440 '7427 Running Issue

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WT91
Posts: 229
Joined: Thu Jul 02, 2015 12:00 am

440 '7427 Running Issue

Post by WT91 »

So I have made a ton of progress and now have another question/concern. I have my setup "Running" on the truck. It seems to do well, but every so often the otherwise very nice idle just drops and the engine either stalls or struggles to recover. I have no idea what could be causing this. TPS voltage is .6v with throttle closed, IAC counts are around 50 with the engine warmed up, when it goed into closed loop my BLMs are never very far from ideal, typically +/- 4 or 5 from 128. I am not running the knock sensor or esc, nor am i running EGR. There are no error codes. Fuel pressure is good, ICM is brand new, coil is brand new, timing is set at 4* advanced as per the 7.4L BMHK .bin I am using. I have corrected the .bin for the 74 lb/hr injectors I am using. I had some issues with a clogged fuel filter and then running out of gas but I have confirmed now that both the tank has fuel, the fuel pickup is sucking said fuel, and the filter is clean and filling with said fuel. I do see in my datalogs that there are some very strange spark advance numbers. Like 5000 degrees advanced at 2000rpm 45 map. Or 11000 advanced at 6800 RPM, which I have never revved the engine up to. I suspected the distributor, so I replaced everything in it. New magnetic pickup, new rotor, new cap. What could cause this?
  • 1990 Grand Wagoneer
    440 swap, 727 MVB, NP208, D44 F/R 4.10 gears ZIP locker up front Detroit out back. So much other stuff. Check out the build.
  • 1994 Ford F350 Crew Cab Dually
    7.3 PS, ZF5, 6.0 Intercooler, KC Turbo
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babywag
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Joined: Fri Jun 08, 2012 7:29 pm
Location: Land of Fruit Loops & Coconuts

Re: 440 '7427 Running Issue

Post by babywag »

WT91 wrote:I do see in my datalogs that there are some very strange spark advance numbers. Like 5000 degrees advanced at 2000rpm 45 map. Or 11000 advanced at 6800 RPM, which I have never revved the engine up to. I suspected the distributor, so I replaced everything in it. New magnetic pickup, new rotor, new cap. What could cause this?
I saw something similar on my '88 several years ago. Random rpm spikes in crazy rpm numbers.
Intermittent, like 1 sample out of hundreds, but they were there. Truck never acted strange or stalled though.
I replaced the wiring from ignition module to pickup coil w/ twisted pair wire, and never saw it again.
I'd guess it was picking up interference from something?
You can make your own twisted pair it isn't hard, but I already had a bunch laying around.
-Tony
'88 GW (aka Babywag)
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Tatsadasayago
Posts: 3684
Joined: Thu Aug 28, 2014 2:22 pm
Location: Sacramento, CA

Re: 440 '7427 Running Issue

Post by Tatsadasayago »

I would agree that your ECM is picking up RFI or EMI from somewhere...possibly the alternator diodes/rectifier.
If you can get ahold of a portable AM radio, tune it to the bottom of the scale, around 530 and walk around the idling vehicle with the antenna at right angles to the rig (Antenna vertical). If you hear ignition or charging system noise, tune across the band to find the strongest signal. Ignition noise (Snapping/rotary sound) makes the most noise at or around 530 and alternator (Higher pitched whirring)will peak out at or near the top of the scale.
Also, you can hold the radio in your hand and drive around listening for the intermittent ignition blip that will correspond to a snap, crackle or pop...which would be a body, frame or engine ground not making good contact.

Twisted pair wires act like an RF choke/filter and works great.
I make my own by chucking the wires into a portable drill, stretch them tight and slowly wind until there is a full wrap every 1/2" or so. Not only does this filter RFI/EMI but looks cool and is exceptionally manageable.
1977 Cherokee Chief - The Blair Jeep Project III
A collection of parts flying in close formation
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