Questions - cold idle and break noises
 

I have two questions about my 2007 FEH. I could not find answers in the FAQ section, so I thought someone might be able to help. My cold idle starts quite high, like 1500 rpm, then drops to ~1000 rpm when warm. Does that sound right? I don’t really like the high idle but I figured it might be charging the HV batteries.

I know it is normal to hear the breaks pressurize/depressurize when the doors are opened. I however, with no know input from me, have heard it happen twice, all by itself. I picked up the vehicle in September. I thought I could check if others had similar experiences?



Thank you

Re: Questions - cold idle and break noises
 

The first one sounds failry nomal. I think the idle speed seems to depend on the temperature of the engine and the charge of the battery.

I *think* I've heard my brake sounds sometimes a few minutes AFTER exiting the vehicle and such....

Re: Questions - cold idle and break noises
 

Both are normal.

The brakes also "depressureize" about 5 minutes after coming to a stop and removing the key. You should hear this EVERY time... if you hang around the car for a few minutes after.

-John

Re: Questions - cold idle and break noises
 

My '02 Explorer also had the " Cold Idle" speed at about 1800 rpm. I believe this to be normal and part of the overall design. Probably to prevent it from stalling out when cold. On the Explorer it would hit the gas a bit while in park and this would reset the automatic choke and the rpm's would return to normal 600 rpm.

Re: Questions - cold idle and break noises
 

I believe it's something like 3 minutes after key off that the brakes depressurize. They're pressurize if the vehicle hasn't just been driven moments before and you unlock or open a door. Absolutely normal and documented to some degree in the owner's manual, and to greater degree in the factory shop manuals some of us purchased elsewhere (eBay, etc.)

I can't recall my idle at startup... I paid attention to that for awhile but ignore it except for driving (to always keep it below 2k RPM if at all possible.) The idle speeds will feel foreign for awhile, but it too is normal for a CVT (Continuously Variable Transmission) vehicle like the FEH.

Re: Questions - cold idle and break noises
 

A reason for the high idle at cold start in lower ambient temperatures could be to prepare the climate control system to heat the cabin or defrost the windshield. Remember that the Atkinson engine cycle is more efficient than the Otto cycle; therefore, less of the energy from the fuel is being lost as waste heat. You can increase the heat going into the coolant by reducing the efficiancy of the engine via retarding the spark; and you can increase the amount of heat being generate by raising the power output of the engine by increasing its speed.

Re: Questions - cold idle and break noises
 

Hi All.

I appreciate your comments. I guess I will just learn to live with the high cold idle. As for the pressurize/depressurize of the break system, the two odd times it happened, the car had not been used in about 24 hours. It just seems strange.

Thank you :-)

Re: Questions - cold idle and break noises
 

teichra - buyhevs is correct. When you say "strange"...you mean
"strange" in relation to every Otto-cycle vehicle you have owned in the past. The FEH's Atkinson-cycle (IC) engine has its specific power curve that is compensated by the electric motors at times chosen by the PCM computer in this truck. It takes awhile to get used to the times you hear high revs from the ICE but do not "feel" the torque associated with Otto-cycle engines. After a few months of driving I learned to anticipate the boost from the EV motors......

Even at idle ....I believe that sense of "higher than necessary" revs is partly due to the design differences in the Atkinson cycle engine.:D

Re: Questions - cold idle and break noises
 

The past few days, Colorado has been colder than Alaska.

Last night was -17'F at my home. The night before was -20'F.
Steamboast Springs, CO was -35'F the same night.

At these cold temps, my idle when "coasting" is about 1350.
At this extreeme cold, my idle when in "park" at a drive-thru was 1700 rpm.... even 10 minutes after start-up. Yes... sounds and feels wierd.

It may just be so simple that it is trying to keep the car ( and cabin ) warm.

Since the FEH must be at 1000 RPM to enter EV mode, you can see this is out of the question, no matter the state of the battery.

The good news is.... I got to go into EV at +4'F a few days ago!
;)-John

Re: Questions - cold idle and break noises
 

The brake system pressurization happens not upon door opening, but upon door unlocking. Maybe the keyfob was pressed? Or maybe the '07 even has some new proximity sensor that will do this when the keyfob comes close to the vehicle?