My SES light is reading that my Mass AirFlow sensor is bad but...
if the car sits for an hour or so, the car starts up and runs fine. but if i shut it off and restart (immediatly or within 45 mins) it bairly runs.
Do i need to clean it or soemthing or is it shot?

 

Best way to check for a bad MAF is to tap on it lightly (don't beat on it but good taps) with a screwdriver of such while the car is idling. If the motor fluctuates when you are tapping on the MAF housing, then the MAF is bad. The tapping should not do anything to motor reaction if the MAF is good.

Its a trick a professional mechanic friend with 40years in the business has taught me to help trouble shoot this motor.

 

And it works!

 

i already tried that and the motor doesnt fluctuate at all. which means its good but it still runs horrible

 

Check for a vacuum leak.

 

make sure all the pieces of ur intake ducting is attached properly and there arent any holes in the system.

 

Remember, the tap test only works if there si a vibration related problem in the MAF, if you have something internally that's shorted or grounded and isn't affected by vibration(like a toasted diode or something) then you'll always show a good MAF with the "tap test".

On something like that, I would start to look for leaks and things that let extra air into the motor.

What is the actuall code umber that you are getting? There are 2 for the MAF I think, one for if it's reading higher than expected, one for lower or the circuit being open, shorted, or grounded.

Something else to look at is the ECT. I know it seems totally unrelated, but when you first start the car up, this sensor, paired with the MAF, are what control injector pulse width in open loop. Sometimes our computers get confused because one sensor is reading worng, but the way it's programmed makes it set a code for something that seems unrelated.

 

It is reading a code 32 (which is has been for a month or so now) and code 34 (it just started to this week).
I broke the solenoid thats connected to the vaccum lines when i was owrking on it before, so i replaced it and ive been gettin code 32 ever since. I am going to pickup a new one of those today and see if it helps.

 

i've been having the same problem, but you are talking about the solenoid back on the passenger side by the coil, correct, if not what is it called that has one vacume line going in and a bunch of wires atop of it! still getting a 32 and 34

 

OK, that helps to clear up a couple things. The code 32 is for the EGR system. The way that the system works is that the ECM commands the EGR to turn on and off to get a certain amount of vacuum. So, say if the engine was pulling 20 inches of vacuum and the EGR only needed to go up 1/2 way, the ECM would command the solenoid to a 50% duty cycle and give the EGR 10 inches of vacuum (I don't know what the actual vacuum requirments are, that's just an example.)

Now, here are the things that will cause that code. A bad solenoid, an bad vacuum line in the EGR system, and bad sensor, or a bad EGR Diaphram.

The Code 34 is High Vacuum at the MAF sensor. For whatever reason, it's showing a higher than expected amount of vacuum (low air flow) at the MAF.

Now, you'll have to ask TomP to look in his GM service manual, but it sounds like the 2 problems might be realated. My theroy here is that the ECM uses the EGR Vacuum Sensor on cold start to get the outside barometric pressure for a startup pulse width. It might also use it while you are at cruise to verify proper operation of the MAF becauase there is probably a mathmatical way to figure out how much air SHOULD be flowing through the MAF, based on engine RPM and vacuum.

But as far as the start up theory goes, when you turn the key on, the ECM opens the EGR solenoid all the way to allow ambient pressure to the sensor, that way the ECM knows what the pressure is when you crank the engine. Then once the enigne is started, it should be able to calculate how much air should be going through the MAF at idle right after startup. So if the Sensor is giving the ECM a crap signal, you would get the cold start problems that you are talking about, a MAF code because the amount of air the MAF says is coming in isn't what the computer calculated based on the sensor reading, and an EGR code when the ECM looks at the sensor to see if the solenoid is working properly.

Wow! That's a long, technical post, huh? Long story short, I think your EGR solenoid and/or sensor is crap.

 

i am throwing a 24 and i think a 43 too. don't know what the heck is going on with it.