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Discussion Starter · #1 ·
Hello,

I have a 1994 essex lx wagon, yesterday I was driving back from a trip up to north cali. I was going at a steady 70mph when all of the sudden the engine stalled. Immediately the tachometer went crazy, it was all over the place it would go down to 0, then up to 4 down to zero up to 3 etc, the check engine light would light up and turn off too.

When I brought the car to a stop on the side of the road I tried restarting it in Parking but it would only turn and turn with the tachometer going up and down as it cranked. I thought about it for about a minute and put the transmission on neutral and it started fine, I am not sure if it was just luck that it started then or that it actually made a difference. I drove back home fine after that. Everything felt normal. :huh:

Thanks in advance.

-Jose
 

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Welcome to TCCA.

Seeing as how it stopped misbehaving, restarted & ran ok when you shifted from P to N, maybe suspect the tranny Neutral/Start, or sometimes called the Transmission Range Selector (TRS) switch, it's a common problem part & given the vintage of the vehicle, it's earned a spot on your suspect list.

If that checks out ok, maybe the distributor, the firewall mounted TFI ignition module & their wiring & electrical connectors pins & sockets.

Maybe consider giving them a thump & wiggle test, to see if you can induce an engine stall.

Let us know what you find.
 

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Discussion Starter · #3 ·
Welcome to TCCA.

Seeing as how it stopped misbehaving, restarted & ran ok when you shifted from P to N, maybe suspect the tranny Neutral/Start, or sometimes called the Transmission Range Selector (TRS) switch, it's a common problem part & given the vintage of the vehicle, it's earned a spot on your suspect list.

If that checks out ok, maybe the distributor, the firewall mounted TFI ignition module & their wiring & electrical connectors pins & sockets.

Maybe consider giving them a thump & wiggle test, to see if you can induce an engine stall.

Let us know what you find.
Will check that out right now, I replaced the TRS a little less than a year ago, I suspected it would be the culprit again. I will check on the other things too though.

Thanks for the help, I will post later on my finds.
 

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I would think that if the problem were with the neutral safety switch (or TRS), it wouldn't crank at all. I think the TRS only provides starter lockout functionality and doesn't affect the ignition system.

I would be suspecting the ignition system here, 100%, especially because of the tachometer activity.
 

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Discussion Starter · #5 ·
I would think that if the problem were with the neutral safety switch (or TRS), it wouldn't crank at all. I think the TRS only provides starter lockout functionality and doesn't affect the ignition system.

I would be suspecting the ignition system here, 100%, especially because of the tachometer activity.
could it be a bad ignition module or maybe bad ignition coil?
is there some sort of test I can do to see if they are the problem besides replacing them (considering that the problem seems to happen at random)
 

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I would suggest the TFI module, just because it's a common failure point (usually when the car is at operating temperature). As pawpaw said, if the car is running, it'd be good to do the wiggle test, see if you can cause any funny business.
 

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Discussion Starter · #7 ·
I should share this just in case it makes a difference. The first time this happened to me (I think it was at about 67k miles) it was during a climb somewhere in Arizona, I think we were at about 4k feet, we stopped for a quick bathroom break at a gas station and when we started driving back towards the freeway about 3-5 minutes after the engine cut off and we were not able to start it for quite a while, this time it was also cranking with the tacho bouncing around and not starting.

This time it happened right after finishing the descent from the mountains at the 5 right after freeway 99. I am wondering if maybe that info will give you guys a better idea of what can be the problem. (I am currently at 72k miles). I am going to do the wiggle test right now.I am guessing the TFI module is by or on the distributor?
 

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Jose, iirc, in another thread, i think pawpaw stated the tfi module on his 94 3.8 essex was mounted high on the passenger firewall, partially hidden under the leaf screen?
 

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Discussion Starter · #9 · (Edited)
Jose, iirc, in another thread, i think pawpaw stated the tfi module on his 94 3.8 essex was mounted high on the passenger firewall, partially hidden under the leaf screen?
I found it, its a bit late right now, gonna test tomorrow. Thank you

Edit: came out to see fireworks display, I tested and wiggling the wires around didnt do anything. Could not reproduce the problem :/.

Edit 2: Been doing some reading now and it seems that if the module heats up too much it will fail and then let the car start after it cools down. So I guess that is due to the fact that during the climb temperature can reach up to the "o" in normal from the temperature gauge. Does the TFI failing also cause the erratic, bouncing tacho?

I also noticed that it seems to be inside a heatsink...does it use thermal compound? if so would it help if I used the one I use for my computer? I think it cooks at around 240c, so if it gets hotter than that I doubt it will help.
 

