RV clinic & performance: Straight talk from the TL tech team

Ford Foot Feed

After 35 years working in the computer industry, I never thought I'd be writing a complaint letter about computer software, but here I am! I have a 1999 Ford Super Duty F-250 with the V-10 and automatic transmission. It is a shortbed with the 43:1 rear-end ratio. I've been pulling a 24-foot fifth-wheel trailer and have a 29-foot model on order. This truck has been great in almost every area, much improved over my '88 F-250. But when I'm going downhill with my foot off the gas, and traffic dictates that I should be going just a little bit faster I touch the gas for a second and remove my foot. I expect the rpm to jump up for a second, then settle back down with the truck/trailer going a little bit faster. Unfortunately, the computer in my truck (according to my Ford dealer), wants to conserve fuel or something, and does not reduce the rpm when 1 remove my foot. Instead, it waits about four more seconds before doing so. This results in the truck/trailer combination gaining much more speed than I wanted, and I must immediately jump on the brakes.

My current trailer weighs about 5,500 pounds, and I would classify this behavior as unsettling. My feeling is that with the new 9,500-pound trailer, I'll find it downright scary! To be honest, it seems unsafe. The behavior is easily noticeable even driving solo. The dealer says "the computer program is up-to-date", as though that settles everything. He also says he cannot find any technical bulletins on the subject. Do you have any suggestions, or am I stuck with this?

PETE JACOBSEN

SCOTTS VALLEY, CALIFORNIA

This is an area of drivability that I have been interested in, too. I went to Ford's powertrain engineers for their explanation and here's what they said: "Some assumptions are in order: 1. The customer lives in California so we assume he has a California vehicle, 2. The customer moves the pedal farther than he thinks, when he tries to speed up a small amount going down a hill with a trailer When the customer is going down the hill with the trailer, the throttle is closed, Decel Fuel Shut Off (DSFO) is active and the Idle Speed Control (ISC) is at the lowest possible duty cycle/air f flow When the customer opens the throttle, two things may happen depending on how much the throttle is opened (as stated above, we think the customer moves the pedal farther than he thinks): a. the ISC moves to a higher airflow position called "dashpot pre-position" and b. the injector fuel is turned back on (DSFO turned off). The "dashpot pre-position" is performed to protect the catalyst from over-temperature concerns, to control hydrocarbon (HC) emissions during deceleration and to reduce driveline noise due to clearances/movement. The "dashpot pre-position" is decreased as engine rpm is decreased until it once again reaches the original point when the throttle was closed. A calibrated value for dashpot airflow is also used to determine when DSFO is activated. One other factor that may certainty impact this issue is the fact that this is probably a California vehicle. California vehicles have a more aggressive dashpot calibration due to being certified on the chassis rollers. The way the 1999 vehicle functions is based on the tailpipe-emission hardware it has and the emission-test procedure. In addition, protection of the emission components on the 1999 vehicle requires a more aggressive approach than in the 1988 vehicle. Our testing indicates that the production calibrations are the best balance between tailpipe emissions, vehicle performance and emission component protection (required for in-use emission compliance). We are very much limited by current emission laws and expect to be more so in the future. Without knowing exactly how the customer is driving the vehicle when he experiences his concern, it is difficult to know what to recommend. Again, taking the customer feedback literally and with all the above information taken into account, I would say that a more gradual opening of the throttle by the customer under the circumstances that he is concerned about would help. Or, use lower transmission gears to aid in engine braking during trailer towing while going downhill."

Although there's a little technical jargon, it's straight from the source and explains why new vehicles act the way they do.K.F

Aftermarket Arctic Package

I'm not sure if this is the correct column for this question, but is it possible to install an arctic package in a used fifth-wheel?

D.B.

VIA E-MAIL

* Most RVs that are built with a coldweather setup, in some cases known as an 'Arctic Package," have the extra insulation built into the unit, D.B. There's additional insulation in the side walls, roof and floor, and to add this yourself, you'd need to disassemble the main components to beef up the insulation. That's not likely to happen as it would be very impractical to do so.

That said, there are some items you can add on an aftermarket basis. Double-pane windows are available from many window manufacturers, and you may be able to buy direct replacements that fit right in your existing frames. Likewise, a visit to a homeimprovement store will reveal several types of do-it-yourself "storm windows" that help insulate your windows, either inside or out.

Finally, if your rig doesn't have an insulated, enclosed belly to help keep your holding tanks from freezing, you may be able to figure out some kind of frame and sheathing that includes insulation. This step, and taking care of the windows, are probably as much as you can realistically do.-JJ

OBDII Hassles

I'm the second owner of a 1997 F-350 dualie crew cab with the 7.5-liter gas engine and E40D transmission. The truck now has 28,000 miles on it. Prior to making any modifications, the "CHECK ENGINE" lamp came on twice, and I had to replace two (out of the three) oxygen sensors. After fixing this, my modifications included a Banks TCM module, a MagHytec transmission pan, Thorley headers, a high-flow catalytic converter and a high-performance muffler. Now the "CHECK ENGINE" light periodically comes on (and sometimes goes off)-the codes that come up are P0402 (EGR FLOW EXCESSivE) and P0420 (CATALYTIC SYSTEM EFF BELOW THRESHOLD). There are no driveability issues, and no change in gas mileage when the light is on. I'm not sure if it's related, but the light has never come on while towing my 9,000-pound 28-foot fifth-wheel trailer (even if I'm pulling the two jet skis behind the trailer)-the light seems to come on when the vehicle is running solo and if I'm pretty heavy on the throttle, and then suddenly let up.

I suspect the high-performance catalytic, but the installer checked the unit with a pyrometer and claims it's running fine. My mechanic is puzzled and unsure how to proceed. Any help would be greatly appreciated.

