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Carport? Conduct visual inspection and look for chewed wires, particularly on the O2 sensor harnesses.
We've already done that; no issues nor evidence of chewed wires anywhere. My friend is obsessed with going through the entire wiring harness in the car looking for chewed wires; I'm afraid he's going to cause more problems and solve none.
We've already done that; no issues nor evidence of chewed wires anywhere. My friend is obsessed with going through the entire wiring harness in the car looking for chewed wires; I'm afraid he's going to cause more problems and solve none.
Does your buddy have HPTuners? There are some very specific things that can be done with their scan tool to command the ECU to do things, let alone read how the engine is running.
Seems awfully foolish to chase wiring blindly. Ain't my car though. Best of luck. Sounds like the kind of person that maybe shouldn't be doing any in depth work on cars.
We've already done that; no issues nor evidence of chewed wires anywhere. My friend is obsessed with going through the entire wiring harness in the car looking for chewed wires; I'm afraid he's going to cause more problems and solve none.
Did you look at those Data PIDS I had suggested…your always start with live data to diagnose something like this !!
Does your buddy have HPTuners? There are some very specific things that can be done with their scan tool to command the ECU to do things, let alone read how the engine is running.
Seems awfully foolish to chase wiring blindly. Ain't my car though. Best of luck. Sounds like the kind of person that maybe shouldn't be doing any in depth work on cars.
No, neither he nor I do.
Originally Posted by C5 Diag
Did you look at those Data PIDS I had suggested…your always start with live data to diagnose something like this !!
Did you look at those Data PIDS I had suggested…your always start with live data to diagnose something like this !!
Friend had his car brought to my house. So, question: would you want to see the O2 voltages by themselves, and the MAP/MAF relationship separate? (assuming the fewer parameters recorded will give me higher recording rate).
Friend had his car brought to my house. So, question: would you want to see the O2 voltages by themselves, and the MAP/MAF relationship separate? (assuming the fewer parameters recorded will give me higher recording rate).
Thanks for the help, and have a good one,
Mike
Mike, first thing I do is (KOEO) key on engine off I always will look at the MAP PID and see what it reads…I also look at ECT also may
making sure both are not skewed…MAF you want to look at “hot unloaded” idle…O2’s you look at in a graph form if your scan tool has the capability…yes, less data PIDS make the refresh rate faster…these are the PIDS I normally look at for any drivability issue.
Okay, finally got my act together and got some data.
1. Car is driving fine, no engine codes
2. KOEO, Cold: MAP: 29.2 in Hg, IAT; 86, Ambient: 81, ECT: 77
3. After test drive (20 minutes?), KOER: MAP: 9.2, MAF: 0.9, IAT: 100
For the 1st 5 minutes running, essentially at idle, the O2 voltage readings didn't change. It took 5 minutes for me to figure out that I was recording data correctly. I gathered 2 sets of data: the first is just the O2 sensors, that I've decomposed and found something that, while it's not throwing a code, nor even noticeable, might be indicative.
Look at the two charts, from time period 550 to 600 (seconds). Bank 1 Sensor 1 (B1S1) has similar activity to the time periods on either side, while B2S1 shows virtually no activity. But otherwise during this part of the graph the two are fairly well aligned.
Any ideas?
Thanks again for the help, and have a good one,
Mike
Those O2 sensor waveforms look rather odd...200-800mV's is what you should see...your O2's are going well over 1 volt also...below is a good waveform...the other data PIDS look OK
Here's another set of data that I gathered on that same run, this has calculated load (scaled to 200% to get it down below the O2 graphs) added:
What is your load at idle ??…it’s usually less than 5% or so…other than graphing the O2’s it just easier looking at a number…are the fuel trims still negative??…clogged cats can sometimes drive the fuel trims negative.
Sorry for the delay: last night we had a huge hailstorm come through our neighborhood (2.5-3" hailstones plus wind), which knocked out the power for over 22 hours.
I looked at the calculated load value, and at a stop (in gear IIRC), it's stable at 20%. It never goes below 10%. I'll check fuel trims when I get the mess cleaned up and get back on the car.
Got some more data today. Started up recording short and long term fuel trims with calculated engine load. As you'd expect, short term trims rapidly changed, following the O2 sensors. The long term trims were all negative: here's a graph of a rather typical 2 minute stretch. Note there's one point where the trims limit out at -25%:
The other interesting thing were fault codes. I checked them right after startup, and I had thirty codes! This after the previous run had zero. I left them alone (check engine light was on) and did my test drive. Car drove fine, with the exception of a few sluggish shifts while the transmission was cold (I don't have much experience with the C7's A8 tranny, so I don't know if this is normal or not). After around a 20 minute run, I checked the codes again, and all but 5 had self-cleared. The five that remained were the O2 sensors and heaters, plus one for the fuel pump controller (which we've already replaced).
I then cleared the codes, with the fuel pump controller code remaining. I also scanned all the systems that I could, and documented and cleared several BCM codes and one human interface (?) code. The files are attached in pdf format.
Thanks again for your help, and have a good one,
Mike
One thing I forgot to mention: for some reason the drive modes were inhibited during that last test drive. Any idea as to what would cause that to happen?
Got some more data today. Started up recording short and long term fuel trims with calculated engine load. As you'd expect, short term trims rapidly changed, following the O2 sensors. The long term trims were all negative: here's a graph of a rather typical 2 minute stretch. Note there's one point where the trims limit out at -25%:
The other interesting thing were fault codes. I checked them right after startup, and I had thirty codes! This after the previous run had zero. I left them alone (check engine light was on) and did my test drive. Car drove fine, with the exception of a few sluggish shifts while the transmission was cold (I don't have much experience with the C7's A8 tranny, so I don't know if this is normal or not). After around a 20 minute run, I checked the codes again, and all but 5 had self-cleared. The five that remained were the O2 sensors and heaters, plus one for the fuel pump controller (which we've already replaced).
I then cleared the codes, with the fuel pump controller code remaining. I also scanned all the systems that I could, and documented and cleared several BCM codes and one human interface (?) code. The files are attached in pdf format.
Thanks again for your help, and have a good one,
Mike
That is a lot of codes that sort of seem unrelated in the sense of it's not common that one would affect the other. I would start by investigating electrical connections, specifically the following areas.
#1) All battery connections including the positive terminal fuse block and black wire in the trunk.
#2) In the engine compartment, the positive terminals that attach the the fuse box. Verify any connection issue here or a loose nut for the positive wires.
#3) The fuse box under the hood itself. It it was ever removed and not re-installed properly, there could be loose connections underneath causing intermittent issues.
#4) Pop the passenger side front tire off and pull back the wheel liner side closest to the passenger door. Take a look at the ECU and its connections. Do any of them look loose or like they may have had water intrusion? They are pretty resilient but if water got in there, it could be a problem.
