Rough idle, strange shifting - MAF sensor?
 

Hey guys,

I'm having trouble where my car is idling very rough almost as if it is misfiring once it is heated up. Sometimes when I idle for a long time, my engine starts loping and chugging. I also have an issue where my trans goes in and out of lockup during light acceleration under load (hills, passing) when it is in 3rd or 4th gear. I found a GM TSB that points to the MAF sensor and I was wondering if anyone has ever heard of this?

I've replaced my plugs and wires in the last 1000 miles. Also, its worth noting that the engine runs smoothly when not idling and my fuel economy is still in the high 20's.

hmm tough...

so while driving on slight acceleration you have chugging?

I would think more along the lines of a throttle poSition sensor. They cause rough shifting and if it's worn out in certain spots it can cause your other issue because the computer is getting an incorrect voltage signal from it. The engine light doesn't need to be on for it to be bad

any dtcs? even if the light is not on.

Plug in a scanner. It might come up with P0100, P0101, P0102, P0103 or P0104, which all have to do with the maf. If the service engine light hasn't come on, the scanner may set the code, but will have "pd" at the end of the code, meaning pending, or the code hasn't been triggered enough to set the ses light yet.
Mine did the same thing one time. Try cleaning the maf, and if that doesn't work, get another maf.

No codes - hooked up my scanner and everything was clean

it only does the trans lockup/un-lockup thing when I'm in overdrive and press the accelerator to speed up. it does one of two things: A. shifts to 3rd to accelerate and converter locks/unlocks while accelerating or B. holds 4th but the convertor locks/unlocks while accelerating.

The rough, loping idle only happens after I've been idling for a long time such as being stopped in a drive through with the car in drive and foot on the brake for over 4-5 minutes.

also, when the car is heated up and you listen closely to the exhaust at the muffler it makes a sputtering-type noise that isn't consistent. kind of like the engine is coughing at random

Still may want to clean the maf. It couldn't hurt.
Any of the vacuum lines unhooked?

My moms Olds intrigue had 2 bad motor mounts and they caused a very annoying vibration/sound almost like miss firing and made it shift like it has 200k on the trans(only has 90k miles) check out all your mounts.

So, I know the MAF has some sort of coating on it that you dont want to disturb. What do I use/ how do I clean this thing?

I think this should be my first plan of action and I will also look for vacuum leaks too

Use mass air flow cleaner. Some sites will say use brake parts cleaner, but it's not for the maf.
There isn't really a coating per se, but when you have it apart, don't touch the wires or anything inside the maf.
The way I did mine was to wait for the car to be off for a minute, then I unplugged the maf. Next, I used a torx bit to take out the 4 little bolts holding it together. After it was apart, held the maf away from the car and sprayed the maf cleaner on the wires and rods in the middle until clean. Mine went from black to gray. You'll want to wait until the maf is completely dry before starting the car, but maf cleaner evaporates rather quickly, so it won't take long.
Installation is reverse of removal.
One other thing, make sure the arrow that shows flow direction is facing the same way on reinstall as on removal. The arrow direction is toward the plenum, just in case.

thank you for the info - I am planning to do it after work one day this week. Just found out my brakes are shot too, so buying some new pads and rotors too. I guess I can't complain though because I got 110,000 out of the stock rotors.

My stock rotors have 186500 and counting. They are starting to get a little thin though so itt is about time for a big brake swap.

MAF and outside temperatures
 

Well as I today do my 2 times a year reprogramming of the pcm, this sounds familiair.

My alero needs to be reprogrammed twice a year, once when outside temperatures drop below zero
and once when its spring and temps rise.

the car (alero 99 2.4) starts to shift rough (hard), idle becoms a bit strange, kickdown hesitates, and shifting starts to get only in the high rev counts
this happens twice a year and only when temps outside shift.

then i pull the battery cables a few minutes, connect again
start and idle until normal operating temp is reached, then 2 minutes at 1200rpm
and next a 5 mile drive and programming is complete

all strange behavior is gone then, nice idle, smooth shifting and kickdown as it should be.

Think it has to do with the MAF sensor and outside temps.
I have the car for about five years now, and this happens every year.
glad it can be solved in 10 mins, and bad it leaves the radio empty.

(got this reset procedure from my Haynes manual, my money saving wonderbook:p )