Hi guys,
since 2 days my C7 (M7 Z51) developed a weird issue.

Basically the car starts perfectly, idles perfectly and drive perfectly on the whole RPM as long as you are not in WOT.

If I accelerate fully at any RPM, it starts to cut power making a sound to the exhaust very similar to a Traction Control intervening or an Ignition/Spark cut.
the best image could describe it is like those "Fart" made by modern dual clutch performance cars while shifting, but it's continuous until i left the throttle.
ofcourse the performance are reduced, I'd say by a 50%.

Now, i have no CEL, no misfire codes, nothing.
I checked also on live data with HP Tuners and except few misfires (contained), nothing really evident.

Also, I replaced Spark Plugs and wires around 2 months ago, since that i did probably 1k miles.

I think the first thing would be to pull all the plugs and wires and see if some got bad for some reasons.

weird thing is that, if i don't wot, the car runs perfectly, idle, moderate throttle, no misfires at all.

(NOTE: does the same with TC off, so it's not the traction control intervening)

Any clue?

 

What data PIDS are you graphing with HP Tuners ??…that thing is only a “generic” scan tool so you won’t have as many PIDS to look at vs a factory level one…at WOT your front O2 sensor should go full rich (over 900mv’s) and if a cat getting clogged you would see an increase in MAP and IAT..exhaust gases aren’t going out the tail pipe but backing up into the intake manifold…how about fuel rail pressure ??…with VVL I don’t know if your scan tool can look at camshaft “desired” vs “actual” position..when the camshaft “phases” I think you should be seeing the camshaft fully retarded at 26.5 degrees…if off that much I think you would see a P0016.

 

Hi
Thanks for tge hint.
no cat clogging, I'm running long tube catless headers.

 

1) list mods. If you've done stuff like swap the cam and gotten rid of VVT and DoD, some things won't apply
2) Remove the plug wire from each coil and then re-seat it. Had one with similar symptoms and the plug wire was still on the coil but not fully seated. This can also happen on the plug side. Happened on my engine....no CEL, fine at idle and cruise, horrible at WOT. Plug wire was barely on the plug.

3) If you have an HP Tuners log, post it and I'll take a look tomorrow to see if anything jumps out.

 

Thanks, car bone stock except tune and headers.
Lifters for DOD still in but never ever activated once (been turned off via Tune from day one) as it's a new engine crate i have in since 3 years around, 40k miles.

 

One things that I noticed is that it doesn't happen within the first 10 minutes of car startup.
it goes normally, also at WOT.
after around around 10/15 minutes of usage, it starts to cut at wot.
I'm thinking of some sensors at this point, reading some bad values, and preventing the car to go wot properly, and cutting instead.

 

All interesting but unless you've checked all the plug wires and logged data, that's all it is....interesting.

Coils sometimes show these symptoms....fine when cold and fail when hot. Ditto injectors.

Well before the 10-15 minute mark, the car is warmed up, it's in Closed Loop for probably 7-8 of those minutes (unless it's 0* outside), it's been using all the sensor inputs. None of that points to a sensor issue.

 

Tomorrow will change all the plugs, checking plug wires and do a LOG to post here, thanks for the interest.

 

I was doing some idle testing but this gives you an idea of how quickly it can go into closed loop....not quite 28 seconds after startup. Yes it's hot outside so that matters, but the point is that unless you're in late fall or winter type of weather, the PCM is running closed loop well before you're seeing issues.

 

Thanks for the info, it's definitely hot in here around 86° Farhenite, so that's definitely the case.
tomorrow will change all the spark plugs and post a LOG.
Thanks again

 

Hi,
small update today:

yet as told the car has not giving any CEL or DTCs, by switching to the "Current" to the "From last start cycle" page, i found stored 40 DTCs, that apparently were not visible but stored:

nspection Report
ECM (Engine Control Module)

DTC No. (40)

