Fox Mustang: I want to bypass TFI module.

[5.0Thunder]

Hey guys, my car developed a misfire at all rpm after some good hard pulls and I have a feeling it's ignition related, likely MSD coil or TFI module took a dump, not sure yet. I'll be doing some diagnostics to find the culprit but it all got me re-thinking about ditching the TFI stuff in this car.

The setup uses a factory 1990 mustang ignition with an MSD coil and MSD 6AL and MSD 8874 patch harness. I believe this allows the TFI module to trigger the 6AL to fire the coil. I have bypassed the 6AL with no change in misfire so i'll assume the 6AL is okay.

Could I take the crank position signal from the TFI module like normal, then trigger the 6AL with megasquirt rather than letting the TFI module trigger it? Will this essentially bypass the issues normally associated with TFI modules?

Another idea was grabbing a 36-1 trigger wheel and sensor and wiring the sensor to MS then firing the coil directly, which is most preferable of all but then I deal with the pains/expense of pulley spacing or balancer milling. There doesn't seem to be a simple bolt on solution for this as far as I can tell.

[Blown88GT]

Hey guys, my car developed a misfire at all rpm after some good hard pulls and I have a feeling it's ignition related, likely MSD coil or TFI module took a dump, not sure yet. I'll be doing some diagnostics to find the culprit but it all got me re-thinking about ditching the TFI stuff in this car.

The setup uses a factory 1990 mustang ignition with an MSD coil and MSD 6AL and MSD 8874 patch harness. I believe this allows the TFI module to trigger the 6AL to fire the coil. I have bypassed the 6AL with no change in misfire so i'll assume the 6AL is okay.

1. Could I take the crank position signal from the TFI module like normal, then trigger the 6AL with megasquirt rather than letting the TFI module trigger it?
2. Will this essentially bypass the issues normally associated with TFI modules?

Another idea was grabbing a 36-1 trigger wheel and sensor and wiring the sensor to MS then firing the coil directly, which is most preferable of all but then I deal with the pains/expense of pulley spacing or balancer milling. There doesn't seem to be a simple bolt on solution for this as far as I can tell.

Misfire at all rpm's is a symptom I've not heard of for a bad TFI. They either work or don't work. The temp range of the chips inside had a maximum rating of 257degF. With a 192deg t-stat, you're getting very close. 180deg t-stat seems to solve the temp problem. Later vehicles, Ford relocated the TFI off the distributor to a heat sink mounted in the engine bay. I tried relocating it & could not get it to work, even with an extension harness fabricated same as Ford harness, i.e. double shielding to mil-spec. I got frustrated with it & gave up.
https://www.autosafety.org/ford-tfi-mod ... ettlement/
1. Yes. https://www.diyautotune.com/support/tec ... stang-5-0/
2. Don't know. Seems more trouble than it's worth.
I can't use a trigger wheel because there is no room for it all. The larger supercharger/accessory pulley is already too close to the electric fan.
If you have the room, EDIS is the way to go while you can still get all the parts from the junkyard. They crush cars after 20-25 years.

[5.0Thunder]

Good info, I'd hope the TFI isn't the culprit, we'll see after some testing.

First on my list, I checked the MSD cap and rotor (I bought a bunch of MSD stuff back when I thought they were good...). I pulled the cap and see the center post that the rotor touches is basically a little nub. The stock cap had a longer center post so I popped a stock cap back on it and fired the car and it was smoother at cranking and when it idled down it goes pig rich and starts fouling plugs. Lol Normally about 12.5AFR at cold start, it sits at 10AFR with stock cap. I swap the MSD cap back on and restart, AFR is 13.5ish. I pull the cap and bend the rotor "prong" up to contact the center nub better. Fire it up, 10-10.5AFR.

This makes me think the MSD center nub wasn't in contact with the rotor prong so it wasn't completely burning the mixture, leaving unburned fuel in the exhaust. When using stock cap or bending the prong, spark may be stronger so more fuel is burned, resulting in the richer AFR.

Does this make sense? I'm thinking I'll replace the cap with new and retune my fuel table for the better spark, assuming this was the misfure culprit. I do have a new stock coil coming in the mail so I may throw that in to get the MSD coil out of there.

[5.0Thunder]

Now I'm thinking unburned fuel should show rich and the new cap/rotor should lean it out. hmm definitely something going on with the rotor though

[Blown88GT]

The basics: cap, rotor, wires, plugs.
I was thinking 1 wire is not making good contact. Don't forget the center wire to the coil.

I have an MSD Pro Billet. Seems just as good as OEM. Ignition box is 1st gen Crane Hi-6 & Crane PS-91 coil.

[5.0Thunder]

The wires are all new Firecore's, in good shape with protector sleeves. Plugs are brand new, cap and rotor are a couple years old, maybe a few hundred miles on them.

Obviously something is wrong with the cap and rotor if providing the proper contact between the rotor and cap post is making such a drastic change. Does it make sense that better spark energy would burn more fuel and make the wideband show rich?

