This was done before I did any programming to my LT1 pcm, I've noticed upon acceleration either at a stand still in park, or driving off from a stop sign. My Spark Advance goes wayyyy high (up to 255 degrees), and I can actually feel the engine stumble abit when it dose it, I recorded it via Datamaster and I was wondering if anyone could give me any tips.

Now I will let everyone know that I did install a new Opti-Spark not to long ago.


Higher Res download

Screen capture

 

Are you driving a B-body? That's what you have it set to. Appears it's synched wrong. Impossible for the PCM to command 255-deg of spark advance, unless you entered that number in the tables, which would make no sense at all. And I can assure you, that with 255-deg of spark advance, your engine would not be running.

If you look in the lower right corner data panel, which shows the data for the frame you have the cursor on, it indicates 24.0-deg. Note that you have the same problem with your A/C pressure, which I've never seen in the lower right data panel, which does not match the A/C pressure shown on the main data panel.

You have something wrong in the DataMaster setup, or you are using the wrong version.

 

I'm currently using the current version of Datamaster, I am using a B-body (Roadmaster LT1)



High Res

 

Send a copy of the screen to TTS and ask them to explain it.

Nothing in the lower right "record" panel matches the corresponding data in the main display. Spark advance 24.0 vs 253.0; spark retard 0.0 vs 8.9.

Then look at the main display, and nothing makes sense. The engine is at 750RPM but the throttle is at 64.3%. MAP is 98kPa, indicating the equivalent of WOT. The A/C clutch request bit is "0" but the A/C pressure is 179.3psi.

Your second screen capture is a totally different frame, but the data in the main panel is IDENTICAL to the first screen shot. Virtually impossible.

 

Actually the reason why they are off is because the mouse is over the graphing data, this is data I have previously recorded, and not live data. The only thing i can think of is a possible misfire causing the spike

 

Still looks weird the top half of screen record 4274 shows TPS at 64.3% (3.0 volts) however your RPM16 is only at 799. MAP and AFGS look OK for goosing the throttle that high in park. Also your a/c temp shows n/a , not sure if that's a B-Body thing but DataMaster EE usually displays that reading correctly. What year Roadmaster is it ? Can you post a .uni file up on some FTP site. Or PM me and I'll give you an email address to send it to. Also there is a 46* stock "Max Timing Advance" setting in Tunercat constants table that limits advance to protect the engine. The 255 you are seeing (hex FF) looks like a PCM error or a display problem. As Fred said above firing with 255* advance the engine would not run. You would probably be firing somewhere in the exhaust cycle. However since you do have a noticeable miss at that time it could be the PCM or tune causing it.. ?? Do you have a stock tune or has it been modified. ??

 

I'll get ya the log file and a copy of my bin, Yes, I have since modified the PCM but only to disable the EGR, & AIR Pump. I have a 1994 Buick RM Wagon