RPM RACING WITH CRUISE CONTROL ON

joey2cool · 10-13-2011, 01:05 PM

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 · 10-13-2011, 02:06 PM

Quote:

Originally Posted by 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?

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 · 10-13-2011, 02:23 PM

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 · 10-13-2011, 03:20 PM

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

joey2cool · 10-14-2011, 12:45 PM

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.

Many thanks for the fast responses!

Ford_6L_E350 · 10-14-2011, 02:34 PM

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 · 10-14-2011, 10:22 PM

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

Quote:

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 · 10-15-2011, 11:27 AM

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 · 10-17-2011, 12:54 PM

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 · 10-17-2011, 02:26 PM

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