Cruise Control Quandry

Cowcatcher · **Posted:** Fri Jul 14, 2006 1:19 am

It may be too focused on the job still at the end of the day, listening to the news on the radio, oldtimers, or a real cruise control problem. Just in case it is the last let me describe it and see if any of you have the same problem.

The last few nights I have had to take an alternate route home which involves 5 or 6 miles of Interstate driving at 60 MPH. Last night I got on the freeway, pushed up to 65 to get TC lock in 5th then settled down to 60 and set the cruise. After a couple of miles I noticed that I seemed to be closing on some traffic pretty fast and when I look at the speedometer I was doing 70 MPH. I figured I must have set it wrong in the first place or perhaps tapped it up a little without thinking about it as I tried to blend in with other traffic. Tonight the same routine and totally forgot about last night. Again I noticed I seemed to be going a little fast after about a mile and the speedometer says I am doing 65 and it seems to be gaining.

I will test it tomorrow and perhaps over the weekend to see if it creeps again, and I do need to schedule a routine service next week but have any of you experienced this?

Thanks in advance.

alljeep · **Posted:** Fri Jul 14, 2006 7:13 am

I have not had this happen, but in some speed ranges, just one bump/click of the accel button on the cruise control can result in as much as 5mpg gain.

RFCRD · **Posted:** Fri Jul 14, 2006 8:29 am

alljeep wrote:

I have not had this happen, but in some speed ranges, just one bump/click of the accel button on the cruise control can result in as much as 5mpg gain.

Heavy cruise control user, been seeing the same thing recently. Most of the time I have to hit "cancel" and reset the speed. From what I have seen from other electronic Detroit Diesel products, most likely a software glitch or a dirty signal from the vehicle speed sensor. Will usually throw a CEL and drop out of cruise if a VSS completely fails (common failure on DDEC engines). Think your Jeep dealer will figure out this one??? NOT.

alljeep · **Posted:** Fri Jul 14, 2006 8:39 am

RFCRD wrote:

Think your Jeep dealer will figure out this one??? NOT.

I cringe at the thought of ever having to bring it in for any repair. I won't take it in for a noise - chasing a noise is like chasing a ghost and only leads to more trouble. Only if it is barely running for whatever reason will I ever relent.

RFCRD · **Posted:** Fri Jul 14, 2006 8:55 am

alljeep wrote:

RFCRD wrote:

Think your Jeep dealer will figure out this one??? NOT.

I cringe at the thought of ever having to bring it in for any repair. I won't take it in for a noise - chasing a noise is like chasing a ghost and only leads to more trouble. Only if it is barely running for whatever reason will I ever relent.

The last time I had this problem the DDA guys couldn't even figure it out (with an active CEL). I finally crawled under the bus and found a corroded ground on the VSS. Unfortunately with a warranted engine, an active CEL, and without a Prolink just don't have much choice but to start with the dealer shop.

Cowcatcher · **Posted:** Fri Jul 14, 2006 9:16 am

Thanks folks. I have not had a cruise ever do this before. Glad its not my mind going. :lol:

RFCRD · **Posted:** Fri Jul 14, 2006 9:57 am

Cowcatcher wrote:

Thanks folks. I have not had a cruise ever do this before. Glad its not my mind going. :lol:

Just one of the quirks of "run by wire" technology. Get used to it, gassers will do it too before long. Just wait till your throttle position sensor shorts and it takes off like a rocket.

DarbyWalters · **Posted:** Fri Jul 14, 2006 10:15 am

Are you listening to some Frank Sinatra and tapping your right thumb to the music...

Try holding down the "CANCEL" until you reach the speed you want and then hit "SET" and see if it stays there...

Then turn on Nancy Sinatra...your right thumb will halt

GilaMonster · **Posted:** Fri Jul 14, 2006 2:17 pm

I have not noticed the cruise control changing my set speed, but I have had my cruise control turn off (as if you hit your brake pedal or cancel button) when going through fairly steep dips in the road. There is this one road on my commute that it does this on regularily one way, but not the other. Strange.

jinstall · **Posted:** Fri Jul 14, 2006 2:32 pm

Cruise does not work past 140kph so I have no use for it except when towing a trailer.

Cowcatcher · **Posted:** Fri Jul 14, 2006 3:51 pm

DarbyWalters wrote:

Are you listening to some Frank Sinatra and tapping your right thumb to the music...

Try holding down the "CANCEL" until you reach the speed you want and then hit "SET" and see if it stays there...

Then turn on Nancy Sinatra...your right thumb will halt

http://www.internationalpolka.com/

bhysjulien · **Posted:** Fri Jul 14, 2006 6:15 pm

jinstall wrote:

Cruise does not work past 140kph so I have no use for it except when towing a trailer.

How fast do you drive your Libby? What's the mileage like at high speed? Pleas respond in MPH for the metrically challenged.

