RPM RACING WITH CRUISE CONTROL ON

[joey2cool]

Anyone had this problem? I've got a 2010 Ford E-250 V8 5.4L GAS 2WD van. While driving Highway 97 in 100 degree F temps I noticed my RPMs were racing sporatically with the cruise control on. The van maintained speed properly, but RPMs were occassionally going loco for short spurts (big noise made me think a truck was coming along side us). No problems when cruise control turned off. No problems using cruise control later when the outside temps were lower. Should I ignore it or ask the service dealer to check it out? And what exactly should I expect them to check out?

 

[woodbee-SMB]

Anyone had this problem? I've got a 2010 Ford E-250 V8 5.4L GAS 2WD van. While driving Highway 97 in 100 degree F temps I noticed my RPMs were racing sporatically with the cruise control on. The van maintained speed properly, but RPMs were occassionally going loco for short spurts (big noise made me think a truck was coming along side us). No problems when cruise control turned off. No problems using cruise control later when the outside temps were lower. Should I ignore it or ask the service dealer to check it out? And what exactly should I expect them to check out?

When I am in cruise control and I go into a steep hill it will kick into a lower gear to maintain the set speed. So I try to remember to tap the brake to take it out of cruise control just as I am entering a steep hill. Then I take it out of overdrive and it lowers it (what seems to me) like a half a gear. Doing that I can usually maintain 65 mph. As I top the hill I push the resume button.

Woody

 

[Ford_6L_E350]

With a 5.4L engine, it may not take much of an uphill to cause a downshift.

Even if the torque convertor unlocks, the revs don't change much, so it is probably downshifting. You can try to downshift and see if the revs change about the same.

Mike

 

[carringb]

I think the TC unlocks momentarily when the fan kicks on.

 

[joey2cool]

Ok. I mentioned the wrong highway - I was on I-5 between Lincoln and Fresno for several hours when this started happening. The speed was maintained. It was very hot outside. And I didn't notice a grade in the road, but as mentioned there could have been a slight one.

I gather the concensus is it's not heat related and nothing to work my service dealer up about. Please let me know if anyone thinks differently. :l1:

Many thanks for the fast responses!

 

[Ford_6L_E350]

A couple of ideas came to mind:

- was the AC on? I'm going to guess it was on. I wonder if the AC clutch could have slowed the engine down a little and increased revs and the CC downshifted to get back up to speed.

- what were the revs, normal and racing? Are the revs the same downshifting the trans manually?

- What was the coolant temps when this happened. Not the 'gauge' on the dash. It has a big deadband and doesn't move from about 140-230 degrees.

I'd lean towards the first issue. Sometimes the CC is a little retarded and downshifts quickly if the speed drops and the throttle is increased and the incoming air (or engine coolant) temps are high.

Mike

 

[carringb]

This is what makes me think its due to your fan:

big noise made me think a truck was coming along side us

When my fan is fully engaged it'll drown out a Freightliner. The TC unlocks when the fan kicks in so you don't feel the HP loss in your seat.

 

[Ford_6L_E350]

I had the same thought last night. May have been led astray by term 'RPM RACING'. If the rpms are actually racing, see above. If no tach, or the rpms are fairly steady and it is simply the sound then it is most likely the fan cycling. I remember the first time my fan came on I thought the engine was in it's death throes.

Mike

 

[joey2cool]

A/C was on the entire time. RPMs were jumping from 1200 to 1800 or 1500 to 2000 (that's a tough one to remember exactly).

What fan are you two talking about? The A/C fan? I kept it running on low the entire time. The noise I heard coincided with the RPM increasing - when I finally starting looking at it.

I can only tell you engine temps shown on the dash gauge - it was pegged just above the middle of the gauge range (not alarming). Don't know actuals.

 

[Ford_6L_E350]

Ok. Since the revs were actually increasing on the tach, we can ignore the fan (engine cooling fan is very loud when it comes on).

Next time you are on the road at speed you can manually downshift and see if the revs approximate what you noticed. It probably will be similar. That would mean your van was downshifting. For whatever reason, the Engine controller decided it needed to downshift. It could be a combination of temp, load (pushing a big van through the air and the AC on), wind and who knows what else that caused the downshift, but it sounds like it happened.

It probably only happened with the CC on because the CC uses bigger throttle changes to get back 1-2mph than most drivers will use on their own. If you are close to downshifting, it is not uncommon for the CC to force a downshift that really isn't needed. That is one reason why CC will lower you mileage compared to careful manual throttle use.