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Since we have the single coil ignition system, the spark coil, along with the TFI ignition module should be on your suspect list, as your problem smacks of a heat soak problem & the coil breaking down from heat is also a common problem with those parts.

In addition to a hot engine thump/wiggle test on the wiring, maybe consider adding a heat gun or hair dryer to the trouble shoot, in trying to induce the problem & begin with heat to the spark coil.
If your using a heat gun, be careful & don't apply too much heat & melt something.

Let us know how it goes.
 

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It must have been close enough for Jose, because he said he found it!!!!
 

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Discussion Starter · #13 ·
It must have been close enough for Jose, because he said he found it!!!!
Yea it was under the leaf screen, I am going to go to the junkyard tomorrow to see how taking it out will be, then once I know I will take apart mine and inspect for visible damage and then from there decide whether to replace it or just apply new thermal compound.;) Thanks.
 

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Yea it was under the leaf screen, I am going to go to the junkyard tomorrow to see how taking it out will be, then once I know I will take apart mine and inspect for visible damage and then from there decide whether to replace it or just apply new thermal compound.;) Thanks.
Remove the leaf screen fastners, remove the cowl rubber seal, lift leaf screen, loosen the two nuts holding the TFI module heat sink to the cowl.
Remove the two heat sink screws, remove the electrical connector & seperate the TFI module from the heat sink.

Apply heat sink compound to the rear of the replacement TFI module before installing it into the heat sink. Reverse the assy removal steps to reinstall.

Let us know how it goes.
 

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Here is a link to DowCorning 340 heat sink compound. It's a heavily zinc oxide loaded silicone grease, whos thermal conductivity is better than silicone grease alone, so it'll help that TFI module make a better thermal connection to it's heat sink & thus it should operate cooler, which it'll likely appreciate, as it seems to be so persnickety about running hot!!!! DOW CORNING® 340 HEAT SINK COMPOUND
 

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Discussion Starter · #17 ·
Is the thermal compound just dielectric grease, or something else?
From what I read they are different things, personally I've never heard of dielectric grease, I work in the computer hardware field so I just happen to own a lot of thermal compound hehehe.
 

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Here is a link to a range of heatsink compounds with a range of thermal properties, that are better than dielectric grease alone, or the old DC-340 compound, so if you have any of them, or ones like them, they would probably be good choices, just select one that'll fit the enviormential operating conditions & grease away!!!! lol
http://www.dowcorning.com/content/publishedlit/11-1712-01.pdf?

Computers operate at low voltages, so they aren't as sensitive to electrical leakage, like our high voltage secondary ignition system is. So a thin film of silicone dielectric grease inside the spark plug boots & on the external spark plug insulator, can help prevent flash over on wet rainy, or humid days, or those cool wet dewey cold starts & DowCorning has unfilled products for that too!!!!

Let us know how the TFI trouble shoot goes.
 

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Grease

From what I read they are different things, personally I've never heard of dielectric grease, I work in the computer hardware field so I just happen to own a lot of thermal compound hehehe.
Heat transfer compound is usually between metal parts that are screwed or clamped together. They are electrically the same. (there are exceptions) This is to transfer the heat better from the heat maker to the heat sink/fins. Two bare metal parts will only touch in 2 or 3 points making transfer weak. The compound fills the gap and stays put, and has good heat conductivity. No electrical issue involved.

Dielectric is used on high voltage items like spark plug boots and coil towers. It has good electric insulator values and keeps water out and keeps the rubber from sticking to the plastic or whatever. Thermal conduction is not the issue. High temp is.

-chart-
 

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Discussion Starter · #20 ·
Remove the leaf screen fastners, remove the cowl rubber seal, lift leaf screen, loosen the two nuts holding the TFI module heat sink to the cowl.
Remove the two heat sink screws, remove the electrical connector & seperate the TFI module from the heat sink.

Apply heat sink compound to the rear of the replacement TFI module before installing it into the heat sink. Revere the assy removal steps to reinstall.

Let us know how it goes.
That part ended up being a lot harder, maybe it was just the car at the junkyard. The hood wouldnt stay up. Other than that removing it was easy. I've decided to go ahead and replace the part. My Dad reminded me of when we owned an aerostar, it would also stall and we would have to wait for it to cool down for it to start again, but I dont remember it having a heatsink. And it was accessible through the inside of the van hehe.

Might as well be sure I wont get any more problems in case the multiple times it has heat up caused some damage. Is there anything that can be done to prevent it from heating up? maybe I can somehow move it to a place where there is less contact with sun and more contact with air? Or would that place be the ideal one? questions and more questions haha!
 
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