My truck has been getting lousy mileage, around 11 mpg.. As most mechanics know our own vehicles are the last to get worked on! Anyway I was having several problems so I got around to putting it onto My Genisys Scan Tool. here is what I discovered, Hopefully this will help others.

Current problems:

• Cruise control not working. had been intermittant since I got the truck a couple years ago.
• Lousy Mileage down from 15ish to 11
• Speedo bouncing at speed intermittantly @60 +mph

I started with codes and I got the code for Intermittant CPS function, so I will be off to buy one of those tmw at International dealer. Even though the code activated it never showed on the check engine light which is probably why many people have discussed problems related to the CPS without the MIL activated.

What I felt was that the TCC was probably not locking up due to some issue. I thought it was the VSS but putting a lab scope on the sensor wires and reading the Genisys data stream showed normal though I got an occational drop which may be due to the CPS problem as the Cruise and R(r=Rear)ABS both use the CPS signal along with the Rear wheel speed to set and disengage the the system.
Also the scan tool showed that the Cruise control switches were working correctly.

The other thing that jumped out at me was that the (BPA)Brake Pressure Applied indicator showed being ON permenantly even though the brake pedal switch was functioning fine on the scan tool.
Looking at the wiring diagrams I discovered that the BPA is actually a redundant back-up sensor to the BOO Brake On/Off switch. What the BPA does is function to send the same signal to the Computer as the BOO does. they actually splice togather at some point. The BPA swith is a normally closed switch of 12V+ it works by opening the circuit when it detects 5-10psi of brake pressure. It is located on top of the master cylinder. what had happened is that the contacts in the plug at the sensor had corroded and caused an open (like the brake was pressed) circuit continuously. Thus the Cruise thought the brake was always on and therefore would not engage. Also when you depress the brake it stops the TCC form engaging so constant torque converter slippage would lower mileage as well as the Coast clutch getting activated. amoung various other things that happen when you brake.

I have a 300 mile trip to make with my gooseneck trailer to pick up a car tomorrow so I will get to see if the Mileage improves. Plan on installing the new CPS before the trip if it is in stock at the dealer. Not sure if this will fix the speedometer issue or not, I think it may actually be the sender ring on the ring gear cuz changed carriers to add the LS differential and had to grind the new carrier to fit the sender ring so it may not be running a constant distance from the pickup

I will let you all know if this solves the problem.

Vehicle is 96 f250 4x4 PSD
DJ
ASE Master Tech.

 

Nice write-up and great info. Hasn't the BPA sensor has been the subject of a recall for some time now? I've replaced a couple of them just cuz the CC stop working. Now I understand how/why is functions. Thanks

 

What is a CPS, how much do they usually cost, and how do you install it?
Thanks,
Fletch

My Mileage is still 13 after a month of multiple different non alcohol based additives, running B20 biodiesel, and pumping up tire pressure to 55 in front and 70 in rear.
I don't run it hard and I do mostly city driving with some intermittent highway.
I have owned this truck for a month and when I firs got it I changed the oil, fuel and air filters.
No lights on.

Also my water temp. gauge only gets up to the "N" in normal. Is this maybe part of the problem? I am not getting as hot as others b/c of a faster thermostat.

 

I'm getting 16-18mpg when I run 70-80. TEmp gauge always reads 'N' in normal. It used to go midway when I had the stock downtube and climbing a hill. EGT is 625@70 and 675@80(reading at the exhaust manifold). PSI boost is 4lbs at 70-75 and 6@80. Tranny temp is usually about 160 in 100deg. heat. Cooler temps show no reading on the gauge. (3.5" downtube, intercooler, banks turbo housing, Joe's IDM mod, diablo 4 bank 65HP chip(it might be a 50, can't remember)).

CPS is a cam position sensor and when bad will cause the engine to die for no apparent reason when coasting. I just installed a cold air intake and from recent mileage checks I might have picked up 1MPG.

I have owned this vehicle(F250 C/C 4X4 97') since 40,000 miles and it has always gotten the same mileage(200,000 on the odometer now).

What I do notice about this chip is how it affects the TC lock. Everytime I let off the pedal the TC disengauges. When I apply throttle it rev's up to about 2800 and the TC locks. This was an annoying little feature of the chip, but I have gotten used to it. I was under the impression that if I was towing this would not be a good thing. The banks chip I have does not do this.

I have heard of people getting 20-22mpg with this truck(pre 1999). I sure would like to find a way to get this mileage without driving 55! haha. I don't think any of the mods I have done has changed mileage at all with the exception of lately, which is not much. It doesn't matter if I am hwy driving or city.. same mileage. I even towed a u-haul 3000 miles and only lost 1mpg.

