If you are encountering login problems please check here

Can a TFI drop out only one cylinder?
#1

Seems like an odd question, but I've run into an issue on the TBird where it's dropped out spark on the #4 cylinder.

The car has had a MS1 w/extra unit running a TFI distributor for a while now. This past week, I noticed that it was running like it was down a cylinder. Pulling plug wires confirmed that #4 was in question. After doing the parts shuffle, it didn't appear to be an injector issue, and when I was about ready to grab the compression tester, I double-checked for spark on that cylinder and got nothing. Every other cylinder would tick and jump spark to ground when it was pulled, but #4 was silent. Pulling the wire at the cap verified no spark.

Deeper investigation of the dist cap/rotor showed a loose coil terminal on the cap, which would loose continuity when it was wiggled. My summation was when the rotor would spin, it would rock things enough to drop out spark on that quadrant of the rotation. Odd, but I tested with the multimeter and seemed satisfied with that assumption.

New cap and rotor installed today, with fresh plugs. Same story. No spark on #4.

Is it possible for a TFI to drop a cylinder? I've only known them to just fail completely, and I didn't think they were "smart" enough to know any more than when told to spark by the Hall Effect sensor.
"Nobody can be so amusingly arrogant as a young man who has just discovered an old idea and thinks it is his own."
Reply
#2

.
I wuz wrong once before, Chuck ~ BUT......I doubt that your prob is being caused by the TFI module. 

If it's emanating from the primary/triggering "side" of the ignition circuit, my WAG would be something related to the PIP signal......like a broken/bent "shutter vane" or excessive dist-shaft wobble (from a worn housing or shaft) that's affecting the way the shutter moves past/thru the Hall-Effect pickup (PIP). My 2¢......  . [Image: confused0024.gif]
Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI
Reply
#3

Chuck, I chased a similar ignition issue for MONTHS.
It turned out to be the dissy drive gear. Both the auxiliary gear and the dizzy drive gear were worn to a sharp edge ONLY when the rotor was aimed at the #2 cylinder. This caused ONLY that cylinder to randomly fire, but mostly not fire. Replacing the Aux shaft and the dizzy gear cured all my ignition problems. Certainly worth pulling the dizzy completely out to make sure.
1986 SVO daily driver. PiMP v1.4/3" Stinger exhaust/FMIC/Schlodes Manifolds/Boport 2.1 and head/GM 3700 stall 200-4R auto trans
1963 2.3T Ranchero Project
Reply
#4

Yeah, I didn't *really* think the TFI would be the issue, but stranger things have happened.

I lost a dist/aux gear set YEARS ago, but haven't run into it since.

There is some rotational slop in the assembly, but I'm not sure what's spec. It could be off enough to cause the an issue. The car seems to rev clean, and it doesn't appear to miss when off-idle. I've always hated the dist/aux gear Achilles heel of these engines.

It's still just running the standard TFI settings in the MS tune, and has been fine for years, so it's possible that parts are worn. This car doesn't see many miles though...

I have noticed an occasional tick up in the idle, so it *may* be sparking once in a while.

When I get some time, I'll yank the dist and see what the gears look like.
"Nobody can be so amusingly arrogant as a young man who has just discovered an old idea and thinks it is his own."
Reply
#5

Well, now we know the rest of the story...

[Image: distgearworn.jpg]

Excessive wear in the one section on the dist gear. Hard to get a good view of the aux gear, but I'm sure it's about the same.

I have like 3 fresh-ish dist gears here, but I'll need to hunt down an aux shaft.
"Nobody can be so amusingly arrogant as a young man who has just discovered an old idea and thinks it is his own."
Reply
#6

That will do it! Glad you found the problem! I was about to junk my car over it!

The tooth count is almost exactly the 5-6 teeth to make it 25%( one cylinder). The gear slapping in and out of time really confuses Tuner Studio!.
For the future, I found it by connecting my timing light to each sparkplug wire and watching the flash( DON'T look directly at it, it is INTENSE!). All the other cylinders flashed perfectly, but the bad cylinder was all over the place!

I went ahead and bought an auxiliary shaft with the replaceable gear and the bronze dizzy gear. I think there is someone on TurboFord who had some stock auxiliary shaft for sale.
1986 SVO daily driver. PiMP v1.4/3" Stinger exhaust/FMIC/Schlodes Manifolds/Boport 2.1 and head/GM 3700 stall 200-4R auto trans
1963 2.3T Ranchero Project
Reply
#7

(07-18-2020, 10:31 PM)Howard Wrote:  DON'T look directly at [the timing-light flash], .it is INTENSE! 
.
OR......drop some acid beforehand and trip out, lol!!  .  [Image: happy0035.gif]
Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI
Reply
#8

(07-19-2020, 12:03 AM)TurboRay Wrote:  
(07-18-2020, 10:31 PM)Howard Wrote:  DON'T look directly at [the timing-light flash], .it is INTENSE! 
.
OR......drop some acid beforehand and trip out, lol!!  .  [Image: happy0035.gif]

And you KNOW why I gave that warning, right Ray????
DERP! Cry
1986 SVO daily driver. PiMP v1.4/3" Stinger exhaust/FMIC/Schlodes Manifolds/Boport 2.1 and head/GM 3700 stall 200-4R auto trans
1963 2.3T Ranchero Project
Reply
#9

(07-18-2020, 10:31 PM)Howard Wrote:  I went ahead and bought an auxiliary shaft with the replaceable gear and the bronze dizzy gear. I think there is someone on TurboFord who had some stock auxiliary shaft for sale.

Yeah. I don't think I need to get that spendy for this lump.

Just want to get it back together so I can enjoy it.
"Nobody can be so amusingly arrogant as a young man who has just discovered an old idea and thinks it is his own."
Reply
#10

(07-19-2020, 02:45 AM)Chuck W Wrote:  
(07-18-2020, 10:31 PM)Howard Wrote:  I went ahead and bought an auxiliary shaft with the replaceable gear and the bronze dizzy gear. I think there is someone on TurboFord who had some stock auxiliary shaft for sale.

Yeah. I don't think I need to get that spendy for this lump.

Just want to get it back together so I can enjoy it.

I hear you! I was told by people with a whole lot more knowledge than I advise against mixing and matching used stock auxiliary and dizzy gears, due to the difference in hardness after they are put in use. I did find a NOS auxy shaft but it was within $50 of the aftermarket!
Good luck!
1986 SVO daily driver. PiMP v1.4/3" Stinger exhaust/FMIC/Schlodes Manifolds/Boport 2.1 and head/GM 3700 stall 200-4R auto trans
1963 2.3T Ranchero Project
Reply




Users browsing this thread: 1 Guest(s)