Took my M45 Sport for my first long trip. About 1,300 miles down to So California. I noticed that when going downhill with the cruise control engaged (regular mode or radar mode) the car will surge intermittently, at regular intervals, every few seconds or so. Gas on, gas off, gas on...etc. It's really annoying. This is the first car that I've owned that does this. Cruise works perfectly in every other way, only when going downhill does it do this.

Anyone else have this problem?

Tony

Tony407 wrote:Took my M45 Sport for my first long trip. About 1,300 miles down to So California. I noticed that when going downhill with the cruise control engaged (regular mode or radar mode) the car will surge intermittently, at regular intervals, every few seconds or so. Gas on, gas off, gas on...etc. It's really annoying. This is the first car that I've owned that does this. Cruise works perfectly in every other way, only when going downhill does it do this.

Anyone else have this problem?

Although not a nice feeling, I am not totally surprised by this per se - I have seen it on other cars. Both up and down hill, although gentle downhill slopes trigger the symptom more than anything else - up hill tends to depend on the steepness, the power of the car, etc. You can get downshifts as the car tries to keep the velocity. I simply turn the cruise control off in such situations.

Frankly, all control systems can develop oscillations, if the input is at the right frequency or amplitude - as long as it is not underdamped (i.e, the oscillation does not grow), then the oscillations will not grow in magnitude. If the design of the control system does not damp these out (by slowing down the feedback as needed, etc.), then you get these small oscillations. A trade-off between better speed control on level ground and hills, basically.

Depending on the particular slope involved (apparently your car slows down on these slopes with no gas), this leads to the symptoms you describe. I don't know if there is a particular solution for your situation, but I doubt it.

Near my house for example, there is a fairly steep downhill section (on Silver Creek Valley Road off of 101), where I tried to see what would happen with the cruise control on my older 2003 M45. When the car let off the gas, it merely kept accelerating slowly anyway since the slope was steep enough. So, I did not see oscillations.

BTW, does this happen on all downhill slopes, or on just a particular one? That is perhaps an indicator of sort whether you should have the car checked out - just in case. If on all downhill slopes, then have the dealer look at it and test the cruise control circuitry.

Z

there is a recall for the new M's cruise control... just to let you know

infinititech1 wrote:there is a recall for the new M's cruise control... just to let you know

Ah! Even better information than I can provide!

Thanks,

Z

infinititech1 wrote:there is a recall for the new M's cruise control... just to let you know

Hmmm...I thought the recall only pertained to the radar cc. I'll have to look into that some more. Thanks.

Tony

yours doesn't have the radar?? hmm...i know it fixed some issues with cruise control messing up... but i think it had to do with the radar

infinititech1 wrote:yours doesn't have the radar?? hmm...i know it fixed some issues with cruise control messing up... but i think it had to do with the radar

Yes, but unless I'm mistaken, I wasn't using the radar cc when this happened...jut the coventional cc. I'll have to double check that as well too.

Tony

The pulses happen whether I'm using conventional CC or Intelligent CC. Here's a video of my tachometer while it's pulsing:

http://s143.photobucket.com/al...1.flv

Tony

No one's watched it? Or no one cares? LOL

Tony

are you sure thats not gear hunting in the tranny? it at 2000rpm, that seems kinda slow to me, ie, you must have set it at a low speed, and it could be looking for the right gear, I've seen this before, I think at the 70-80km/h range (not sure on MPH)

Does it do it all speeds? ie, some of the higher speeds like over 60MPH (100km/h)?

tk

tkeskic wrote:are you sure thats not gear hunting in the tranny? it at 2000rpm, that seems kinda slow to me, ie, you must have set it at a low speed, and it could be looking for the right gear, I've seen this before, I think at the 70-80km/h range (not sure on MPH)

Does it do it all speeds? ie, some of the higher speeds like over 60MPH (100km/h)?

tk

Gear hunting downhill? I've had few that gear hunted while going uphill, but every cruise control I've used while going downhill merely shuts off the gas and basically coasts. I've never had a car that's done this. Yes...it does it at all speeds. The video was taken while driving 60 mph I believe.

Tony

Tony407 wrote:No one's watched it? Or no one cares? LOL

I have to admit that this is weird.

Does not happen in my 2003 M45. As you said, it just coasts going downhill, and when the slope is steep enough, it just accelerates gently, unless I downshift to get some engine braking.

What is the grade of the downhill slope where you saw this effect?

Z

szhosain wrote:
What is the grade of the downhill slope where you saw this effect?

Z

Well, I was coming up and down some mountain passes, and pretty much on a windy highway with many ups and downs. It did it fairly consistenly with any slope steep enough that I could have put the car in neutral and let it coast down.

Tony

Tony407 wrote:Well, I was coming up and down some mountain passes, and pretty much on a windy highway with many ups and downs. It did it fairly consistenly with any slope steep enough that I could have put the car in neutral and let it coast down.

Very strange indeed ...

Have you any response on this from the dealer at all? Maybe the electronics in the cruise control need to be checked out/replaced.

Z

szhosain wrote:
Very strange indeed ...

Have you any response on this from the dealer at all? Maybe the electronics in the cruise control need to be checked out/replaced.

Z

No, not yet. I thought I'd start by finding out if anyone else here had a similar issue. Unfortunately, the closest Infiniti dealership is about a 3-hour drive. The dealership where I purchased the car is about a 4-hour drive. I guess that's my next step. I'll give them a call and see what they say.

Tony

I have the same problem...will have the dealer look at it next time take it in.

Bodhizapha wrote:I have the same problem...will have the dealer look at it next time take it in.

That sucks. Let me know what happens will you?

Tony

How do you use the regular cruise control? I was facing the sun while driving and I guess the radar cruise control started blinking and turned off. My car also has had the recall fixed.

Popsickle wrote:How do you use the regular cruise control? I was facing the sun while driving and I guess the radar cruise control started blinking and turned off. My car also has had the recall fixed.

When the CC is off, press and hold the CC button down for a few seconds. This enables regular CC.

Tony

Thanks Tony. I wouldve never figured that out lol