Mike

 

[joey2cool]

Sheesh. You just broke another myth I always believed cruise control got me better gas mileage. I might have to change my bad habits now. :a6:

What you're saying makes perfect sense. The Ford owners manual says to downshift if you notice rapid shifting (i.e., throttle searching). Guessing putting it into overdrive when above 55 mph isn't bad for it, but definitely takes a bite out of the mileage. Sooo, turning off CC sounds like a better option when that happens.

Thanks Mike!

 

[Ford_6L_E350]

On flat, level ground CC may increase mileage. In hills, even small ones, CC really hurts my mileage.

Going downhill, it lets speed come up - if you're not watching and a radar unit is on that hill. Then, when the next hill starts up, first the speed comes down. After the road is going up, then the speed drops enough for the CC to apply throttle - but the speed has dropped and the road is rising - so it applies alot of throttle (tanking the mileage) causing downshifts to get the speed back up and to maintain the speed.

Driven manually, I watch hills. On the downside I let the speed come up some, but not into ticket territory, and before the road starts back up I apply a little throttle to keep the speed without lowering the mpg's. I watch the MPG reading on my ScanGauge to find a good throttle position. I try to keep the instaneous mileage at or above 10 mpg, even if I have to let the speed fall. On the highway I don't let the speed go below 55. On a series of moderate hills I can keep the mileage the same as on a flat level road. Bigger hills that require more throttle to keep the speed up still drop the mileage, but not nearly as much as CC does.

Mike

 

[Ultrasport12]

In my 2008 V-10 the cruise is really very steady but that being said it does all kinds of shifting and such to do so. As you go up a hill it will shut off the overdrive as soon as it slows 1/2 MPH and then it keeps shifting down to maintain the speed it is set at.. Going down a hill it also kicks down more and more so it does not speed up over the set speed if at all possible...The normal highway RPMs for me is 2,000 at 70 MPH sometimes going up or down the hills on I-5 it can be as high as 4,000 trying to hold the speed steady and that makes a lot of noise, sometimes you think it will never shift back up but it always does just not as soon as you thing it should. I also think that as the trans and coolant temp goes up while climbing a hill the radiator fan does engage a bit more and that also makes more noise as others have mentioned especially if the RPMs are higher then you hear both the engine and the rad fan noise more.

It is normal for the RPM's to change quite a bit (on hilly roads) with any modern multi speed/overdrive transmission with the cruise control on but in some vehicles it is much more noticeable than others.

When you drive with the cruise off your speed changes more than you think on hills and your right foot controls the shifting (or lack of shifting) much more, and you will get a little better mileage with the cruise off on hilly roads. With the modern E-Throttle type engine control module (the cruise control is built into the ECU with E-Throttle and is not a separate unit anymore) they work together with the transmission control module and the shifting calculations are controlled based upon trying to keep the actual MPH as close to the speed set point as possible thus causing the higher/changing RPMs..

 

[Silver350]

On the 4 speed, the difference between 3rd & 4th is 740 RPM. (1:1 vs 1:.71). If the RPM change was less than this, I would think it was the Torque Converter unlocking to keep the engine at an RPM were it can provide enough power.

 

[vlamgat-SMB]

This thread hits at my pet peeve regarding the CC. Its gain is set to maintain speed no matter what number of shifts it takes and the overall driving experience is quite tiring. Would'nt it be nice if some techie out there could rewrite our control modules so we could allow the throttle applications to be much slower in order to avoid the shift hunting.

 

[regist1]

Re-gearing my differential has improved this greatly. Even in the Ozarks Hills my cruize works well at holding speed with minimal downshifts.

 

[vlamgat-SMB]

What do you mean by re-gearing? Did you change the diff; swap out some of the cogs; where did you source the parts?

Do you tow?

 

[regist1]

Changed the gears in the rear differential. I pull my 4000lbs Jeep on a 1500lbs trailer, the 5.4L does a good job with that weight. I am 2wd, but have a full conversion inside the EB van.

 

[vlamgat-SMB]

What gears did you use? And what was you final drive as a result?

 

[regist1]

I went from 3.73 with 245/75R16 to 4.1265/75R16 which made the effective ratio at the ground slightly lower then stock gears with the smaller tires. The speedo read about 5% off before I had it corrected.