gserep1

Gentlemen,
I just installed a new K&N air filter on my 99 GS4, and so far, I have noticed no ill effects. I DID clean the throttle body AND the MAF before putting the filter in. The idle has always been around 500 rpm in drive with the A/C and lights off and the engine warm.

Strangely enough, just by shifting into reverse, the idle raises 100 rpm every time. It is really eerie, and based on that, I too subscribe to the theory that it is a software programming glitch.

It should not matter to the MAF, throttle body, or TPS if the car is in forward or reverse.gear...How would these parts know? I definitely get a 100 rpm difference. Give it a try and see if yours does the same, or if I have a wierd car.

It has never stalled, but it has gotten pretty close to 400 rpm as indicated on the tach. I have a new AUTOEXRAY Scanner that says that it is between 458 to 515 rpm at the slowest, so the stock tach is off a bit. I don't believe that you should HAVE to run the A/C system just to get a smooth idle. However, It is definitely smoother if the A/C is engaged, or lights are on. The other thing is...it doesn't seem to matter if it is just the parking lights, or all the headlights are on... The engine speed raises up the same amount.

This leads me to believe that the computer is programmed to raise engine speed if there is any additional current draw on the alternator. Lights or A/C will do the trick. My idle also raises if the cooling fans come on..(like in a drive-through at Mc Donalds, or at the ATM. My idle goes up. (Of course this is with all accessories off) The scanner shows that the fans come on at 208 degrees and turn off at 192 degrees. I have driven with it attached, and no faults are indicated.

I believe that when either the a/c is on, or the lights are on, the computer sees the request, and it then sends a signal to the Idle Speed Motor to allow more air to bypass the throttle plate, and flow more air to the engine, and thus raise the idle. The scanner also shows that the computer knows when the lights are on or off, as well as when the A/c is on or off, and if the car is in gear or not. I am still lost however as to why I have one speed in drive, and another in reverse.

I will be watching for the oil contamination of the MAF. I have used K&N air filters on every car I owned since 1986, and once I learned how to properly clean and oil the filter, I never get the "greasy maf" syndrome you describe. Just clean it, and don't over-oil it.. Be sure to use the K&N red oil SPARINGLY over the pleats, and nothing else. Also let the oil settle into the filter pleats for a minimum of 30 minutes after oiling. I put mine in the sun after oiling, and the oil spreads out over the pleats. After 30 minutes, I put my filter back in. I used to over-oil the filters all the time, and it resulted in greasy throttle bodies. This is explained in the cleaning instructions, and should not be overlooked.

Keep in touch,

GSEREP1

whitels

Here's a theory about the idle rising 100 rpm in reverse. It may have to do with the intake air hose leaking. The air leak could be from a loose clamp or a little serration along the length of the air hose.

When the car is idling in neutral and then you put it on D with your foot on the brake, the engine tilts one way by a small amount and compresses any hole and seal the leak. When you put it in R, the engine then tilts the other way, stretches the hose slightly, and opens up the hole creating an air leak. This leak causes the idle to rise.

What to do: remove your air hose, insert a flashlight inside while you're in a dark room, and probe for an opening.

bitkahuna

iTrader: (20)

I tried that with a girl once.

whitels

LOL

I forgot to add, when it's too dry, it helps to put a drop of Mobil 1 5w-30 on your finger...much like you would do when applying oil on a new oil filter gasket.

gserep1

TO: WHITELS,
Thanks for the info, and I will definitely check into it. However, I don't believe that I HAVE an air leak.
I now have 86,000 miles on my GS4 and it has NEVER stalled while in drive (or any other gear). The engine really runs smooth at all times. However, 485 to 515 rpm in drive is in my opinion a bit low. Turning on my headlight switch just one notch to the parking lights will give me 600 plus rpm, which smooths out the car even more. I get a little vibration at low idle speed. This is not a miss, but simply the engine is turning too slow to handle the load of the transmission against the brakes. Just a bit more air into the throttle body cures it.

I don't believe that the air hose is leaking because the engine moves very little when shifting between gears....( I have checked. because I leave the hood open sometimes to check for broken motor mounts.)

Just to satisfy my curiousity though, I took off the air intake hose, and checked every inch of it, and as I suspected, it was fine. The only time I had a real rough idle was just after I bought the car. (I did what BITKAHUNA suggested could have happened) and as a trial, I put some cheap 89 octane gas in the tank. That one incident was proof enough that low octane gas in this car is NOT acceptable. It took a whole tank of good gas to get my smooth idle back, and I have not used the cheap stuff again. I am picky as to where I get my gas, and 87 octane is out of the question. Poor gas quality will give you a bad idle..even if it is 91 octane... I am a witness.

At my 90000 mile service, I will finally change these original spark plugs and do the timing belt, water pump, thermostat, support bearings, and tensioner. I hope it will run even better, but don't expect it to run a whole lot better, as it is very good now.

The other thing about the air leak theory is: IF there was a leak big enough to affect the idle, it would have to be after the MAF and before the throttle plate. A reduction in air flow across the MAF will cause it to send a "lean condition " signal to the computer, which would in turn cause the "check engine" light to come on. Run your engine without the air hose connected to the throttle body, and you will get a check engine light right away because no air is going across the MAF.

When I was talking about more air getting to the engine in my last post, I was referring to the increase in air that occurs when the Idle Speed Motor , or CONTROL within the throttle body opens. It is totally responsible for the engine idle at all times. When the engine is cold, the idle speed motor opens wide, allowing extra air into the intake, because the injectors are programed to flow more fuel to keep the cold engine running...(mine is about 1800 rpm when cold by the way.) As the engine warms up, the computer signals the Idle Speed Control to close off some of the air in the throttle body, and lower the engine speed. All of this occurs automatically, without pressing the accelerator and moving the throttle plate manually.

I still think that the Idle speed Control is sending more air to my engine in reverse than in drive, and that is why the idle is different.

I hope I don't come off sounding like a pompous know-it-all, but it just my belief. I am always open to another opinion, and I will check it out. Now the question is....am I the only one who has a car that has a faster idle speed in reverse than drive, or do others experience the same thing?

Keep in touch, and thanks for the food for thought!
GSEREP1

FutureGS400

I don't personally have an idle problem of any kind-of course my car only has 4,700 miles on it
It is so quiet and smooth that you have to check the tach to make sure the engine is even running (at idle of course!) Not so much now with the RMM exhaust though Appreciate all the advice here just in case it starts to happen later...

gserep1- an idea occured to me regarding the difference in idle speed from drive to reverse. Someone referred to the idle speed being different just with lights on; could it be that the reverse lights coming on are having an effect on your idle speed?

gserep1

Hey FUTUREGS400,
I hope you meant 47 THOUSAND miles. If you have 47 HUNDRED miles, you truly have a low mile 2000 GS. Either way, that is one sharp car you have!
GSEREP1

FutureGS400

Nope, it is a little over four thousand and seven hundred (4,700) miles! When I bought it , it had less than 1,000 miles on it. Long story, but basically it was a new car that happens to be almost 4 years old! Yes, I got very lucky!

elclassico

i have a K&N filter, never oiled it, but never had a ruff idle before i installed the filter. thanx!

DASHOCKER

iTrader: (2)

Does it idle above 3 in park or in drive?

whitels

It idles at 4 at the lowest when it was bad. It's been fixed and I'm at 5+ or 6 (with lights on).