MY 97 has developed a new feature.

The engine tends to cut out, momentarily, while cruising on uneven roads. My initial guess was the CPS, but this was changed to no avail. The behavior seems similar to an electrical disconnect. Typical scenario is as follows:

Cruising on smooth freeway: no problem. Freeway turns rough. Vehicle bucks, WTS light comes on. Driver releases throttle. Locked torque converter drives engine anyway. Driver reapplies throttle and engine resumes.

While this does seem like an ignition reset, I think it is not in the ignition circuit because the odometer does not revert to the standard setting, it stays on the trip setting if it was put there. Also the cruise control set point is not lost. Having said that, there might be multiple ignition circuits, and I'm only losing one which kills the engine.

There are cases where the 'outage' is longer or the torque converter is unlocked and the engine stalls, requiring a restart.

Any ideas where to start looking? I just replaced the CPS, and the issue returned within 35 miles (30 were on smooth roads anyway).

Not sure if it's related, but I got a refusal of the torque converter to lock up once today. Drove 10 miles till I couldn't tolerate the high tacho reading. Checked ATF level (was fine). Restarted and the issue vanished. Hasn't come back since, though the engine cut out has.

Rory

 

You might have several issues happening. I had similiar problems (and still do now and then). Folks here have suggested there might be a problem in the Vehicle Speed Sensor (VSS) wiring.

I've replaced the VSS several times and it seemed to help, but the condition would return.

If your VSS is good and the wiring is not grounding out, you might try removing and wiping off the VSS. Don't use any solvents or anything; just wipe it off and reinstall it in the rear differential.

While you're under the truck, check the electrical connections on the transmission, if any, for looseness and overall condition.

A worse-case scenario might be the Progammable Speedometer Odometer Module (PSOM) might be going bad.

Check the simple stuff first, let us know how it went, and we'll deal with it at that time.

Are you setting any codes? Knowing the codes would help out a lot.

 

I would replace the CPS again. They have been known to be bad brand new. It can't hurt for the price. Unplug the batts also to reset the PCM.

These are very typical symptoms of CPS.

 

the problem your having sounds like the same problem im having with my truck at work. it realy acts up when you put a little stress on the engine, like pushing the go pedal a little harder, or when i let out on the clutch and it loads the engine down it will do the one second stall and sometimes buck a little. does your truck do it more when the temps are a little hotter outside than when its cooler?

 

I think you may need to look at your fuel bowl heater. The element inside is probably rattling around. And when it meets the bowl itself, it will try to shut the truck down. Usually it blows a fuse, but it could do what you are talking about. If you pull the filter, look down in there. There is a wire sitting on 3 lead pucks. Those pucks normally come loose and allow the heater wire to contact the bowl. Most people just unplug them and forget them. You really only need it if you are in really cold climates.

 

Good suggestion duck.
That sounds very plausible.

 

Thanks for all the replies.

I think the issue is electrical, so I'll follow up on things like the VSS, trans connections and the fuel bowl heater. I like the VSS theory because it is unsprung mass and so it gets the harshest road inputs. That siad, I need new shocks all around, so I can easily believe engine end connection issues as well.

J tate: I think we are having different issues. My problem seems completely unrelated to throttle position. So far as temperature goes, ambients here are always cold right now, but the engine itself is warmed by the time this happens - just a matter that by the time I get to speed on bad roads, the engine is warm.

About the CPS: Is there any tech detail on this thing? I can see it's a 3 wire sensor, so I figure 1 pin is regulated power (5V, 12V, or such), one pin is ground, and one pin is a pulse signal. Does anyone know which pin is which? I'd put the signal on an ocsilloscope and see if it has dropouts (plus, it looks like a convenient point for a homemade tacho tap).

thanks,

Rory

 

The vss won't cause you engine to hiccup unless you have the cruise control on.

TPS info:
https://www.ford-trucks.com/forums/5...ge-on-tps.html
A good scanner will show the TPS and CPS at work. My AE does anyway.

CPS info:
Signal Functions
The camshaft position (CMP) sensor is a Hall-effect type sensor that generates a digital frequency, as windows in a target wheel pass through its magnetic field. The frequency of the windows passing by the sensor as well as the width of selected windows allows the powertrain control module (PCM) to detect engine speed and position.

 

Cuda_Jim,

Perfrect. Exactly what I was looking for. Thanks,

Rory

 

rubberduck i think you might have stumbled apon something with my problem. just yesturday i posted another thread about the fuel in the fuel filter being scalding hot, and is it supposed to be that darn hot. is there a relay that turns the fuel element off when it reaches a certain temp are it just heats all the time.what is your thoughts on this issue?

 

The fuel heater is self regulated and contained within the element. If the heater element is shorting then the fuel may be getting too hot. You can unplug the connector on the side of the fuel filter bowl. Use a thin blade screwdriver. Pry it slowly so the seal doesn't get hurt, leaks.

It's the squarish looking plug on the driver side of the bowl right under the fuel pressure test port.

 

Hi Jim.

I see two connectors in this picture. The upper one has a single red (in my truck) line. The lower one, a single black (or dark something) line. Which is the fuel heater, and what is the other one?

I think this is the problem as #22 fuse blew out the other day.

Rory

 

in that pic is the upper one (spade type).

 

Here is a pic (stolen from BlueMule) with 3 connectors, the middle one is which we are talking about.