Engine cuts power and PATS light come on

[Tex]

On my 3L, I've been having an issue where occasionally (or almost always some times...) my car completely looses power. I first noticed it when I went autocrossing last week at about 5500+ RPM in second gear. It happened a few times and it would just be like shutting the car off, the power was GONE, not just a little hesitation. Of course, I would stick the clutch in immediately, and it would come back. Every time it happens, the PATS light on the dash comes on for a few seconds. At first I thought that it only seemed to happen when I was in second gear and heavy on the throttle, but it did it for me in first, second, and third gear earlier today. Each time it seems like it was at about 3500-3700 RPM. I drove this car all last week and had no problems except at the autocross, and now today it's happened about 10 times. I have a feeling that it has something to do with PATS, but I really don't know where to start. I have an xcal, but I don't know how to use it to datalog. It doesn't feel like it did in my 2.5 when the fuel pump was dying, and this one already has an FSVT pump installed. Any input is appreciated.

 

[Ray]

Unplug your TPS when it starts happening. See if it stops.

Your problem has NOTHING to do with PATS. PATS isn't involved once the car is started.. it is only flashing because it lost power and is "re-testing" itself as it does when you turn the key on.

The problem is due to a loss in your VREF signal, only a few components use that signal. The TPS is one of those.

Anyway.. your problem is likely either a wire or a connector, or even the component itself (that the connector plugs in to). This is why unplugging the TPS may fix it. If it does, inspect the wiring, the connector and the TPS pins themselves. Maybe a little light sanding to remove corrosion or anything to cause arcing, etc.

Edit: If you search, you'll see I've had this same problem.. started out "cutting" once a week.. then once a day.. then it would go in fits of either 2 rapidly, or up to 20 or 30 in a row. Finally, it got to be that any time the car was running, it was doing it. Most of the time it was so "rapid succession" that the PATS light would "stay" on..

Symptoms I got:
tach would dive toward 0 for a split second.
CEL would "flicker" (though sooooo faintly and quickly that in the daylight it was hard to see)
PATS light would self-test for one second per "hiccup"
injectors/fuelpump/etc all cut out causing a HUGE jolt, especially if you were WOT when it did it! lol

It "seemed" to happen more when I was heavy on the gas, or WOT. Though after a while it happened all the time.

 

[Tex]

Yeah, I saw that about your TPS the other day when I searched. I will check it out. My PATS light does not flicker though; it comes on plain as day for 5-10 seconds. Would it make any difference that I have a Mustang GT TB? Also, I know that I have a somewhat loose positive battery connector. It is loose, but not to the point where it would be coming off. Anything relevant?

 

[Ray]

My PATS light didn't "flicker".. the CEL flickered. the PATS would illuminate for 1 second per hiccup.. (the normal prove-out test period)

when it got really bad the PATS would stay on for almost a minute, but it was actually just a rapid succession build up of a minutes worth of hiccups.

 

[Tex]

Well, I went out to the car and unplugged the TPS connector. All of the connections look clean and I lightly filed them with a fine file for good measure, but I did find this little beauty here-

I pulled on each end and it still appears to be one piece but I wouldn't think that it could be helping matters at all. I tightly re-taped it for now. Do you think cutting the wire, putting in a crimp connector, and heat shrinking the section would be a good idea? I hope it is something that simple...

 

[Ray]

Well, you could crimp it.. I'd PREFER a soldered connectino with shrink wrap(heat shrink) but a crimp would work, sure.

 

[Tex]

Yeah, the only thing is I left my soldering iron at another house, and I'd have to cut the wire anyways to get the shrink tube on it. I guess I should have thought of soldering it first...

 

[BrApple]

could something like this cause the instrumenat cluster to stop working? I have started getting a P1122 and P1125 recently and this afternoon it happened about 5 times in a row. a restart would fix it. no parts or fuel delivery problems.

 

[Tony2005]

could something like this cause the instrumenat cluster to stop working? I have started getting a P1122 and P1125 recently and this afternoon it happened about 5 times in a row. a restart would fix it. no parts or fuel delivery problems.

I think it could. The TPS signal wire is White and it sends a voltage of 0.53 to 1.27 (according to Chiltons), to Pin 89 at the PCM. If that wire is shorted somewhere, it could cause problems to the Instrument Panel (voltage or hertz signal wise)

 

[Tex]

Ok, so back to my original question- The car was majorly acting up today. Anytime it would hit ~4000, BOOM!, no power. I drove on the highway for about 10 miles to meet up with starjammir and it was even trying to die at a steady 3000 RPM on the interstate. When I got there, we took it for a drive and it was still cutting out, so I took your advice and disconnected the TPS since this was the first time that it was doing this regularly. Presto! The problem seems to be solved. The connections are clean and the wires are in good shape as far as I can see, so does this mean that I need a new TPS?

 

[Ray]

Not really... I unplugged my TPS after about three MONTHS of wire tracing, ignition changing, Pats troubleshooting, battery replacing and ground/positive replacing all over the car.

I stumbled on it from a Joke from Worldtour.. he said "well, hell, unplug the TPS, we've checked everything else" and when it stopped instantly we both dropped our jaws and went "what thaa........"

What did I do to fix it?

haha, I plugged it back in and it NEVER did it again, not even once. Either there was some "gunk" formed across the pins that was conductive, or something, but replacing the connector left me with NO ill-effects. This may happen to you, too.. if not, good luck.

