Nothing unusual about 40* spark advance at a 2097 rpm, 64 mph cruise. Spark tables are very complex and can range from negative spark advance all the way up to 45* advanced given throttle command, load, deceleration or acceleration, etc. Everything looks very normal in the screenshot you've posted.

Remember that several of the PIDS pulled off the OBD connector are "calculated and not representative of real values. PIDS such as AFR, fuel pressure.

Only thing I see that causes any question on my part is bottom right corner. Warmups since DTC cleared 7 counts and warmups without Emission faults. What DTC?

 

Thanks for the reply Blindspot.
I needed that because i had seen figures of total spark of 27deg and seeing 40deg made me look towards ignition for my hesitation/misfire condition, so will look towards maybe a fuel delivery issue as my next tests.

Cleared DTC's were to do with seat restraint system and a couple of HVAC issues, no engine DTC's at all since iv owned the car for the last 12 months
Cheers

 

Here is a capture of the high octanne spark table on a stock E38 ECM. You have an E40, but this will very close to this if not identical. This is not the whole table as spark air mass goes all the way up to 1.36 but I couldn't capture the entire table.

This will give you a snapshot of the variety of spark advance at any moment in time. As I've told you before, it is very difficult to analyze engine management status on snapshot screens. I have a Tech II as well, and if you really have misfires, in the rpm range, the tech II will record it.

 

That's great thanks, how do i read the left vertical column of spark airmass, what does that relate to say on my Tech2, or do i need Hptuners to log the info (i will be getting Hptuners unit in September, once i have the funds)
I will run a few misfire data logs tomorrow and see what RPM's they are occurring.

 

Spark air mass or cylinder air mass gets very complicated, too much for here. If you're curious google it and start reading.

BTW - simply looking at a spark table doesn't tell you the whole story by a significant amount. There are SEVERAL spark modifier tables that influence the final spark the engine sees. This spark table is the basis from which the modifiers are applied for numerous reasons. Just to name two modifiers - IAT and KR.

 

Google here i come.

 

HPT has a great forum. Sign up there and search and or spend some time on the GM Gen 4 forum. There are some very sharp people over there and I've learned more about tuning right there than any other source.

 

Already a member of HPT, going to check out the GM Gen 4 as well. Thanks again.

 

BTW, I know you've been chasing these random misfires under acceleration for a while now. Something that is a little off the path you might want to check is fuel pressure. Here is where the Tech II is not going to help you BC that PID is not actual fuel pressure but calculated.

You might want to get a gauge on the end of the fuel rail and get a real FP reading under different RPM and acceleration situations. Verify that FP is not falling off when needed the most. A weak pump or a dirty screen off the pump in the tank can cause that.

 

Yeah iv been struggling for a little while now chasing down the issue, i know you've helped me a few times now
Your on the money about the fuel pressure being an avenue to check out.
Ive got a full fuel tester (with schrader) arriving on Thursday so will be checkin FP through rev range as my next diagnostic now you've helped me clear up the ignition query.

 

For airmass a rough estimate would be

MAF (g/sec) x 15 / RPM

Not exact but decent ballpark

Much easier to see in HPTuners but ignition advance isn't the cause of your misfire IMO.

 

Let me give a start, but this is pretty basic. Doing this BC I think what you might really want to know is - What action has a causal effect on the vertical axis of the spark table.

Focus on Relative Throttle position as a percentage. Relative Throttle, Commanded Throttle and Actual Throttle are all different, but for a hypothetical, let's just say that commanded and relative throttle are the same thing:

With that, here are two hypotheticals - Let's put you in a C6 with a manual trans:

Scenario #1 - Start from a dead stop in first gear, accelerate all the way to redline while holding a commanded throttle of 30% the entire time.

Scenario #2 - Start from a dead stop and accelerate all the way to redline, only this time, commanded 100% throttle the entire time.

In these two scenarios, the ECM is going to take different paths along the X and the Y axis to get from idle RPM to redline RPM.


Now you can begin to think about cylinder air mass as the volume of air allowed to enter past the TB's butterfly valve and into the cylinders, as a charge, at different RPMs and different TPs. The vertical column will start to make some sense. BTW, deceleration, along with fuel cutoff (DFCO) also takes it's own path on the table going back to idle.

To your question, the Tech II won't provide much and will do nothing to analyze the spark table, but I agree with Schpenxel ign adv has nothing to do with your issue, just satisfying your curiosity about the 40* adv that you saw. In HPT however, you can use a spark adv graph in a datalog and track the path the ECM took.