I've noticed that when I begin to slow or approach a stop in 3rd or 2d gear and do not downshift, obviously giving the engine no gas, and engine-braking, all of a sudden I feel the deceleration curve plateau out and the car takes on more of a "coasting" feel -- feels as if the clutch semi-releases or the transmission moves into a lower gear or neutral (but not quite). I am not complaining here, it seems to be an intentional feature, but one I was unaware of, and not mentioned in the documentation. I may be betraying ignorance or age here, as I am returning to a manual transmission regularly after 15 yrs. of automatics, but is this on purpose? If so is it a feature unique to this car or has it become standard on manual trannys? Is it a function of the synchro, or some other part of the gearing, that senses a change in engine-road speed ratio, and "loosens" the engagement to avoid a stalling?

 

That would be the case in any manual transmission car. As your RPM's decrease towards idle speed, engine braking is reduced, and once you're at idle speed there is essentially no braking resulting in the coasting feeling.

 

Very well put

Another thing to consider is modern electronics and deceleration in manual transmission... When you decel in a modern car the PCM shuts of fuel flow to the injectors becuase it is wasted fuel. A slight difference between todays cars and cars from 15 years ago... but worth mentioning...

 

Jamikest at times when I stop at a light the idle in my car drops to where the car acts like its going to stall its a autostick and the dealer says that they can't duplacate the problem it does it about once or twice everytime I drive the car any guesses?

 

Mine has done the same thing maybe 2 or 3 times, since I had the oil changed about 2 weeks ago. When you pull to a stop the idel drops very low and if it hasn't recovered and you attempt to excellerate... Nothing.... A huge "flat spot" then it will recover (after maybe 2 - 5 seconds) and it acts normally again. It's like no fuel is being sent to the injectors.

 

Does the engine actually not have any power when you press the accelerator at this point?

An engine idle that changes can come from various reasons. The AC coming on, a large electrical load coming on, etc. can all cause the idle to dip. Also, in OBD2 systems, the vehicle runs several monitors which can force the purge system, egr system, etc. to run a self test which also may be noticeable to the driver. These would all be normal, and may not be reproducable by a dealer. The dealer would also have no way of diagnosing this as the items I described would be normal.

Is this what is happening in this case? I don't know. I could only answer that by driving it.

 

when i stop at a light ext. the car acts like it wants to stall runs really ruff then it catches itself I to have noticed this after a oil change is there a possible reset or something next to the oil filter that could have been jared loose

 

no power at at all when this happens I did not have the AC on either it happens day or night cold or warm no ryme or reason

 

No A/C on when it's happened to me either.

 

Hmmm Check the oil filler cap and make sure it is secure... A loose oil cap can allow additional air to circulate through the pcv system and cause a rough idle. This is only prevalent on MAF vehicles... and I have not tried this on a CF yet to see if it is sensitive to this.

Again, without having driven your vehicles, I am just guessing..

If the problem is bothersome enough, and the loose oil cap idea does not pan out, a trip in to your shop may be in order. If any TSB or service info comes out I will post for you. Next time my district rep is in the area (usually every week or two) I will ask if she has any knowledge of a rough idle condition in CFs.

 

Hmmm... curious to have two reports of similar problems following the first oil change....

 

The condition happens too rarely for now to bring it in. The likelyhood of being able to duplicate it is pretty remote. It's one of those "Drive it and Watch it" things.

I will check the oil cap.

 

Mine is in the shop now has been since Monday but they say that they can't duplacate the problem this is the second time I have brought it in and still nothing resolved is it unreasonable for me to refuse to take the car back untill its fixed? What should I do? I can't trust that the car won't leave me stranded somewhere and there is no pleasure in driving it this way and i'm afraid that I will cause permanant damage

 

I would set up a date with the service manager for Saturday morning. Take a long, leisurely drive around Tucson until the problem rears itself. I know from experience you'll have plenty of chances to stop at lights and duplicate the problem.

My professional Five Star diagnosis is that the Steve ChristyClowns are blowing you off. Don't take it personally, it happens to everybody eventually.

 

Did anyone ever get this issue resolved? This has happened 4 times to me now, 3 times it stalled. The fourth time i had the car in 'N' as a precaution to stalling, well it dipped down, nearly stalled then proceeded to hit 2500 rpms without me touching the pedal. It doesn't bother me too much but it is annoying. If no one has managed to solve it, maybe we can list what Extras you have to see if a common element could be causing the issue. I have a Speedtuning chip and K&N air filter. I'm thinking maybe i need to clean the filter as the issue has progressively got worse and it was about 6 months from being chipped and filtered to the first instance. Any ideas?

 

...I would attribute some (but certainly not all) of the above strange behavior to engine management. For one, I heard the ECU intervenes when trying to launch the car from higher rpm. I have also heard that it will intervene if you get close to the 6,000rpm redline, and will cut spark and fuel abruptly. So, there is some "babysitting" going on, to make sure you don't cross any boundaries. On a modern car, it is easy for the ECU to manipulate spark and fuel curves depending on engine operating parameters. Knock will retard spark significantly. In other cases, it will lean the car out or richen it up for emissions or performance reasons. Sometimes, modern ECUs will manipulate what the engine is doing for NVH or refinement reasons. Making it transparent to you is the tricky part.

With drive by wire throttle, the same can be said of throttle opening (regardless of how much your foot is to the floor, it could end up doing something else. See how far you can rev the engine with an abrupt stab to the accelerator, and watch what happens. If it hits a ceiling of sorts, it may have drive-by-wire. You can also remove the shroud and look at the TB, see if there is a steel cable or electrical wiring coming off the thing). In the two weeks that I have owned the car, I have not removed the shroud from the engine yet to have a look, but I would assume that the throttle is drive by wire, and thus manipulated at some point by the ECU.

For those of you that have a car that stalled, check for a MIL and retrieve the code. OBDII codes are standardized, so if you post it here or do a google search, you ought to be able to find out what the source of the problem is easily. There are so many sensors that could affect engine behavior (TPS, cam and crank, mass air, etc) that without that shred of information, understanding why the engine is behaving that way could really be a wild goose chase.

 

this was happening to my wife's bmw X5. the culprit was excess oil from the K&N was clogging/malfunctioning the mass air flow sensor. i removed the K&N...had them replace the MAS...and have never had the problem occur since.

i must of over oiled the K&N after cleaning it. less is better.