[rickb794]

Careful there, the wideband does not measure fuel, it measures the difference of O2 content in the exhaust in relation to the atmospheric O2 content.

The gauge (or TS) translates that into AFR for human consumption.

Which can be confusing as a misfire will cause indicated AFR to be lean, when an over-rich mixture is causing the misfires.


In the past I have used TFI modules for an input (using just the PIP signal source) and use the MS native output to fire what ever.
This provides a high level signal that is less prone to noise for the MS input, the downside is that you are limited to a basic trigger.
An EDIS module is just as evil as a TFI, no gain going in that direction.
However (separately) a EDIS coil and the EDIS crank wheel and sensor are excellent devices to pair with an MS.
The 36-1 EDIS wheel provides the MS with greater data to more accurately determine crank position. (and opens the door to wasted spark)

NOTE : there have been reported interference issues with low resistance plug wires (no matter what marketing terms are associated with them)

[5.0Thunder]

I definitely like the idea of using a 36-1 crank trigger wheel and an 8 post (or two 4 post) coil pack for accuracy but just haven't found the best way to implement this yet. Haven't seen a simple bolt on trigger wheel kit for under 300 bucks, which blows my budget.

So understanding that the wideband analyzes the ratio of atmospheric o2 to exhaust o2, does it make sense that stronger spark would burn more of the available fuel and show a richer AFR on the gauge?

Just trying to figure out why fixing the distributor rotor would make the idle pig rich. I'm going to adjust the fuel table and see if this cured the misfire.

[Laminar]

Another idea was grabbing a 36-1 trigger wheel and sensor and wiring the sensor to MS then firing the coil directly, which is most preferable of all but then I deal with the pains/expense of pulley spacing or balancer milling. There doesn't seem to be a simple bolt on solution for this as far as I can tell.

Can you grab an Explorer 5.0 pulley/balancer/wheel/crank sensor? It should match your 50oz balance thought I don't know what the pulley spacing is. Explorer accessories are compact.

Here's another solution

[Blown88GT]

...Can you grab an Explorer 5.0 pulley/balancer/wheel/crank sensor? It should match your 50oz balance thought I don't know what the pulley spacing is. Explorer accessories are compact...

IIRC, he has a supercharger which they usually combine into 1 dual pulley with the serpentine pulley. He'd have to put the toothed wheel on the outside, so as not not mess up the pulley alignments. Then it would be too close to the fan.

I have the same problem. The only way to fit on a Fox body is to remove the A/C condenser & move the radiator forward.

[5.0Thunder]

Another idea was grabbing a 36-1 trigger wheel and sensor and wiring the sensor to MS then firing the coil directly, which is most preferable of all but then I deal with the pains/expense of pulley spacing or balancer milling. There doesn't seem to be a simple bolt on solution for this as far as I can tell.

Can you grab an Explorer 5.0 pulley/balancer/wheel/crank sensor? It should match your 50oz balance thought I don't know what the pulley spacing is. Explorer accessories are compact.

Here's another solution

The spacing between exploder and mustang is different so I can't use that pulley, though It would nearly be more cost effective to convert pulleys at this point. lol

...Can you grab an Explorer 5.0 pulley/balancer/wheel/crank sensor? It should match your 50oz balance thought I don't know what the pulley spacing is. Explorer accessories are compact...

IIRC, he has a supercharger which they usually combine into 1 dual pulley with the serpentine pulley. He'd have to put the toothed wheel on the outside, so as not not mess up the pulley alignments. Then it would be too close to the fan.

I have the same problem. The only way to fit on a Fox body is to remove the A/C condenser & move the radiator forward.

Not to confuse you all, but this is my turbo car. My blower car uses an MSD VR dizzy with internal reluctor with direct coil fire coming from the ECU. Both cars are on MS2 and I've asked questions about both so I know it can be a pain to remember.

From the looks of it, this trigger wheel from DIYautotune won't "just mount up" to a SBF balancer. I think the hole in the middle is far too small.
https://www.diyautotune.com/product/6-3 ... 7bc1c77d8b

There's some dude on ebay selling trick trigger wheels for a variety of applications so i messaged him to see if he had anything. The $400 holley setup is about the only thing that appears to just bolt right up, though it still spaces the crank pulley out a tad.

[Blown88GT]

I am confused, didn't know you had 2 cars. Why don't you add them to a signature?
If it's a pain for you to remember how do you expect me to remember?
I can barely remember what I have.

The trigger wheel says: "1/2″ diameter center hole (with plenty of room to enlarge it for larger crank bolts)"
How big a hole does it need?

The Q&A's say "...if you need to bore it out for a larger size than a typical crank bolt diameter, we recommend using one of our unslotted trigger wheels instead."
https://www.diyautotune.com/shop/sensor ... er-wheels/

[5.0Thunder]

I am confused, didn't know you had 2 cars. Why don't you add them to a signature?
If it's a pain for you to remember how do you expect me to remember?
I can barely remember what I have.