R. BREAULT

CAMARILLO, CALIFORNIA

* Your truck has the second-generation onboard diagnostic system, known as OBDII in the automotive industry. These systems are considerably more sophisticated and more sensitive than the previous generation. They also detect a lot more problems and are the source of a lot of customer visits to repair shops, even with unmodified vehicles. A high percentage of technical service bulletins now are devoted to OBDII problems as well.

The OBDII uses oxygen sensors before and after the catalytic converter and compares the readings. If the catalyst doesn't clean up the exhaust sufficiently, it stores trouble codes and illuminates the "CHECK ENGINE" or malfunction indicator lamp. Low-restriction catalysts generally have less "substrate" material that clean the exhaust than original units do. The "CAT sYSTEm EFF BELOW THRESHOLD" indicates that the aftermarket catalyst's effectiveness is below the required minimum. Temperature testing will tell if the catalyst is working, but won't tell how much it's doing. A technician can also use a scan tool, assuming the oxygen sensors are all working well. However, the only really accurate way to test a catalytic converter's effectiveness is to use an exhaust gas analyzer before and after the converter.

I believe the replacement "cat" is the source of your OBDII problems and recommend reinstalling the original catalyst, at least for a test period. Sometimes one problem will result in more than one code being set. Disconnect the battery after the original "cat" is reinstalled, but prior to road testing, to clear the trouble codes.KF

Cold Weather Storage

We own a 2001 Cardinal fifthwheel. It is a 32-foot triple slide with enclosed undercarriage. It was ordered with the "Arctic Pack" option, which is heated holding tanks on this model.

Because we are not full-timers, but want to use the trailer in the colder months ahead, is having the holding tank heaters on enough to keep pipes from freezing while we are not using it? Generally, we use it on weekends only, so, although leaving the furnace on while we are away is not a comfortable thought, should we have the furnace on at a low setting in addition to the holding tank heaters? Temperatures will drop to the 20s at night at times. Any thoughts on how to keep from damaging the trailer will help.

JIM BELLIS

VIA E-MAIL

Twenty degrees F at night is pretty mild as a winter temperature goes, Jim, but there are still a couple of things you can do to help protect your trailer and its water system. In your case, leaving the furnace on would be a waste of propane, as well as being potentially dangerous in an unmonitored vehicle. As long as the tank heaters run on 120-volt AC house current, they'll reliably take care of the holding tanks and the nearby plumbing, but for pipes in more remote parts of the unit, you'll need some other kind of auxiliary heat.

Some RVers assemble a wiring setup that places two or three low-wattage light bulbs, in the 25- to 40-watt range, in critical areas of the coach. For example, the setup might include three porcelain sockets wired together so the bulbs are placed on the floor in the bathroom up front, in the center of the trailer and out back in the aft-end living area or kitchen. Leave the cabinet doors open where there's plumbing so the warmed air can circulate. The bulbs won't heat the unit enough for comfort, but they'll take the nip off the air and help avoid pipe freeze-up. As a side benefit, the bulbs also help dry the air and avoid mildew buildup.

Alternately, you can install potable RV water system antifreeze, following your trailer's winterizing instructions and the antifreeze label's directions, and not worry about the extra heaters in addition to the tank heaters.-JJ.

Weighty Question

I have a Ford F-250 HD diesel pickup and have a weight question. The sticker shows the front gawr [gross axle weight rating] as 3,965 pounds and the rear gawr as 6,084 pounds. Do I total these two figures (which equals 10,049 pounds) to get the maximum total permissible loaded truck weight? The gvwr [gross vehicle weight rating] shown on the sticker is 8,800 pounds.

A second question, but related to weight, is, when one adds equipment, such as an auxiliary transmission, does this add to the gcwr [gross combination weight rating]? Thanks for enlightening me.

DICK CARLSON

FLETCHER, NORTH CAROLINA

The gvwr shown on the sticker is 8,800 pounds. That is the manufacturer's maximum gvwr, period. The gawr is just that, an axle rating. The gawr, when added together, almost always exceed the vehicle's gvwr and should not be used to determine gross vehicle weight rating.

Vehicle manufacturers set the gvwr and gcwr When owners add equipment, such as auxiliary transmissions, it might increase the amount of weight that the vehicle can tow, but it does not increase any of the manufacturer's ratings. I do not recommend increasing the load a vehicle carries or tows above manufacturer's ratings for safety reasons. Even if pulling power is increased, brakes, tires, suspension and cooling systems must be matched to the load.-KE

Trailer Axle Swan

I'm searching for an article on leveling my trailer by putting the axle below the springs. I think you did this article once. And concerning the axle saddle/ spring perch, does this have to be welded to the axle or is this a bolt-on item?

BOB NETTLES

VIA E-MAIL

* The article in question, Bob, "Increasing Hitch Height," ran in Trailer Life, October 1998, on page 45. Phone (805) 667-4366 to order a copy of the story, which costs $3.95.

The spring perch is indeed a weld-on item. The perch is an important piece that aligns and holds the axle in proper position and prevents the axle from rotating when the brakes are applied. Welding the perch in place is ajob best left to a qualified professional unless you really know what you're doing.-J.J.

To contribute to this column, please refer to "Reader Information" on page 75.

TECHNICAL INQUIRES

Questions of a technical nature may be sent to "RV Clinic & Performance" at the address above or via e-mail to johnston @affinitygroup.com or kfreund@affinity group.com; no telephone calls. Selected letters will be answered in the magazine, but time does not permit individual replies.

Editorial Offices: Trailer Life, TL Enterprises Inc. 2575 Vista Del Mar Drive, Ventura, California 93001; Fax: (805) 667-4484

Copyright T L Enterprises, Inc. Feb 2001
Provided by ProQuest Information and Learning Company. All rights Reserved