find one that meters closer to zero.
the solution is to program the LTFTs to bring the baseline closer to zero.

Give me a call.

Jim

 

As I mentioned, it is not unusual for the Z06 screenless MAF to miss some of the airflow.

As an example, our LS1 with the stock screened MAF ran at +10% unmetered air with our TRAP. When we dynoed it with the screen in place and no programming, it picked up 20.1 RWHP/22 ft. lbs torque.

I then installed a 2003 Z06 MAF (no screen) and lost major power due to spark knock from 15:1 a/f ratio.

At that time I did not have a programmer with me, so I went back to the stock MAF.

Today I checked the LTFs with the TECH 2 again, and found them at 8 to 10%. I installed the Z06 MAF and the TECH 2 showed 18 to 20%, getting pretty close to the code margin.

In 10 minutes I reprogrammed the MAF tables and brought the LTFTs down to 0.

If anyone is having problems with codes on their Z06, give me a call. I will reprogram your MAF tables to correct this FREE.

Full programming is $250.00 at Halltech when we install the TRAP at the same time.

Jim

 

In my first message I said : I now know what is going on...

About "the car's pull (seat-of-the-pants feel) on freeway on-ramps like a wave (as if torque changed significantly with RPM)" :
It is because of the freeway on-ramp near where I live and the new car power/suspension. This particular on-ramp is not totally flat and has dips that I only really notice now with this new car because I can go much faster on it and the combination of dips, increased speed and car acceleration gives me this new feeling. I don't get that with the other freeway on-ramps I used in this past week.

About "about 10 time (mainly with cold engine) shifting from 2nd to 3rd under full acceleration, the car would bog down in 3rd for about a second or two before returning to full power" :
I is because I was (still am) new to this car and have not perfected my 2-3 shift as well as the easier (just pull) 1-2 or 3-4 shifts. Engine RPM has enough time to get off from ideal setting for 3 gear after hunting for it (I'm trying to be nice to the car) and I get wheel spin, probably from over-revving it and the TCS (Traction Control System) kicks in.
It was raining yesterday for the first time and I got the same engine power cuts when the rear wheel would start spinning in 1 or 2nd gear due to the low traction.
I am told I can disable this by setting the car in "competition" mode my holding down the "active handling" button for a while, retaining active handling but disabling the TCS.
It made sense that this happened most when the engine was cold, because that is when the tires are too (less grip).

About the "Check Engine light" :
Yes it was because of the installation of the TRAP. Because it was installed without re-calibrating the MAF sensor. So the LT FT (long-term Fuel Trim) got up to 18-20 (instead of 10 with stock airbox) close to the limit of 24, in which case a small variation could trigger a code that will have the "Check Engine" light turn on.
Yesterday, Jim Hall worked his magic and re-calibrated the MAF sensor, so it reports proper airflow that match what the Oxygen sensor hopes to see at its end, and no LT FT correction is required. Problem solved.


[Modified by jerome, 12:20 AM 12/13/2003]

 

As smart as I would like to think that I am, when I bought my first C5 back in 1998, I was discusted with the 1st to 2nd shift under power. The damn car would bog instantly.

At that time, I didn't realize that the traction control was so agressive. Once I figured that I could shut off the traction control (which shuts the throttle instantly), the problem went away. :yesnod:

The Z06 has a much more active use of the traction control, even from 2nd to 3rd.

Turn off the TC the next time, and see what happens. It may be that simple.

I appreciate your Kudos and look forward to working with you again. For folks that don't know, Jerome is an expert paraglider.

Jim Hall