This is the second time that im at a redlight and then after being there for about 2 minutes the a/c backs off for a second and then goes back to normal. What the heck could that be?

My car when in idle sometimes shakes a little as if it were missing and then i took it to have diagnosed even though there is no check engine light and they did not find anything at all.

Any ideas, opinions or suggestions welcome.

Thanks!

 

You mean the interior fan slows down and then speeds back up?
That happens on one of my cars when the high speed engine fan kicks on.

On my car I also had a low idle condition that I corrected with tuning.

If your car shakes it could be a dirty throttle body and idle air control, or just needs a tune up. Could also be a bad engine mount.

I'm thinking it needs a tune up if it slows down when the fans come on, sounds like power at idle speed might be low, idle speed control (IAC) dirty, etc.

 

So far ive done plugs and wires and new Air filter. Ive yet to check the throttle body so i will but as for the IAC how do i check that? (sorry im new to some of this stuff)

My idle is at 500...is that considered low?

Thanks alot for the help!!

 

Sorry for asking again i just got your answer in the other thread. I really appreciate the help though!

so since my idle is low im going to check the throttle body like you said i just dont know how to check the IAC.

 

Be careful with the IAC, take it out of the TB but only clean the tip of it. I've heard you can ruin them by getting cleaner down inside, but I never had that happen.
Clean the TB real good. If it's real dirty around the IAC passages that could be the problem.

You might actually have dirty, leaking injectors or something causing unburned fuel to get to the O2 sensors, maybe even a fouled plug or bad wire. I got this info doing a search trying to find out why my car was idling so low.
You might even take out a rear O2 and see if it's black, if it is you have excessive unburned fuel going out the exhaust.

 

I appreciate your help. I will definatly check into all of that.

 

No problem, hope you find an easy fix for it.

 

Alright here is my update:

When i looked at my ThrottleBody it was dirty as hell! so i went and bought Sea Foam Deep Creep and MAF sensor cleaner. I removed the TB by following instructions of InstallUniversity.com. When i went to go loosen the clamp around the TB that holds the black rubber accordian thing that is connected to the MAF, it was really loose the previous owner must have not tightened it.i then Removed the 2 coolant tubes that go to the tb and the air tube and finally got the TB out of there. That thing was gross and the back is worse i cleaned everything i could and it ended up very clean but the back no matter how much i scrubbed witht he toothbrush and cloth it wouldnt get any cleaner than this: (thats the back after i cleaned it the front is very shiny although did not take a pic of that)


Then i removed the IAC and it was dirty as well along with the passages inside the TB that lead to it:


I cleaned the IAC with MAF cleaner cause i was told at the auto store it was safe for all sensors. I was not able to keep the liquid from actually going into the sensor like you said not to but never the less i cleaned it and most of the passage that leads to it in the TB.

The SCARY part:

When i hooked up everything and i double checked everything a few times to make sure there was none of my tools in the engine compartment, cloths anything loose...etc. I then turn on the car and it starts making all kinds of noises. Loud clanking and a sound that sounded like alot of air or a huge vacuum in my engine like a black hole or something. It was crazy, i was beside myself i thought i screwed up my car. In a panick i turn off my car and look around but see nothing!.....but then i turned it on again and everything was fine. Didnt hear anything like that again. No SES light....nothing.
I wonder if thats normal after cleaning the TB? maybe too much Seafoam? it was still a little moist. but i thought the engine swallowed a frog LOL...it sounded really bad.

Verdict:
The only thing i got out of the whole experience was a quicker response from my car when driving it. The idle is still at 500 when im at a redlight. Oddly enough though when i put it in park and i finally got to my house it was a little above 500 and it was doing a little better. But the real test will be tomorrow when i do my usual driving ill tell you more then.
So if you have anythoughts on what those noises could have been please let me know!

 

The noise probably was from a good amount of seafoam in the intake and the IAC resetting itself.
I hope it relearns, I know I found my own TB clamp loose once, it was acting a bit strange.
If it was getting any air through the loose clamp it would be unmetered by the MAF and would learn that over time, when you correct that problem it may have to relearn since it's metering all the air now.
Hope it works out for you.

 

Reset the computer in your car by pulling out the fuse and leaving the key in the Acces. position. As far as the noise it could have been the IAC getting the fluid in it. What did the RPM's do when it was making noise was it surging or steady? Resetting the comp will force the car to relearn the idle (forwarning it may sound like crap for a few minutes) and also the rest of parameters while driving. How many miles are on it? May be time for new O2's.

 

Well after driving it today its still the same. It improved on response while driving but thats pretty much it. It still boggles down at idle and the ac still backs off for a second when it happens.

Which fuse do i pull? and when you say access you mean having key turned to the point before actually turning the car on?
I didnt check the RPMs when that happened because i panicked and tried to get out to see if i saw something fall into the engine bay or something then turned off the car as soon as i could....LOL yes i panicked.
It has 68,000 miles on it. I havent checked the o2's yet but i will.
Ive never done that though is there anything specific that i should know about taking out the o2's?


Thanks in advance!

 

You can take all O2 sensors out of these cars with a 7/8 wrench, you don't need a special socket or anything.

 

Thanks!...ill keep you posted.

 

From the install university site:

http://www.installuniversity.com/ins...sity/index.htm

1. Turn key to the "on" position but don't start car
2. Pull the PCM BAT and PCM IGN fuses in engine compartment
3. Wait approximately 5 minutes
4. Turn ignition off
5. Replace fuses

Remember though that it completely resets the computer so it will relearn everything and the engine may seem like it is running like crap but its normal for a few drives then it should be good and you can see if it helped or not. The accessory position for the key is so the radio comes on but the car is not started (one click before turning the car over)

 

Also did you clean the MAF when you did all the other stuff? And what plugs and wires did you go with? I put in shitty champion plugs and have a misfire under load that pisses me off. NGK's and MSD wires are comming soon to hopefully fix it. You may want to try seafoaming the bastard and see if that helps at all.

 

I put NGK tr 55's and MSD wires in it when i did the change. I had also Seafoamed it before the i did the spark plug change. although only a little smoke came out hardly anything at all i guess it was pretty clean. i did not clean the MAF infact i only glanced at it and saw that there was nothing blocking the screen. I should probably double check it and clean it.

The Update:
My car was still doing the little rough idle along with the A/c thing the day after but has since then gotten better.i think it has relearned everything like you guys said. It still idles at 500 but so far has not done the a/c thing or rough idle. The a/c isnt as cold as it was when i first got it but i think that has to do with the recent heat we've been getting here in Miami lately. My car had a problem where i couldnt turn it on with out priming the fuel pump atleast 2 or 3 times and i got used it. Now it turns on just fine without the first turn of the keyt i didnt know that a dirty IAC or throttle body would have such an effect on the car turning on.

Anyway i will keep you guys posted if anything else happens but i want to thank you guys who helped me on this thread. Thanks for your info on everything my car is running better thanks to your help.
As you can plainly see...i cant thank you enough LOL

 

Buy a can of MAF cleaner ($5) anyway and spray the **** out of the maf wires and screen, never hurts. Let it air dry for a 1/2 hour then reassemble.

 

Who said 500 rpm idle is low? Do you have an M6? I read that for an A4 it should be about 450-500 in drive with the brake on and about 500-550 in park. That what my car runs at and it runs fine.

 

I don't know if I said it but I've been dealing with a low idle problem on my car.
Stock idle is programmed at 550 rpm at operating temp with ac on and 650 with ac off.