Some may have seen this on my facebook name. Out of nowhere today, the car started to idle rough. Some key points:

- It never stalled.
- Drives perfectly smoothly as long as you are moving.
- Only occurs when you are slowing down and you shift to neutral to allow the RPM's to fall.
- It makes no difference whether the clutch is pushed in or not while in neutral (hence it's not a malfunctioning neutral sensor)

The observation:
As the RPM's fall, it dips below the idle RPM (between 750 - 900 rpm) as if it's trying to stall, and then it starts to idle hunt for 3 - 4 seconds before finally, the PCM automatically gives it gas to go to about 1200 rpm, stays there for 2 seconds, and then falls smoothly back to idle. While it's idle hunting, you can hear some hesitation and surging on the throttle.

Ambient temperature - 7 C. No precipitation. Roads are wet, from the salting of yesterday's snowstorm.

Theory:

1) It first happened after my fuel light came on for low fuel. I thought perhaps maybe the fuel lines got slushy so I filled it up. Still happening.

2) Coils/plugs came to mind, but I had these changed by the dealership in December 2007, and I know these last more than 22,000km that I have put on these coils/plugs; so this can't be it.

3) Clogged CAT, maybe clogging... but again this was also replaced for free by the dealership around February 2008 when I initially had my MS CAI issue at the dealership.

I decided the quickest thing I could do was, inspect for vacuum leaks, cracked/loose hoses or any sign of oil blowback into the intake area. No oil blowback.

Then, this thought came to mind, and was the only possible explanation I could come up with... dirty MAF sensor again! How? aggressive driving, high RPM's at highway speeds, in snow, or in presence of slush, backwash, essentially anytime after a snowstorm when the roads are salted/wet and cars are spraying it all over the front of your car at 100kph when you follow them.

I touched my CAI rainshield, it was kinda damp which is normal. I wiped that dry anyways with microfibre. poked my fingers behind the rainshield to touch the actual dry flow filter. That is also kinda damp too... couldn't dry that one really...

Found a 9/64" allen key at work and took the MAF sensor off. Also found some electrical contact cleaner (not CRC MAF). The MAF looked kinda dirty, with salt marks and some sort of green salt trail forming near the "bulbous" looking thing that hangs (I heard this is the temperature sensor, since the 2 resistive wires inside are the actual mass-air-flow sensor wires). Spray cleaned it. Stuck a microfibre cloth AGAIN inside the MAF hole, felt kinda damp inside along the walls too! Dried everything up. Inspected the two screens inside with a bent mirror (kinda like the one Dentists use). Everything checked out okay.

Proceeded to perform the NVRAM and KAM reset on the ECU (odometer TEST and brake pedal depress respectively). I think maybe the fuel maps for +20 C temperatures would be different for fuel maps when its -20 C outside. I think resetting it will help it re-learn the fuel-air ratio at these temperatures with more dense oxygen (Just a theory, I dunno about this one).

Started the car, and let it sort itself out. It did it's idle hunt thing for a bit, and then I drove it around to lunch and it seemed okay, but not perfect. I parked the car after lunch. Came back after work, started it, and everything was okay. No more RPM hunting at idle. It just falls to 1000 RPM, stops and then slowly does gown to 800 rpm or so as usual...

Problem appears fixed now. Will be on monitor for the next few days. The ECU probably still does not have sufficient data for it's fuel maps. I have not redlined it since the reset.

 

It's 3C today in Toronto. I cleaned the MAF again just to make sure.. Scrapped off this caked on green powder that was developing on the IAT sensor portion of the MAF sensor (the metal portion of the bulb sensor).

I don't know what this powder is..looks like salt corrosion.

Everything is now idling smoothly. The warmer temperatures also reduced a lot of rattling/odd noises too...

 

I have experienced this also...

"As the RPM's fall, it dips below the idle RPM (between 750 - 900 rpm) as if it's trying to stall, and then it starts to idle hunt for 3 - 4 seconds before finally, the PCM automatically gives it gas to go to about 1200 rpm, stays there for 2 seconds, and then falls smoothly back to idle. While it's idle hunting, you can hear some hesitation and surging on the throttle. "

Only when it is cold though... Today I had no problems with it and it is bearly noticable on my car.

