Digplex ground helps but i'm still stumped

Having a stuble with my '80i 308 in the midrage area (4-5k rpm) .

I put an extra ground wire on each box and i gotta say the car has more punch to it than it ever had since i've owned it. I Can hear hear the once faint whistling louder now by far (birdcage thing is worse).I don't know if the grounding caused the digiplex to retard the timing or what but the car is more responsive. Previous grounds which i kept were mounted to metal held in place by fiberglass.

I'm stoked about this extra power.



Problem is that the stumble or sputter is still there. Not there when engine is cool but only happens when well warmed up (20+ minutes of driving). It's a whirling sound.. not just a sputter but a wha wha whaa sound (hard to explain the sound) It's has a feeling of reverbrations or a bouncing back and forth of the sound. Tach stays and doesn't fluctuate.


Spark plugs are a few years old but look good (NGK iridiums) All extenders look unburnt and nice (magnegor)

Those of you who haven't double grounded your boxes i highly suggest you do so.

Still stumped though.


Any ideas??? Thanks

 

Mine, too, ran better with some 10-gauge wire grounded to freshly cleaned metal. I gave the ground connections a quick shot of battery terminal protector so they stay that way, too! Mine also now idles better--especially when the fans are running--and I no longer have a faint glowing battery light at night when I put my turn signal on while headlights are up. All this from better grounds. . .

. . . and climb, I also cleaned the terminals of the connector with electrical cleaner, as the car's idle changed just from my moving the connectors around. And no, none of the pins are loose or bent! They didn't look dirty at all, but they were!

 

I just took it for another drive just to see if i was crazy. The car has a deeper note to it as well just hard to tell with the whistle from the injection plugs. Now i understand the complaints about the whistle.

What blew me away is that someone had used zip ties to reinforce the plug on both boxes and wedged little pieces of zip tie ends as shims to hold it tight. kinda rigged but done well (don't know how they got the ties so tight like that.)

Anyone have any more ideas on the studder??

 

They probably had a zip-tie gun. Little gun thingy that ratchets them real tight.

 

you are grounding to the chassis . . right? . . . use the 6 mm bolts toward the rear . . .as you've noticed . . .the fronts are mounted to fibreglass.

I noticed plug wire connections being "iffy" in the dizzies at times . . . my experience playing with my EFI is weak spark shows itself at peak torque when it really needs the spark . . . wiggle the wires while it's idling and see if you hear a difference (edit: don't forget the coil wire)

I'll microphone my engine one of these days . . I don't think the bird chirp you guys are hearing is anything like what I have with the brass plugs installed . .. in no way is it obvious or annoying . .. it actually just sounds like typical header reverb as I remember it.

cheers

 

Nice. Do you have pix of the new ground points?

 

No. It was a pain getting everything back in so i don't wanna undo it.

Basically on my car ('80i) there are four metal clamps holding the base for the digiplex boxes. Two of the metal clamps are held in with fiberglass (two clamps closer to the front). The factory grounds are mounted to the clamps held in place with fiberglass. I kept those grounds and just added two more and grounded to them to the back clamps as those are welded to metal.

It was easy. Just got some ring connectors and slid them right over the already existing nut (one on box and other on mounting clamp) and clamped the bolt down to hold it in place. I used 12 guage wire to connect. Looks a little half assed but the carpet does wonders for hiding it (wink goes here).

Home depot stuff.

BTW: found my sputter cause. Had a crack right down the center of an extender. Black electrical tape has held it off so far and the car runs with new vigor.

gonna need to replace that extender and another where i found some rust in the plug hole.

 

wasn't that way on my car . . .don't think that's factory . . that's not a ground by definition dude . . my grounds were connected to the rear mount points which are connected to the metal frame.


whether or not it's factory, if your car is this way it is wrong from a wiring perspective.

cheers

 

Someone must have switched 'em at some point. Even with fresh looking corrosion free grounds this was a weak point. Wish i'd done this sooner.

 

<aside>It's my understanding that the exhaust whistle is from the holey silencer insert
in the tail pipe extension which eventually rusts and becomes loose.</aside><onpoint>

Since my car is an 80i I wonder about unknowingly having this strange ignition problem.
Can someone confirm that the diagram below represents the afflicted ground from pin 9
of the ignition modules to G4 and/or post a picture of the afflicted ground?
Image Unavailable, Please Login

 

I don't know what pin the ground comes from but if you just pull the carpet back you'll see the grounds coming from the boxes. Their just mounted to the nut and bolt used to secure the digiplex mounting plate. There are four points where the mounting plate bolts to brackets built into the car. The two front (closer to front) brackets are secured in fiberglass and the back two are secured to metal. I'll i did was add two grounds and slid them into the existing nut and bolt of the brackets to the rear.