Hello All,
89 Ford Mustang 5.0. Stock ECU with chip and tuning software, stock ignition. Typical mods of aftermarket heads, cam and intake.
Hantek 1008c
Unforutnately, with the combination of parts, I cannot run the car without the chip (mainly the injector and MAF combination), so I'm not 100% sure if the chip is the cause.
I've been dealing with a periodic idle misfire and an odd leaning out at a specific rpm range (1600-1900 RPM).
I have the below thread on the idle misfire, but wanted to create another one to discuss scoping.
www.scannerdanner.com/forum/post-your-re...-0-idle-misfire.html
Anyway, so I had the scope hooked up earlier this summer and was trying to scope different things.
Injector PW, TFI module signals, coil primary and secondary and current....etc.
Injector PW, TFI module signals and coil primary current all looked good. No dropped signals.
Coil primary and secondary were inconsistent.
Coi primary voltage showed inconsistent spark lines as well as secondary from coil to distributor, which would make sense for misfire. I think I have images in my post above.
When I had the HT lead on the coil to distributor wire, I would get consistent signal (but inconsistent spark line). Sometimes I would get a good spike and burn line, other times not.
When I connected that HT lead to after distributor (individual cylinders), the signal would get muddy. The spark line was good/bad/missing altogether……not consistent enough.
What’s even more interesting is that I had to place the HT lead right at the distributor to get anything. If I moved it closer to the spark plug, it would get worse and more inconsistent signal.
This is with 8mm standard plug wires. When I had my 9mm Ford Racing wires, I could not get any signal at all (before or after distributor). Both plug wire sets have the same misfire. I played with the settings in the software to change the scaling, but all that did was add/subtract electrical noise.
I did a leakdown test and everything was good enough. I had one cylinder a little lower than the others, but all leakdown was past the rings, nothing past the valves.
For the leaning out issue between 1600 and 1900 rpm, this is something that I can see in my real time datalogging. What’s odd is that pretty much right at 1900rpm, it’s like a switch and the engine starts to run rich and ECU compensates in closed loop. I can also feel it pick up in power. I’ve had this issue for the past 15 years and usually just deal with it, but I’d like to figure out why it’s happening. What really sucks is that rpm range is right where I drive probably 80%+ of the time. That is another part of the scoping and my confusion with the HT lead before/after distributor. I wonder if it’s a spark issue and not a fueling issue.
Sorry for the long book, but if you’ve made it this far, any thoughts?
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