What are the parameters that trigger engine code 17?
One of them is triggering engine code 17, which is giving me a spike in the Pulse width
(PW), doubling it for a very short time, and the engine misses once or twice.
Sometimes the PW issue doesn’t happen for 20 or 30 seconds and the engine idles just beautiful during that time. Then engine code 17 happens again causing a PW spike again. And on and on and on. It must be caused by a setting that I have wrong in my .msq.
The car is a 1971 Chevrolet, Monte Carlo, 350 CI, 4 bbl, automatic that I’m converting to TBI (454 7.4 Liter, 2 inch model), and it’s undrivable right now due to 2 problems that I know of; Pulse Width signals caused by engine code 17 and acceleration enrichment (accelerator pump) that I don’t know how to setup correctly. It spits and sputters even when I’m very, very easy on the throttle leaving a stop sign, maybe aggravated by the PW issue. It runs fine with the old carb with an AFR that normally is between 15:1 and 16:1. This was re-verified yesterday using MS_II with the TBI removed and the Quadrajet 4 bbl re-installed. It’s nice to be able to switch from carb to TBI in about an hour.
Here’s the engine test setup that I used this morning: This was a non-driving test, just an idle test in the driveway.
The spark bin is at 18 degrees everywhere (as shown on the MT screenshot and in the .msq).
The AFR is at 15:1 everywhere (as shown). Just in case EGO tried to change the VE, it didn’t. EGO was on so that I got AFR readings. It
And VE set everywhere to 30 as shown in the .msq file. It was running a little rich at 30 though.
My thought was to eliminate as many variables as I could so I could see the cause of the spike.
And I think I went through every recorded parameter in the MT list after I finished datalogging, to see what was causing the miss. I did. it was the extra fuel caused by the PW pulse.
OK, I have a fuel pulse width (PW) issue that causes the engine to stumble while idling. And it looks to be caused by an engine code 17. Which causes the PW to double for a split second, generally from about 1 – 10 seconds apart. Sometimes they come in multiples about a second apart sometimes further apart.
In MegaTune, engine code (17) just barely leads PW, which follows along with accel enrich.
This pulse causes a drop in RPM and a rise in MAP. And a slight spark advance. I didn’t expect the spark to change as the spark tables for this test setup was set to 18 degrees everywhere in the spark bin, If I stopped at a stop signal, in gear, sometimes the engine would quit.
Below is a screen shot showing the engine code 17 leading the other traces. Sometimes the leading shows up, at other times it doesn’t.
I still need to learn how to setup the acceleration so it doesn’t spit and sputter when leaving a stop sign. Would any one mind looking at the acceleration enrichment setting in my .msq, it’s probably the default, and give me some ideas as to what I’m not seeing or doing. Thanks. Remembering this is a TBI, not tuned port.
And, It would be nice to know how to fix the blue line and yellow squares (shown on the screenshot on the 20 kPa line in the MT AFR table) so that they aligned with the reported MAP from MT as shown in the screenshot of the MAP value (yellow line reported at 34.
. It always shows up on the bottom kPa line, 20 instead of somewhere around the 35.To all that help me on this, I Thank you, and my wife thanks you.
Holl