The trigger wheel says: "1/2″ diameter center hole (with plenty of room to enlarge it for larger crank bolts)"
How big a hole does it need?

The Q&A's say "...if you need to bore it out for a larger size than a typical crank bolt diameter, we recommend using one of our unslotted trigger wheels instead."
https://www.diyautotune.com/shop/sensor ... er-wheels/

Lol sorry about that. Fixing it..

I didn't want to bore it out and risk losing concentricity in the wheel. I know the gap between the sensor and teeth is somewhat critical.

I did some more digging and happened to find these.

http://www.clewett.com/index.php?main_p ... 1nqppgkfq6

https://electromotive.com/our-products/ ... ger-wheel/

First one is 200 with a sensor mount, second is 100 without the mount. I can weld up a mount in no time for free so I'm considering option 2 for 100 bucks. Still more than I wanted to spend when these are on the market...
https://www.ebay.com/itm/OEM-NEW-Ford-C ... Dk&vxp=mtr

With a trigger wheel, I can use the dizzy for spark distribution in the mean-time then grab an explorer cam sensor and run CNP or 4-post coil packs when I get MS3.

[rickb794]

You can get an OEM 5.0L 36-1 trigger wheel sensor and front cover,
The sensor and trigger wheel are on the back of the balancer so not in the way of any accy crap and won't get hit if you pitch a belt.

[Raymond_B]

I am confused, didn't know you had 2 cars. Why don't you add them to a signature?
If it's a pain for you to remember how do you expect me to remember?
I can barely remember what I have.

The trigger wheel says: "1/2″ diameter center hole (with plenty of room to enlarge it for larger crank bolts)"
How big a hole does it need?

The Q&A's say "...if you need to bore it out for a larger size than a typical crank bolt diameter, we recommend using one of our unslotted trigger wheels instead."
https://www.diyautotune.com/shop/sensor ... er-wheels/

Lol sorry about that. Fixing it..

I didn't want to bore it out and risk losing concentricity in the wheel. I know the gap between the sensor and teeth is somewhat critical.

I did some more digging and happened to find these.

http://www.clewett.com/index.php?main_p ... 1nqppgkfq6

https://electromotive.com/our-products/ ... ger-wheel/

First one is 200 with a sensor mount, second is 100 without the mount. I can weld up a mount in no time for free so I'm considering option 2 for 100 bucks. Still more than I wanted to spend when these are on the market...
https://www.ebay.com/itm/OEM-NEW-Ford-C ... Dk&vxp=mtr

With a trigger wheel, I can use the dizzy for spark distribution in the mean-time then grab an explorer cam sensor and run CNP or 4-post coil packs when I get MS3.

Be sure to measure the thickness of those wheels because you'll have to take that material off your balancer. Also be careful of the Holley setup, the wheel is like .250" thick! The ones you listed look to be .125". If you do not want to spend that 100.00 shop around for a machinist to bore out the DIY wheel. Maybe you can get a decent deal. You're right it needs to be pretty true. Also when you figure out how you want to mount the sensor don't forget about how you'll mount up your timing pointer if you use those mount points. I've been through all this, there's no real easy solution if you run an aftermarket balancer.

[Blown88GT]

You can get an OEM 5.0L 36-1 trigger wheel sensor and front cover,
The sensor and trigger wheel are on the back of the balancer so not in the way of any accy crap and won't get hit if you pitch a belt.

I think it's easier said than done. Searching around, I found this thread on our forum.
http://www.msextra.com/forums/viewtopic ... 71&t=54437

[Raymond_B]

To be clear, finding a sensor and a timing cover with the mounting bolts are no problem. I have two brand new timing covers from a later model Ford truck with sensor mounting holes that would use the "normal" truck front dress and I *think* it would be OK on a Fox body as well.. It's the wheel and its mounting that fouls everything up.

Picked two of these up from Ebay.

[Drew442]

1998-2002 Ford Falcon from Australia has the VR mounted to the timing cover, 36-1 wheel on the balancer, two 4 post coil packs and cam angle sensor with oil pump drive.

Everything you you need for sequential injection and wasted spark and all with factory parts.



Sent from my MI 5 using Tapatalk

[5.0Thunder]

1998-2002 Ford Falcon from Australia has the VR mounted to the timing cover, 36-1 wheel on the balancer, two 4 post coil packs and cam angle sensor with oil pump drive.

Everything you you need for sequential injection and wasted spark and all with factory parts.



Sent from my MI 5 using Tapatalk

Nice, is water pump rotation counterclockwise?

[Laminar]

1998-2002 Ford Falcon from Australia has the VR mounted to the timing cover, 36-1 wheel on the balancer, two 4 post coil packs and cam angle sensor with oil pump drive.

Everything you you need for sequential injection and wasted spark and all with factory parts.

That's literally the exact same setup as the 5.0 Explorer.