That would make me think chain even more. It's very quiet whatever it is, and not cyclic like I'd imagine something related to the valve train or bottom end would be.
Best wishes with it!
I was pondering this a bit yesterday, and I do believe you've checked, but spraying some starting fluid around the intake manifold gaskets might identify an issue. I've also used the Gumout brand spray brake cleaner - it's mostly acetone. Up to you, but I'd steer far away from brakleen or...
Yep. All based on existing GMECM tech from the 80s. Automotive ECUs have the advantage of a BLM table... having a closed loop working in their favor. So you take the base fuel table which is burned in a UVEPROM, monitor the INT(egrator) under normal driving conditions, and that creates a...
Rigol has some decent ones for a pittance (relatively speaking). I recently picked up their entry-level DHO 4 channel scope, and I still have the older (but in some ways better) DS1054Z. There's no reason a decent o'scope should be thousands of dollars nowadays.
An open loop ECM has to take wild-ask-guesses to properly fuel the engine. When I used to tune ECMs back in ye olde GMECM days, most of my attention was done towards closed loop tuning. Often the open loop parts were almost afterthoughts. Pretty much every sensor is utilized in varying ways...
Good deal on the stethoscope. Worn chain would be my vote. I've never heard a camshaft make that noise. I have heard worn chains (contrary to popular belief, they cannot "stretch") sound similar. Does it change with differing RPM?
Plug color would indicate you're probably mixing fuel and air at the proper rates. 2° idle and 17° seems like not much. 4.3 is much like a small block V8 without a couple of cylinders, and they usually want much more. Might want to early it up until you start to hear some pinging, then back...
Doesn't sound like a ticking valve to me.
Maybe something with the water pump, since you've got the camera right next to it? It almost sounds like a loose/worn timing chain flopping around.
Engine stethoscopes are worth their weight in gold when you have issues like this.
That might not be outside the realm of possibility.
The big thing will be what it reads with the engine cold I guess. That will tell whether or not there's an issue there.
I'm not very familiar with the big block MPI system - does the computer control the timing directly with a crankshaft...
Oddly enough, I'm looking at my 1962 Pickett N-500-ES HI LOG|LOG which sits on the corner of my desk inviting comments from visitors. It's had a few, and I figure if the computer crashes, I can still compute VSWR.
Grr. That is frustrating, my friend! Nothing much fun about fixing a poorly running open-loop EFI system.
Have you swapped the coolant temperature sensor? I know things can go sideways real quick if the ECM doesn't know the correct engine temperature. And that temp isn't shown in your graphs.
1) Never go any faster than whatever speed you're comfortable hitting something.
2) To go slower than idle, just pop it in then right back out of gear. Make sure the drive is pointed in the direction you want to go before you do this. A stiff crosswind or rough water can make this REAL fun...
Indeed.
First camera was a home brew pinhole box camera using 126 film. 126 film in and of itself was not all that bad.
Then came the cheapo 110 cameras that really stepped backwards in quality, along with Kodak's Disc system.
Polariods always had their place with me - mostly in taking photos...
What codes are set in the ECM?
Replacing the temp gage sensor is just for the temp gage - not the ECM, so that would never have been a problem for the engine performance.
I don't understand what a "throttle body sensor" is - do you mean throttle position sensor? If so, and I had to take a WAG...
I've often seen people write that trimming a drive up while idling/running the engine on a sterndrive will kill u-joints in a hurry, and personally I don't do this, but I'd love for someone to explain the difference between trimming a drive up while steering is centered and having the drive down...
