Resolved: 1996 5.7L Scorpion Backfire

[Reel Poor]

Re: Resolved: 1996 5.7L Scorpion Backfire

Dave will that software do live data feed or just a data file by e-mail, and is it a movie or a snap shot?

 

[newport dave]

Re: Resolved: 1996 5.7L Scorpion Backfire

Reel,<br />The Diacom software connects to the DLC and can view, record, and play back all the data available from the ECM. It also does all the standard trouble code info and diagnostic tests (what tests it can do depends on the ECM type).<br /><br />The recorded files contain multiple "frames", each frame containing all data parameters. The recorded files can be played back and viewed just like you were connected up to the engine. <br /><br />In my opinion Diacom is a "must have" for any tech. Combine Diacom with a PC based engine analyzer (as shown in the second screeen shot), and a library of service manuals on PDF, and a laptop becomes a very powerful diagnostic tool.<br /><br />Dave<br /><br />Diacom playback<br />

<br /><br />Diacom w/ engine analyzer<br />

 

[Reel Poor]

Re: Resolved: 1996 5.7L Scorpion Backfire

Thanks Dave, I'm a little familiar with the software, just didn't know if you gould E-Mail a movie or a snap shot of the data.

 

[jwaymer]

Re: Resolved: 1996 5.7L Scorpion Backfire

Originally posted by newport dave:<br /> Any chance of looking at the data you recorded? I have Diacom also and if you could email me a copy of the data file, I would like to take at look at it. <br />Dave

Yes I can email two recordings I made...one a full throttle accel, the other a gradual acceleration.<br /><br />P.S. the way you have your Diacom screen setup is awsome...I'll have to try that!

 

[newport dave]

Re: Resolved: 1996 5.7L Scorpion Backfire

My email is (email address deleted)<br /><br />Dave

 

[newport dave]

Re: Resolved: 1996 5.7L Scorpion Backfire

I looked at the data and found a couple things that I though were interesting. First, the backfires occurred after the Injector Pulse Width had flattened out, but the throttle position continued to advance (more air, no more fuel). You can even see some knock sensor activity after the first backfire.<br /><br />Second, The backfires occured immediatly after Power Enrichment Mode was activated.<br /><br />Third, the Throttle Follower Bias is not following the throttle like it should. At a few points on the recording it would go to 255 (all the way open) briefly, and then back down to zero. Don't really know why it would read incorrectly like that.<br /><br />I made a graph of a few of the engine parameters. Keep in mind that I have adjusted (multiplied or divided by a factor of 10) some of the parameters so they all share a similar scale. Note how the highlighted areas where the engine is seriously faltering (decreasing RPMS despite increasing throttle position) is where the relationship between Throttle Position and Injector pulse Width change.<br /><br />Dave<br /><br />

 

[DJ]

Re: Resolved: 1996 5.7L Scorpion Backfire

All the electronics in the world won't cure a basic engine problem. We tend to blame the "black boxes" first.<br /><br />Hook up a vacuum guage to a non ported intake manifold port. This would be downstream of the throttle plate(s). You should get a steady needle, at idle, in the 16 to 20 in./hg range. If the needle fluctuates, you most likely have a valve problem.<br /><br />You should also get a steady needle at cruise speeds.

 

[jwaymer]

Re: Resolved: 1996 5.7L Scorpion Backfire

Sorry I haven't updated in a while...been travelling too much. <br /><br />The problem has been fixed! My friend had another one of his friends (boat mechanic by trade) take a look at it. He used a multimeter to check the TPS. I'm not quite sure what he found (said something about "one side" was reading fine, but the other wasn't), but he was certain it was the problem...they replaced it and everything is OK now.<br /><br />Thanks to everyone for your help. And thanks Newport Dave for the data analysis. If you have the data still can you see anything that indicates the TPS as the problem (hindsight being 20/20)? Also, point #2 on your post with the chart...I had him advance the throttle fully without the engine running to see if it was reading correctly...I think that's what you are referring to. Also, what did you use to make the chart?<br /><br />Thanks again, <br />Jason

 

[newport dave]

Re: Resolved: 1996 5.7L Scorpion Backfire

Jason,<br />I did not see any indication of a problem with the TPS. I did see in the data file that before you started the engine you moved the throttle to WOT and back three times. I suspected that might have been you checking the TPS, and the results looked normal to me. <br /><br />What I was trying to say earlier was that the problem seemed to be how the ECM (Injector Pulse Width) was reacting to the TPS input, not in the TPS itself. Glad that you found the problem and sorry that I was not able to be of much help.<br /><br />The chart is generated in Microsoft Excel from imported data from Diacom. Then I used a screen capture program (called SnagIt) to capture the chart as a JPG file and add labels and stuff.<br /><br />Any chance of getting a new (after repair) data file? Maybe I could figure out if I missed something.<br /><br />Dave