 

I've been noticing it myself recently. My idle is set to 900 rpm, so when it stumbles, it's only down to 850. So it's not as bad as it would be if I had a 750 idle. But it's just enough to be noticeable. No ill effects. I'm thinking about slapping the OEM intake on and seeing if it goes away.

 

My MS CAI has not helped me one bit.

I've had massive issues with it.

I was told on here a while back to check the screens, etc.. Not long ago, I was driving to go to my brothers birthday dinner and the car freaking died on me, I had to leave it overnight about 30 minutes from my house because I had no 8mm with me.. I've tried messing around with the screens a ton, one out, none in, both in, etc. It will only idle at all if I have both screens in. What had happened when it died on me and I went there the next day to fix it, one of the screens was on a complete 90 degree angle to the screen nearest the MAF sensor. I straightened it up and had no issues driving home. Got home removed MS CAI and put in the stock one.

Not a problem since.

Ofcourse, now I need to tighten my belts because they're squeaking a bit... But I don't have the proper tools to do it. Could that make the idle abit gruff? Still having minor idle discrepancies..

 

the maf sensor is a wondrous thing. my turbo CAI intake setup was flawless, but the new owner of it is having a bit of stumbling at idle using it. I don't know what else to say besides make random adjustments or revert to stock and see if the issues go away. Trial and error to see what works for you.

 

You only had one screen in your turbo MAF tube, correct?

 

To adjust or remove the belts, you need a 10mm, 12mm and some large size that I forget off the top of my head. Just normal hand tools.. anyway, unless they're way over tightened, I don't see why they would hamper your idle.

 

I had a rat chew a hole through the CAI filter and it needs to be replace! Sucks!!

 

I had NONE in my turbo CAI. It worked well that way too. The piping and couplers had gradual curves and nothing abrupt.

 

When you sold the car, did it have the ceramic coated AEM CAI, or was that with your turbo setup?

What I actually wanted to ask was: What intake setup did the guy who purchased your car have?

 

my car isn't sold

I don't need the cash, so I'm not overly worried about offloading the vehicle.

 

That's what you get for living in a place with -30 degree winters Haha! Get over here to BC, it's nice and mild! I've never seen a rat in my life, they don't need to migrate indoors during the winter to survive.

 

"The new owner is having a stumbling idle"

Dyuhh, confused me

Is his car N/A?

 

Haha, yeah, but try to get in there with the stock intake in... I guess I could remove it, but it's just such a PITA to squeeze it back on.. That, and theres a pile of snow ontop of my car right now. Should've parked her in the garage, it would be something to do today.

 

ah, new owner of the turbo cai he's... turbocharged

 

Ahh okay, then I have no clue..

Was gonna say, if he was using a MAF tube without screens and N/A, that could be the problem right there. I know my car won't idle without them.

 

LMAO... It happened in the summer time. My garage is outdoors not indoors...lol I'm a country girl now... City folks don't know what rats are...

I've been to BC...it's beautiful there...

 

D'oh outdoor garages! Funny how a rat would get in there to do that, though.. :P

Check out a pic of the 8 by my lakeside <3 BC..





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WoW~~~ So beautiful... Yeah wish I was there right now...

 

you have to watch the dry flo filter very carefully... and try to clean that rainshield sock and keep it dry.
The MAF also needs to be cleaned more often as proper maintenance if you have been in a place like what Toronto has gone through this winter so far... it's all that fine mist of SALT/DIRT that goes through everything and eventually lands on your MAF sensor and IAT sensor. As we all know, salt conducts electricity,and ***** up the readings.

With the winter we're having now, I would clean my MAF sensor again at the end of March just to be sure.... it's quick and easy. For me, it is a 9/64" allen key.

 

How do I do that? Is it easy?? Maybe you can show me?

 

There are DIY's on this forum, it's very easy. Just 2 screws to remove. The MAF sensor pops out, and you spray 10 - 15 blasts of genuine CRC MAF cleaner (available at Napa Auto parts).

If there is no Napa auto parts near your place, other people have used electrical contact cleaner and/or Brake cleaner. But I use the real stuff that's made for it...

 

lol.. they're all too scared to be hangin' out in Surrey.. that's why

 

Are you sure it wasn't one of your minature Yorkies?

I hear they like to chew on everything.