"Pending" P030X codes, occasional engine misfire

[Rookie48]

More updates....

Replaced MAF
Replaced rear O2 sensors (previously only replaced front O2 sensors)

This made a small change - I can run between 65-75 MPH without any misfire codes being thrown. The engine is still stumbling slightly in this range (3000-3300 RPM). Stumble happens when at no or slight throttle and I am either letting off the throttle or accelerating.

It is still throwing only misfire codes across all cylinders at lower RPM's and at excessive highway speeds, again under the same throttle conditions as before.

Next steps (this weekend) are to:

Replace Vanos solenoids
Replace Cam sensors
Replace Crankshaft sensor

Vanos is not making any noise, and doesn't seem to be causing other typical symptoms (rough idle).

[jfoj]

Slow down here a bit.

Do not think this is anything to do with the VANOS.

Crank or cam signal, maybe?? But I do not think so because you are not loosing the Tach signal.

I believe you are loosing fuel for some reason. I see you replaced the fuel pump and filter already.

The loss of fuel and the O2 sensors going fully Lean will cause the Fuel System Status to turn to 8 or got into an error mode. This also cause the Fuel Trims to default to 0 as well.

I would replace the fuel pump relay or swap the horn and fuel pump relay first and see what happens. You may even want to rig up a test light or LED to watch and see if the fuel pump drops out.

As for Logging with OBDFusion, here are some set up options.

First change the MAF reading from Pounds/Min to Grams/Sec, stupid EASY.

Settings, Units, Airflow, choose g/s.

Temp sometimes can be more useful in C vs F, but no so critical.

Settings, Log Setup then set the following:

Logging Enabled - checked

Logging Trigger - choose Trigger at a fixed sample time

Sample Time - choose 1000 msec

Log GPS Items - suggest you unselect it as to not advertise where you live

Select Items to Log - This varies a bit for each car. But here is a list I like to see:

Fuel - do not check any of these 3 items

[Rookie48]

JFOJ:

Thanks for the support here.... I swapped the horn relay with the fuel pump relay, as well as changed the two cam sensors and the crank sensor. (Horn worked fine under either relay switch)

The truck is still not running very smoothly, and has thrown the misfire codes P0300 through P0306, but has not entered limp mode yet. It also threw the following codes, but I'm not convinced the scanner tool didn't misinterpret some code as it doesn't store these codes in the diagnostic report:

C0303 - Starting letter C diagnostic code suggests that there are problems in controller area network wiring bus and modules. Maybe this is for injector #3?
P0203 - Injector Circuit #3 Open
P0101 - Mass or Volume Air Flow Circuit Range/Performance Problem

I changed the log file settings and am attempting to record the logs during a misfire/limp mode condition. Will post here when I capture the event again.

[Rookie48]

Yeah, I agree with you. But my understanding of how the logger works is that it triggers on a PID value change, thus certain readings may be a few seconds old when they are written to the file.

I certainly know that I turned off the engine (while coasting at highway speeds) to clear the limp mode.

You can tell when the misfires happened - when the fuel status values go to "8". After that happens (3 times in this file, all highlighted in yellow), I would have to power cycle the engine to clear the misfires.

Looking at the MAF readings in relation to throttle position and calculated load where the misfires did not occur, they seem to track accordingly and as expected, but I'm not certain as I'm only looking at numbers here while not fully understanding all the logic... ;-)

BTW - should the MAF voltage range be 0 to 5 volts? The range seems much wider than that in my log files.


Rookie48

[SlickGT1]

Can you put what model you have in your signature. Kind of annoying looking through an entire thread to figure this out.

In open loop, as in cold start, the MAF readings are being ignored. Have you tried unplugging maf and driving around without it. You will get check engine. Try it. Check intake boot for tares.

[Rookie48]

Sorry about that, edited signature...

[Rookie48]

Pulled all connectors to the DME and reset. No sign of oil, water, or coolant intrusion on the pins. Will be taking a long trip this afternoon and will log and see if resetting the pins has had any effect. After resetting the pins, the truck started and ran fine.

Thanks for the support guys! Happy Holidays!

[Rookie48]

More data in the dropbox file below... no limp mode (fuel status "8") encountered, but still throwing misfire codes on all cylinders, no other codes.

https://dl.dropboxusercontent.com/u/...5%20PM%29.xlsx

One thing I keep noticing, but don't know if it is normal or not is the wide voltage gap at times between the #1 O2 sensor on bank and #1 O2 sensor on bank 2. At times one bank is way lean and the other is way rich. The second O2 sensors seems to be very consistent...

Also - I assume the data "drops" ("0" values) or lack of change in value over several seconds is simply the logger trying to record data faster than the ECU can provide it.

Thanks in advance for any data analysis here!

[jfoj]

Rookie,

The most recent Log that you posted looks pretty good overall.

Do not be worried about the differences you are seeing in the Pre-Cat O2 sensors. This is likely due to the polling sequence and the slower response of the cheaper/slower interface.

Also the O2 sensors dropping to 0 Volts is typically during Decel with Fuel Cut Off, notice the Fuel System Status is at 4 during these time windows.

The only thing I am really seeing that may be something to watch for is the engine coolant temperature may be slightly lower than expected. Typically the M54 should run pretty consistently at 96C except under heavy load or higher RPM when the thermostat heater is commanded on.

But without knowing more details on how long the engine had been running, what the ambient temps were and if it was raining hard at the time it is a bit tricky to know if the thermostat is slightly soft. I also do not expect the engine temperature concern to factor into the overall problem you were having.

I still need to look over the 3 earlier Logs you posted a bit closer, still trying to catch up after the holidays.

[upallnight]

Have you ever done a compression test on all the cylinders? A miss to the DME is a cylinder that is not producing as much power as the other cylinders. Also when you replaced the MAF was it with a siemens or some cheap piece of crap?