Symptoms of bad TFI module?
 

Well, I finally got my 393 installed and fired it up. It runs, but very rough.

Some of you may remember the difficulty I had with the old 302 that was there. Ran rough as well.

Both of the motors don't run the same, but the way the 393 is running right now, reminds me of the 302, it gargles and coughs, if you raise the RPM it stays consistant, you hear slight popping in the exhaust, u can smell raw fuel in the exhaust...etc.

The only part I can think of regarding ignition that hasn't been changed since I put the 393 in, is the TFI module. I'm wondering what kind of symptoms a bad TFI module will cause? Will it cause an engine to run rough like this?

Mine is on the drivers side fender near the computer.

Also, how much do these modules usually go for? My haynes manual mentioned them being particularly expensive.

mines mounted on the distributor.... I've melted a few in the last 200k miles.
cost like $14 I think, I dunno... I always got mine off old mustangs.
Of course mine never ran rough, just outright dies.
wouldn't hurt to change one out, but I'd be looking elsewhere

Usually with TFI Mods, they either work, or they don't, I don't think theres an in-between, or any symptoms of it going bad...

I had someone else from another forum also say that same thing. So I guess the conclusion is that the TFI module probably wouldn't cause my rough running situation.

I have no freakin' clue whats wrong, time for bed. :-X15

TFI modules typically work, or don't work, because they get saturated with heat and
"baked dead" long before they start acting funny.

If you have a fender-mounted TFI module on a heatsink, then it won't get baked dead, but it can "wear out" and you might get some flakiness in ignition. Essentially, the only real sympton is weak or inconsistant spark, as the TFI module drives the coil as well as provide timing feedback to the EEC from the distributor's "wheel of tabs".

Regardless of location, most of the F and E series trucks have the gray TFI module, and the cars are a mix of gray and black, depending on the car. Using the wrong one doesn't prevent the vehicle from operating, just makes for weaker spark than you'd like.

Rough running doesn't necessarily mean ignition either Justin, could also be a minor vacuum leak. Remember that speed density EFI which the E and F series trucks have, rely on manifold vacuum as a primary sensor to determine how much fuel to apply, so if you've added a lumpy cam that causes oscillations in vacuum, or have a small vacuum leak, or a marginal MAP sensor (or a loose ground that the MAP is hooked to), or the ground strap between the passenger side of the engine and the firewall/fender is rotted, missing, or broken, sometimes you can have rough running situations as well.

I'd try to troubleshoot this by looking for codes first, and see if the computer picked up anything obvious. I have the full code listing on my website, and a "stolen" picture as to what to connect together to get the EEC to spit codes. Essentially jumper the two connectors with a wire, then go inside an count blinking off your check engine light, with the key in the "run" position but the engine not running.

http://www.midimonkey.com/~frederic/f350/eec-codes.html

If the computer found something useful to you, start there. If not, then I'd check vacuum while the engine is idling, to see if vacuum is fluctuating, low, or something along those lines. If you have good, consistant vacuum at idle (which you should unless you have a lumpy cam), then I'd hook a voltmeter to the MAP sensor and see what it is providing to the computer.

While an uncommon problem, my F350 crewcab eats at least one MAP sensor a year. I have no idea why, I've never been able to figure it out, as it's the only sensor that gets "whacked". But it happens often and consistant enough that I keep a spare junkyard MAP sensor in the bedbox "just in case". It never dies in my driveway, always during a 1200 mile trip. I've never heard of anyone else having such a problem, but it's at least something to look at that would in fact effect how smooth the engine runs or not.

O2 sensor would be the next thing I'd look at, but the EEC would flag that for you in it's list of codes that it spits out. The MAP sensor isn't always captured with a code, though I'm not sure why.

Well, the motor is being run on an FMS MAF conversion kit. No tuner aid.

I don't have my ground strap there, so maybe I should attach that.

I don't think I have a rough cam, I shouldn't, the idle RPM didn't fluctuate, the RPM doesn't really fluctuate at all, that is pretty smooth (no wacky RPM).

