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Discussion Starter #1
removing EMI from vehicle with EFI swap

i have an 90 F250 that i swapped in 96 Explorer 5.0 EFI and 4R70W trans. truck runs great has been for few years. but it seems like i have high amount of interference in the wiring. i need some advice on helping resolve

for example i have a Quarterhorse tuner and when i plug it into my laptop i can only have the laptop on battery power. if i plug in either of 2 cigarette lighter power adapters i have to power my laptop, the Quarterhorse will not be detected by the laptop. this can be troublesome for datalogging for extended times as it goes through batteries pretty fast. before i added ferite beads to the USB cable, i was unable to detect the QH with the engine on at all.

also the VSS uses a speedometer gear style sensor in the back of the trans, it will be accurate up to about 55mph, but once it goes faster, it will bug out and show all sorts of speeds and make some weird trans shifting. i use my OBD-II reader to view the VSS speed fro mthe PCM and its all over sometimes showing 0mph to 30mph when ill be doing 60. however the trucks speedometer is cable operated fro mthe same sensor and is accurate so i know its not the gear stripped. ive replaced the sensor 3 times so its not the sensor itself.

the radio has no issue in the speakers, theres only some other little issues ive noticed over the years but nothing specific. when i did the swap i spent alot of time making sure it was done correctly but it was ALOT of work took me months. basicly i swapped in a 92-96 truck engine bay harness because it has a power distribution box and much better wiring layout in general for a better basis. the 87-91 trucks have crappy wiring. everything engine and trans EFI wiring is pretty much stock Explorer wiring. both those harnesses form a triagular splice to the original truck wiring going to the dash. i added a second firewall connector for stuff like the OD button, OBDII port, and other such things.

other than making better grounds for the PCM, whats some things i can do to fix the EMI im getting?
 

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I'm curious what people offer up as solutions, as I seem to have some RFI issues, too. On the couple of occasions I've taken the car to track events, my Chase Cam videos have had quite a bit of noise in the picture, something I've never seen in the 3 other cars in which I've used the same camera setup. The camera and video recorder are powered off the 12V outlet, so I'm assuming that's where the noise is coming from.

Sounds like your issues are quite a bit worse than mine.
 

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Discussion Starter #5
Not knowing the frequency of your RF problems, try this.
https://www.stangnet.com/mustang-forums/threads/rfi-capacitor.639213/

Replace VSS no big deal, cheap too (also works the cruise control if there).
i replaced the sensor 3 times, the current one is Motorcraft. never changed.

Get your alt tested for ripple, scope

Or check setting meter on AC

Former is better
you know ya jsut brought up an obvious issue i have and completely forgotten about because ive gotten so use to it over the years. defiantly a probable cause of the issue. the alternator output is all over the place. its a Carquest 'new' 130amp and the voltage is almost never steady for long. i replaced it under warranty like 4 times in a month before i did the swap because the voltage jumped around soo much but it never fixed it. was bad enough that i can actually see headlights dim and brighten as i drove so i went to LED. i originally thought it was the old trucks shabby wiring but now with the swap and new wiring and instrument cluster, it still does it. only thing not replaced is the dash wiring. its been on my list of things to do is upgrade to a quality 240amp alternator because i added a winch to the truck recently.

only thing is even with the key on engine off, it still doesnt let me connect to the QuarterHorse. not sure if it would still cause the issue when not spinning. i might try unplugging the alternator and seeing what the truck does then. battery should be fine for good few miles of driving
 
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