P0101-00 Camshaft Position System Performance
P0099-00 Intake Air Temperature (IAT) Sensor 2 Performance
P00C6-00 Fuel Flow Pressure Low During Engine Cranking
P0111-00 Intake Air Temperature (IAT) Sensor Performance
P0116-00 Engine Coolant Temperature (ECT) Sensor Performance
P0128-00 Engine Coolant Temperature (ECT) Below Thermostat Set Temperature
P0133-00 Heated O2 Sensor Slow Response, Line 1, Sensor 1
P0138-00 HO2S Sensor High Voltage, Bank 1, Sensor 2
P0159-00 Heated O2 Sensor Slow Response, Line 2, Sensor 2
P0160-00 Heated O2 Sensor High Voltage, Line 2, Sensor 2
P0154-00 Heated O2 Sensor Line 1 Delayed Rich-to-Lean Response
P0156-00 Heated O2 Sensor Line 1 Delayed Lean-to-Rich Response
P0161-00 HO2S Sensor 1, Bank 2 Delayed Rich-to-Lean Response
P0160-00 HO2S Sensor 1, Bank 2 Delayed Lean-to-Rich Response
P0420-00 Catalyst System Performance, Bank 1
P0430-00 Catalyst System Performance, Bank 2
P0101-00 Fuel Level Sensor Performance
P0720-00 Incorrect Gear Ratio
P0734-00 Incorrect Gear Ratio
P0735-00 Incorrect Gear Ratio
P0737-00 Incorrect 7th Gear Ratio
P1F13-00 Fuel Reduction Module Performance
P2066-00 Fuel Level Sensor Performance 2
P2270-00 Heated oxygen sensor signal stuck lean, sensor line 1 2 P2271-00 Heated O2 Sensor Signal Stuck Rich, Bank 1 Sensor 2
P2272-00 Heated O2 Sensor Signal Stuck Lean, Line 2 Sensor 2
P2273-00 Heated O2 Sensor Signal Stuck Rich, Line 2 Sensor 2
P1900-00 Cylinder Deactivation System DTC
P3401-00 Cylinder 1 Deactivation Solenoid Valve Control Circuit
P3403-00 Cylinder 1 Deactivation Solenoid Valve Control Circuit High Voltage
P3425-00 Cylinder 4 Deactivation Solenoid Valve Control Circuit Low Voltage
P3427-00 Cylinder 4 Deactivation Solenoid Valve Control Circuit Low Voltage
P3428-00 Cylinder 4 Deactivation Solenoid Valve Control Circuit High Voltage
P3441-00 Cylinder 6 Deactivation Solenoid Valve Control Circuit High Voltage
P3443-00 Cylinder 6 Deactivation Solenoid Valve Control Circuit Low Voltage Cylinder 6 Deactivation Solenoid Valve
P3444-00 Cylinder 6 Deactivation Solenoid Valve Control Circuit High Voltage
P3440-00 Cylinder 7 Deactivation Solenoid Valve Control Circuit Low Voltage
P3441-00 Cylinder 7 Deactivation Solenoid Valve Control Circuit Low Voltage
P3462-00 Cylinder 7 Deactivation Solenoid Valve Control Circuit High Voltage

This thing makes me think of an harness/connector issue at this point, maybe for the harness going from the ECM to the Engine, as it looks all engine sensor related issues.

 

It is impossible to have these many DTC’s stored from the last “start cycle”…are you reading these in “scanner or “editor”…the DTC’s should be read in the scanner…maybe you can post a pic...I don’t use this tool for other than adjusting some parameters like fan settings so I don’t know where you are reading this…if you had these many the car would not run…if you want to diagnose this yourself you need the proper scan tool and HP Tuners is not it.

 

I have other tools like Launch and GDS2 that both give the exact same errors. Both of them not showing it in any moment in current DTCs, i have no CEL and if I scan the car I have no DTCs.
but if I go on previous cycles or from last DTC erase it has that list that you see.

 

This is from my Launch…are you looking at “Additional DTC Information” ??…if you are don’t !!…those are not the current or pending DTC’s…under not ran since codes cleared are the tests the ECM has not run…those are not your DTC’s.

 

Will be sending Launch screen pictures once i get home.

 

If you are looking at Not Ran Since Codes Cleared…

 

Just because you turn off codes doesn't mean the tests aren't still run (and recorded) in the background. Those are artifacts from turning off o2 codes for the headers and DoD. The few others are likely artifacts from past issues or other changes made to the car over time.

P0420 and P0430 are the most talked about two online. Guys install headers and then start the car on a stock tune. They then take it to a shop for the real tune. P0420 and P0430 will remain in the system until someone hooks up the rear o2 sensors and the PCM can successfully complete the tests.

TLDR.....Just because the CEL isn't illuminated or a failure is not reported doesn't mean tests aren't still performed (and failed) in the background.

As before.....interesting information...not pertinent to the issue at hand.

 

My car is running headers and tune since 5 years, and never once those errors appeared, i did hundreds of diagnosis since.

 

You have my thoughts on the matter. Good luck.

 

I'm just stating facts, not here to fight anyone.
If you tell me "those errors have always been there" i tell you 2 weeks ago, and the 5 years before never appeared once.
tell me whats hurting you about?