The only code I got was 85, canister purge valve failure.

I have to go take an exam, I'll check back in a couple hrs.

Well, frederic, I found that 4 of my injectors are probably not firing. I've got spark on all cylinders but noticed the paint on the headers was different on some. 8,6,2,1 don't seem to be getting fuel. I pulled the plug wire on the dizy for 8, 6, and 2, and the motor didn't change at all when doing so (while running). I pulled the plugs, those plugs are dry and don't smell like fuel, and the rich reading I get off my air/fuel gauge might indicate that those 4 cylinders arn't firing, and are just simply firing oxygen into the exhaust stream.

I've gotta find out why those injectors arnt firing.

See, it wasn't the TFI module :D

let me ask a stupid question.... how is the new harness wired? Does 8, 6,2 and 1 share a ground? or are all eight injectors grounded together (or given hot, I think the EEC grounds them, I forget, but you know what i'm looking for.... a common point where they are tied together).

Since the injectors don't seem to be firing, unplug one of the non-working ones. Hook your 12V test light to the connector and see if at idle, the light pulses or is on steady. If it doesn't light at all, the issue is electronic, rather than the injector being an unhappy part.

If you don't have a test light, you can make one by purchasing a screw-in 12V socket for $3 at radio shack, screwing in a 500ma 14V bulb, and putting two wires on the terminals of the socket. Touch the two wires to the two pins inside the injector connector. If you can solder, tinning the ends of the wire makes it stiffer so you can push them into the connector and leave them there while you do your troubleshooting.

It's got a MAF conversion kit, not sure if you're familiar with it, but it gives you a new overlay harness containing 8 injector plugs, and the MAF plug, it has a double sided 60 pin connector that sandwiches between the computer and the original 60 pin connector. I'm not sure how the grounds work, but each injector has 3 wires on it, instead of the original 2. I do have a test light, and I'm going to test the injector wires soon. Good thinking on the grounds, I may have to try and figure out how its wired, not really sure. Do you know where the EEC gets it's ground??

The MAF kit ran my old 302, and it ran the guys' truck who I bought it from...so i duno...

I can also move a fuel injector to another cylinder. Say I swap the #8 and #5 injectors. 5 should be working, and 8 currently doesn't, so if I swap them, and it changes, then bad injector. If #8 cyl continues to fail, then it's not the injector itself.

I'm also having problems getting the KOER test to work...

The KOEO test works fine. I have it setup with a test light, and when trying to perform the KOER test, the light will be on like it should. The book I have gives me instructions using a analog voltmeter, but I'm using a test light instead. It said I should have 12v, I have 9.6 on my digital. I tried to continue with the test anyway, and started the truck. I couldn't see any flashes indicating what cylinder engine it's working with (should have 4 flashes indicating 8 cyl i guess)...but about 5 seconds after i start the truck, the idle drops/changes...and it seems to be playing with the idle as if it's running the test. My book says it should do it's thing, then smooth out (computer suppose to change timing i guess), and flash the bulb to indicate code 10, to snap the throttle open, but i never see that flash. My book says once the test starts, it should be "several seconds" til the code 10, Ive had it going for 2 minutes or so and never see that flash to tell me to stab the throttle...its at normal operating temp too....so for whatever reason I can't get the KOER test to work either.

Here, follow me over to this thread....

https://www.ford-trucks.com/forums/s...44#post2654544

Go to the very end...I just posted my last results.

I seem to have power to each injector, but 6,8,2,1 arnt firing. If I pull the injector plug on #5, the engine will wanna die....if i do that on 6,8,2,1....the motor doesn't change at all when u unplug the injector.

These are brand new injectors too. weird.

How did you cut the old wires?
Since the old harness is still plugged in might you have shorted out some injector signals?
Thats my first impression.
Popa Tim
(edit)
Also, what kit is this, seems that some are Sequential rather than batch so you'll need to make sure the injector order is correct now too.

I've actually never seen the SD to SEQ kit, but the piggy back idea sounds like an easy installation. And here I am repinning connectors :D

Looked at your other thread. And the EEC has multiple grounds...