The problem (if it doesn't remain gone) is in the wiring or the connector. While ANYTHING is "possible", I'd not jump on the TPS itself too quickly, though it isn't IMpossible.

Try plugging it back in and see..

 

[Tex]

Well, I unplugged it the other day to check the connector like you told me to, and it got worse after I plugged it back in that time but the car was off at the time, so MAYBE if I plug it in while running...

 

[Tex]

Negative. I took the car to the store with the plug undone so that it could warm up. On the way back, I stopped and plugged it back in while the engine was still running to see if it made any difference. The car will not go to 4000 yet again. I'm going to try replacing the TPS. If that doesn't work, what wires should I be looking at? The foot of them that is exposed from the bundle looks fine.

 

[Tex]

I left the TPS unplugged and it seemed to be running ok for a while (except for the obvious throttle hang). Well, after a few trips, it is STILL cutting power even with the TPS unplugged, but it seems to be more intermittent, not every single time. Is there anything else that I could check that uses the VREF signal?

EDIT: DPFE sensor possibly? :shrug:

 

[Ray]

ProjectSHO says:

On the SVT, Vref is only distributed to the TPS and the DPFE/EPT sensor for the years I checked. The OP didn't indicate what year he has....

This was in response to a thread about the "red led on the dash killing my car"..

You can see my thread "Pats module in use while running" as well.
Search "VREF" for both of these to show up..

 

[Tex]

Ok, I've read about a thousand threads that have "VREF" or "PATS" in them at this point, but this one caught my attention- http://www.contour.org/ceg-vb/showthread.php?t=11594&highlight=vref

Check ALL of your grounds in the engine bay.

under the battery/fuse box
at the firewall on the passenger/center side, everywhere.
check the negative wires that go to the battery, and make sure they aren't loose in the crimped on ring that attaches to the battery.

then... the next time it is doing this, repetitively (if it gets worse and more frequent), unplug the TPS from the throttle body.. I bet it smoothes out and stops.

Ok here goes-

1. I had a loose positive battery connector, but I replaced it wiht a new one that I know is TIGHT and the symptoms got worse acutally.
2. I installed my NPG CAI RIGHT before all of this started happening. This means that I messed around with the fuse box (which was already loose actually) and the massive chunk of wires that run along the fender there. I wouldn't know what to look for really do know if I had disturbed something. :shrug: I'm REALLY thinking that this might have something to do with it.
3. The battery is a Motorcraft and the little window on top is green, and it acts like it has plenty of power. I don't think that there are any problems here.
4. If it was the alternator, I would think that the battery would be dead by now, as this has been going on for close to a week.
5. I know about the TPS (will go looking for a new connector and TPS modlue tomorrow), and the DPFE, but what is the EPT?

About how many grounds are there in the engine bay, and where are they? This is why I HATE anything electrical...

Thanks for any and all help!

 

[Tex]

ProjectSHO says:


This was in response to a thread about the "red led on the dash killing my car"..

You can see my thread "Pats module in use while running" as well.
Search "VREF" for both of these to show up..

Was searching as you were typing and didn't refresh this page. Firefox and multiple tabs...gotta love it.

 

[Tex]

Ok, so the car was stumbling again last night, but not EVERY time, so I went further into the VREF stuff and disconnected the DPFE (that's the box on the side on the block under the IAC and stuff right?). I went to the post office today (~5 mi) and before I left, I cleared the code p0122 (TPS). The car ran completely fine until right before the post office once it finally got up to full temperature (192 according to the gauge), and then the bucking returned, worse than ever. I pulled the fuse box up last night and everything looked alright. I really have no clue where to go from here. The DPFE is unplugged, the TPS is unplugged and REMOVED from the car, and all of the wiring that I can see looks absolutely fine. It actually seems to run great and without a CEL even, until the first time it stumbles, and then it immediately throws the TPS code and won't run for . It's almost like it runs fine until it realizes that stuff is missing. What next? Grounds? Bad PCM? I can try loading the stock tune into it to see if it helps. I won't be able to get to my Haynes manual until this weekend to know where the grounds are. This thing is driving me CRAZY.

 

[Ray]

The PCM utilizes a Vref signal, too, I thought. (maybe its just in some years or maybe I'm just off base here).. Another case (as was the main hypothetical culprit from my situation) is the PCM being bad itself.

 

[Tex]

Flame suite ready- Ok, so a 2000 SVT PCM would be kind of hard to find probably. Could I in THEORY, get an SE PCM and use that instead? I have custom tunes anyways, so wouldn't uploading one of those just overwrite everything anyways? :shrug: Otherwise, could I use a PCM from a different year/code? Just a thought.

EDIT: I have 2 2000 SVTs. How hard would it be to swap the PCM between them to see if that was the problem? Is there any way to test the PCM to see if it is bad?

Further EDIT: Just read post #7 in this thread about somebody trying to run the car without a battery- http://www.contour.org/ceg-vb/showthread.php?t=32918&highlight=PCM
As I stated earlier, the positive battery cable was loose when I got the car even though the clamp was as tight as it would go. I know for a fact that it came off of the post at least once, because when I pulled over to disconnect the TPS, it was off, so essentially I was running the car without that battery hooked up, and that guy said that somebody fried a PCM that way. But, the negative cable never came off, so whatever. I still think that swapping PCMs might be the key to this mystery.