93 TC Lost power whilst driving for 30 secs with no ignition lights on

[ccogan]

I was just driving my 93 TC along the road at about 30 miles an hour and all of a sudden no power from the accelerator. There were no ignition or alternator lights on and no oil lights at all and no check engine light.After feathering the throttle for about 20 seconds it suddenly came back to life again. I still had power steering and brakes but absolutely no throttle.Has any one else had this problem. It has happened to me twice now over a period of 3 weeks.

[bill_s]

First thing that comes to mind is the fuel pump or its power path, which includes the fuel pump relay. Also remember the fuel pump emergency cutoff switch in the trunk (boot in Oz).

If the ECC loses power, the fuel pump power would be cut off (I think), but I don't know if any warning lights would be lit.

Intermittents are tough - if you want to make sure you find the culprit, you have to connect some sort of voltage monitor to various points and wait for the failure to happen again. Or go to a dealer and they'll likely replace stuff (on your nickel) until the problem goes away. I like to know I found the real source of a problem.

Second is the battery power to the injectors - if this opened they all would fail at once.

You really need the Ford "Electrical & Vacuum Trouble-shooting Manual" for your model and year. Its got all the wiring, signal paths and device locations. I couldn't work without it. As I recall mine cost about US$35.

[ January 21, 2002: Message edited by: bill_s ]

[bill_s]

Forgot - the fuel system picking up a large slug of water from the tank will do this too. Happened to me when some runoff leaked into a local gas station storage tank. Barely got home by pouring about a quart of alcohol into the tank. Had to completely drain the tank and flush the fuel system to get the water out.

[Charles A.]

From what you wrote it sounded like the engine did not stall (i.e. it kept running) but you just had no throttle control? That sounds like it wouldn't be a fuel problem -- if those occurred the engine would stall.

What you described happened to me once on an old carbeurated engine when the throttle cable actually fell off! The engine continued to run, just no throttle. I was in the freeway at the time and managed to coast to a stop safely. Putting the cable back on solved the problem.

But on the new cars the throttle itself is electronic. The cable only controls the air into the engine. Fuel is controlled by the throttle position sensor (TPS). So if the TPS quit working momentarily, you could experience the symptom you described. But if this occurred it should have at least set a trouble code.

I'd have the shop test your TPS and related wiring. Good luck!

[bill_s]

I would differ with CharlesA - if the car is moving in gear, the engine will be turned through the transmission even if it isn't producing power. This happens down to 5 to 10 mph if the tranny's normal and stock. This happend to my 92 tc when it vapor locked...

Which brings us to another possibility - my 85000 mile car would vapor lock on a hot day at high speed if the fuel got below 1/4. I may have cured this with a heat shield around the single exhaust where it curves around the gas tank. This problem is possibly the product of a high-mileage fuel pump that's running hot and not pumping like new.

If the trouble codes don't point to your problem, you have to improvise. To see if you are intermittently losing ignition, wrap one end of an insulated wire around the low-voltage wires going to one of the coils and the other end around the radio antenna. Tune around the AM band and you will hear your ignition noise, and this will disappear when the engine dies if that's the problem.

You can monitor the injectors by listening to the other end of a 1/4" ID plastic tube that's taped up against an injector.

To monitor the fuel system, you have to put a pressure gauge on the Schrader fitting on the right-hand fuel rail. You should see 35 to 45 psi depending on engine load.

Setting traps isn't easy, but its the only way you can be certain you have the right fix. Or, if you have lots of cash, you can just replace parts until the problem goes away (you hope).

[Charles A.]

I don' t disagree with anything you've said. It definitely sounds like you know what you're talking about. My confusion was with the wording of his initial post -- did the engine stall/cutout or did the engine continue running but lose throttle control? I realize the former is probably much more common than the latter, but I wasn't sure which had occurred from the way he described it.

I don't doubt the engine would continue turning in gear depending on speed, but he did say he had full power steering and brakes which would seem to indicate the engine never actually stalled. Also, as soon as the engine cuts out multiple warning lights will come on, and he said that didn't happen either. So my guess from what he's said is that his engine never stopped running. That was my only point.

[ccogan]

Thanks for all your ideas. I have more news for you all. I stopped to drop off my friend and the car was running in drive and my foot on the brake,as I went to take off no accelerator.I mean I had no throttle control,you would have thought that someone had cut it off!. I put the gear lever into park and still could not accelerate. I finally turned the engine off, turned it back on and then drove away as if nothing had been wrong.It appears to be some computer problem? It cannot be the cable I don't think as it worked perfectly as soon as I restarted the engine. Where do I start to look?

[bill_s]

Lemme see if I understand this - the engine continued to idle normally but did not change its speed when you pressed the accelerator?

[ccogan]

That is correct.There was no response from the accelerator.Only when I turned the engine off and then restarted the engine did I have throttle response

[Charles A.]

Sounds like you definitely have either a TPS problem or a computer problem. The TPS is a sensor that is bound to go bad eventually, so it might not be a bad idea to just get a new one (depending on the age and mileage of your car).

A bad TPS should set a trouble code, so if it did not then this might indicate a fault with the engine computer. It's definitely electrical.

Good luck!

[TW/92LSC/SE]

Just a reminder for those not aware. When turning Ign. to Run just before starting, check to make sure "Check Engine;ABS;Air Susp.;Low Oil and all other warning lights" come on to verify circuits are working correctly. You could have a bulb burnt out or removed by someone selling a defective car. Diagnostic Codes will then be hidden. ;) ;)

[Charles A.]

Very good point but most of these warnings are part of the VFD cluster on this car so they can't burn out (although segments can certainly wear out over time). But you're right -- when turning the IGN on and before starting, make sure the indicators light up. If not, then there's *another* electrical problem!

:D

[ccogan]

I suspect that the tps that you refer to is the throttle position switch.Where do I find this switch please.
Also am I able to simply plug in another computer from another 1993 TC or can I put one in from a latter model.I was unable to get a superchip for my car as Superchips had no knowledge of my code on the computer and could not provide a generic one. Can I put in a later computer that superchips could chip?

[Charles A.]

On the computer issue, I can't say for sure. There were changes from year to year that could cause some problems. In general, the '93 models were all the same, and the main difference in '93 - '94 IIRC was the dual exhaust option. In '95 there was a new engine computer, new wiring and a new tranny, so don't use anything from '95 - '97.

The TPS is the Throttle Position Sensor. It's located on the throttle body which is under the air inlet hose on top of the engine. I don't have my manual handy so I can't be more specific. BTW if you don't have one I definitely recommend a full set of factory Helm manuals before working on stuff like this. You'll need the body, electrical, and emissions manuals.