Pin 20 is the case ground
Pin 40 is the power ground
Pin 60 is the second power ground

The bank-firing speed density computer (your old one) has the injectors wired in two banks, fired off pins 58 and 59. On a 5.8L engine they are grouped like so:

INJ 1 (58) #1, #4, #5, #8
INJ 2 (59) #2, #3, #6,#7

I confirmed the EEC "grounds" the INJ1 & 2 pins to fire the injectors, and the other side off all eight injectors receive +12V power from the EEC power relay.

Both power grounds (40 & 60) are connected together, to black/white wires that are screwed down on the right front of the engine compartment on the fender apron.

The mustang mass air stuff is different as you know...

Pin 12 - Inj 3
Pin 13 - Inj 4
Pin 14 - Inj 5
Pin 15 - Inj 6
Pin 42 - Inj 7
Pin 52 - Inj 8
Pin 58 - Inj 1
Pin 59 - Inj 2

Like with the trucks, they share a common power point (the red wire of each injector connector) which tie together, and go to the EEC relay.

6, 8, 2, 1 are not firing? I looked for overlapping functionality, but didn't see anything obvious. Pin 12 would be connected to the 4x4 enable if you have an E40D. Pin 42 would be connected to the TOT line of the E40D. And 52 connects to SS1 of E40D. This would be in parallel to injectors 3, 7 and 8, but your having problems with 6,2,1 which has no overlap between the wiring diagrams.

I do not understand the 3-wires per injector thing... injectors have two wires.

What is the chance that you have access to a code scanner of any kind... maybe the EEC (A9x?) can help us out here? I don't see any obvious wiring overlaps, all the injectors should be tied to a common point to the EEC relay, and I assumed you checked to verify that the red wire on each injector has power whenever the EEC relay is closed.

Did you test light the injector connectors yet?

You can also try something "insane" like swapping a "bad" injector for a "good" injector. Swap 7 and 8, since 8's dead and 7's good. Just to see. Probably won't solve a thing, but if we get lucky... we have a whole new area of troubleshooting that opened up. I just want to eliminate everything step by step.

Do you have the emissions crap hooked in? Or did you strip it all out (or leave the connectors hanging)?

Did you switch to a MAF style reluctor ring in the distributor when you applied the MAF kit? The MAF computer will want to see the shorter "signature PIP" in order to fire the injectors in the correct order. The batch fire truck dizzy does not have this feature -- all the PIP pulses look the same. Mismatching the reluctors in this way may cause some injectors to not fire...

From your other thread -- if you probe a connected injector on a stopped engine, you should see 12 volts on BOTH pins. One pin gets 12 volts all the time. The other pin is grounded by the computer in order to fire the injector. When the computer is not grounding this pin, then the injector will feed 12 volts across from its input side, and you will see 12 volts on both pins. If you start the engine, one pin on the injector should remain at 12 volts, the other should flash as the computer alternately grounds and does not ground the pin.

If you remove the connector from the injector, and then probe the connector, you will see 12 volts on one side and "0 volts" on the other. What you are actually seeing (on a stopped engine) is an open circuit, with nothing connected to either end of the wire. The injector is not feeding voltage through, and the computer is not grounding the other end.

If you probe a disconnected injector connector on a running engine, you will STILL see 12 volts on one side and "0 volts" on the other, all the time. Without the 12 volts feeding through the injector, that pin will read "0 volts" when the computer is not grounding the injector (because of the open circuit), and it will read "0 volts" when the computer IS grounding the injector (because it pulls it to ground).

The reluctor wheels should be the same between the two, but it sure wouldn't hurt to check. I thought that might be what was giving my trouble with my MAF system, so I checked the wheel, but found that cylinder 1 already had a narrow tooth. I think most newer speed density systems do have this narrow tooth.

All the EEC-IV's have a narrow tooth to indicate cyl 1, regardless of 4,6,8 cylinders, speed density or mass air, car, truck or van.