I am wondering what is the best way to drive the truck when the computer is 'learning'. I wonder if it will have any effect on mileage?!? I say this because I notice when I switch chips it runs like a dog when I use the banks chip. It was never this way.. but then again I never reset the computer when I installed it from the Diablo chip. When I was first comparing the 2 chips I felt that the Banks was just as good/powerfull as the Diablo. The only real difference between them was the throttle pedal curve. The diablo has a much faster ramp. I get alot more smoke with the Diablo when accelerating on the freeway to gain 5mph. That initial pedal push always emits a puff of smoke then clears. Seems like fuel is being wasted with that programming.

 

the sensor is fine it was the wire harness that was bad.
you could just splice the wires togather ad bypass it completely but u would loose the backup system

 

Well I got 13.6-13.9 MPG pulling a 6500lb gooseneck over the Rockies including a 11,400ft pass going to Winter Park and back have not done an unloaded tank yet but results so far are definitely better with the repairs I did above

 

Most of the guys getting big mileage ( 20-22mpg ) are running sticks not autos. That's one big difference I've heard. Our E4OD's won't probably get super high MPG unless you go 45-55mph.

That redundant switch is the one that was causing all those fires in the F150's and Expeditions. The switch is the same one in our trucks too.

 

1 1/2 years ago, I installed cruise controll on my '96 from what I had learned on this site. (adding the correct horn pad and putting the paper clip in the plug which goes to where that switch would be on the master cylinder if I had factory cruise). I started having problems last fall with the OD light flashing and the truck going into limp mode. Dealership replaced the vss. Didn't fix it. This spring I took it back in and told them to keep it until it was fixed. They said the transmission was slipping-replaced that. In a few weeks, it started again. Replaced pcm, cps, and idm (it threw codes for that so they said they KNEW they were bad. (yeah right)I still occasionally have the same problem and they are at a loss. Could my paper clip in the plug be the culprit of all of my problems? If that switch is tied into all of the things you mentioned, it seems like a bad connection with my paper clip could cause all of my problems. What do you think? Thanks.

 

I hope not! That would be one expensive paper-clip!

 

So who, with and E40D, is getting 16-18 mpg around town? I get 16-18 on the highway only. I get 13-15 in the city.
Fletch

 

Mine always get's 16MPG.. in fact it doesn't even change while on the HWY, until recently. I am up to 18 now driving 75-85mph unloaded. I am confident I could get 20 if I could just lay off the throttle. The help lately was the change to the bullet style air cleaner. Much less smoke as well, especially when 'mashing' it. I towed a U-Haul 3000 miles and still got 15MPG doing 70+.

97PSD F250HD, 4X4 CrewCab, 3.5" downpipe, Joe's IDM mod, Diablo 4 bank chip, K&N cone filter, intercooler(ford factory parts), Delo 400 15-40, Little Blue CPS.

 

IF the cruise control works while the problem is occuring then probably not the paper clip but i would cut and splice those wires to be sure. If you connect a good scan tool Like a Genysis or Modis or a ford factory unit you can read to see the status of your sensors and it will also show you the voltages coming from the cruise control switches. On my Genysis I can display it as a graph and watch to see if any signal drops.

 

This is a classic, You need to find a good Electrical diagnostic technician (like me) heh. I tell all my customers that just because the code is triggered for a bad sensor, it does not mean the sensor is bad!!! There is a whole series of diagnostic steps to follow to determine the true source of the code being triggered. However many shops do not follow these proceedures because they are time consuming and do require some brain power. Much easier to have some parts changing grease monkey keep charging you for labor and new parts as long as you keep paying... Trade magazines are full of these "problem" cars and explain how the problem was finally diagnosed and solved. If you actually want to see some of these "problem" issues being solved from start to finish then attend a VICA Automotive skills competition in your state. Search for Skills USA, VICA or NATEF.

 

Well filled up after running around town empty and got 15.3mpg on one tank and 16.3 mpg on the second tanks which was about half freeway driving. So I am happy about that. Thus if the Torque converter does not lock-up you are loosing about 25% on the fuel efficiency..

 

How do you know? Lately I have been feeling like the tranny isn't kicking in as soon as it used to.

I have 96K on my '97. I don't know how long it has been since the tranny fluid has been changed. It smells okay at best. But it isn't slipping.
Should I drain it. Some of it or all of it?
Thanks,
Fletch