Desert_Busa · **Posted:** Sat Jul 15, 2006 12:06 am

Google 140kph to mph

140 kph = 86.9919669 mph

Blocks get less then optimal mpgs at that speed

bhysjulien · **Posted:** Sat Jul 15, 2006 12:15 am

I'm very curious about how fast he is cruising on the Autobahn.

oldnavy · **Posted:** Sat Jul 15, 2006 7:03 am

jinstall wrote:

Cruise does not work past 140kph so I have no use for it except when towing a trailer.

I have had ours set on 90 mph by just useing the excellerate button. Our VW's TDI's would always to max speed on CC and so does my Dodge Magnum. Funnly thing with the Magnum is it will go past the limiter speed on CC without a problem and just this past Thursday I had it set at 115 mph blowing the cobbs out as it were and no it was not close to red line. Top end was 127 mph and without CC it is limited to 115 mph, the top end was not quite the 6,500 red line, just hp/tq vs weight and drag.

retmil46 · **Posted:** Sat Jul 15, 2006 11:31 am

RFCRD wrote:

alljeep wrote:

I have not had this happen, but in some speed ranges, just one bump/click of the accel button on the cruise control can result in as much as 5mpg gain.

Heavy cruise control user, been seeing the same thing recently. Most of the time I have to hit "cancel" and reset the speed. From what I have seen from other electronic Detroit Diesel products, most likely a software glitch or a dirty signal from the vehicle speed sensor. Will usually throw a CEL and drop out of cruise if a VSS completely fails (common failure on DDEC engines). Think your Jeep dealer will figure out this one??? NOT.

Hmmm, there is a TSB, think it applies to KJ's in general, concerning the speed sensor on the rear diff. Seal may go bad and the sensor become contaminated with axle fluid. Been too long since I looked at it to remember if it had anything to do with a flaky cruise control.

RFCRD · **Posted:** Sat Jul 15, 2006 12:20 pm

retmil46 wrote:

RFCRD wrote:

alljeep wrote:

I have not had this happen, but in some speed ranges, just one bump/click of the accel button on the cruise control can result in as much as 5mpg gain.

Heavy cruise control user, been seeing the same thing recently. Most of the time I have to hit "cancel" and reset the speed. From what I have seen from other electronic Detroit Diesel products, most likely a software glitch or a dirty signal from the vehicle speed sensor. Will usually throw a CEL and drop out of cruise if a VSS completely fails (common failure on DDEC engines). Think your Jeep dealer will figure out this one??? NOT.

Hmmm, there is a TSB, think it applies to KJ's in general, concerning the speed sensor on the rear diff. Seal may go bad and the sensor become contaminated with axle fluid. Been too long since I looked at it to remember if it had anything to do with a flaky cruise control.

This could be possible but most of the time when the VSS is going bad, cruise will work but won't hold steady speed. Sometimes will even buck/stumble, actually feels similiar to the CRD stumble after hard acceleration. Cruise will remain engaged unless the probe fails which should throw a CEL and in theory shut down. This situation acts more like a software glitch (computer not counting the correct number of switch strikes). Have even seen a sticky switch cause the same thing (that turned out to be a Pepsi issue).

Cowcatcher · **Posted:** Sat Jul 15, 2006 12:36 pm

You know, I have only had this happen twice and it was in exactly the same place at the same time of day and the same traffic conditions. That is really strange. I am an old RF guy and since a lot of this stuff is electronic perhaps a little RFI is to blame.

RFCRD · **Posted:** Sat Jul 15, 2006 12:51 pm

Cowcatcher wrote:

You know, I have only had this happen twice and it was in exactly the same place at the same time of day and the same traffic conditions. That is really strange. I am an old RF guy and since a lot of this stuff is electronic perhaps a little RFI is to blame.

This is a well documented issue with DDEC engines when installed in trucks using strong radio equipment (such as a municipal trucks). Key the mic or simply be driving near the radio transmitter and the engine dies from RF interference. I was cautioned about mounting a CB radio on the side panel of the drivers area of OTR coaches because it could interfere with the electronic equipment was mounted on the other side of the panel.

Cowcatcher · **Posted:** Sat Jul 15, 2006 1:03 pm

RFCRD wrote:

Cowcatcher wrote:

You know, I have only had this happen twice and it was in exactly the same place at the same time of day and the same traffic conditions. That is really strange. I am an old RF guy and since a lot of this stuff is electronic perhaps a little RFI is to blame.

This is a well documented issue with DDEC engines when installed in trucks using strong radio equipment (such as a municipal trucks). Key the mic or simply be driving near the radio transmitter and the engine dies from RF interference. I was cautioned about mounting a CB radio on the side panel of the drivers area of OTR coaches because it could interfere with the electronic equipment was mounted on the other side of the panel.

I worked for the Land Mobile side of Motorola and in the late 80's we started having problems with Ford products crapping out when you keyed a 100 watt mobile radio in some frequency bands. The culprit? The unshielded electronic ignition module in the Fords. Who made it? Motorola! Go figure!!!!

There is a telco switch right next to the freeway where this has happened. I will look for microwave the next time I drive by. Last night I set my cruise a little farther down the freeway due to traffic and it didn't happen.

Cruise Control Quandry

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