FAQ: Mass Air Flow (MAF) Sensor Issues?

I sprayed inside at the sensor with MAF sensor cleaning spray. Did that a few times and gave it some time before I started it up. . After 2 restarts the MAF kicked in and failed immediately   

Im gonna hose it with spray tomorrow and make sure its spotless.
http://www.pontiacbonnevilleclub.com/forum/2000-2005-other-than-gxp/topic26286.html

Super charger chuck hooked me up with a new MAF sensor. I am running better than I ever have before now. I never realized that a bad MAF could result in poor performance but still operate. Now that I know the power I have now I know that my MAF has been bad for a while before it finally gave out last weekend!

My riv is rollin super smooth right now. Smoother than ever before.

I need some help guys. When I first got my Riv, the "Service Engine Soon" light was on. I got a P0102 code. Keep in mind this is with the original MAF. I would clean the sensor and the car would run back to normal. A few days later the SES light would come back on and I would do the process over again. I eventually got a new MAF from a junkyard that came out of a 1998 Oldsmobile Intrique that had 142,000 miles. After replacing the MAF with the new junkyard one, everything went back to normal. No more SES light.

On my way home from work today, the SES light came on and I had O'Reilly's get me the codes and I got P0102 and P0171. The scanner said I have a lean condition. Can the MAF cause the P0171 code? What about the 02 sensor throwing up a MAF code? If It's the 02 sensor causing the MAF code, will a new 02 sensor get rid of both codes?

I cleaned the MAF and took it for a run and the SES light is still on. I used MAF cleaner too. I don't think my luck is bad enough to eat through two MAF's. I'm thinking it could be the sensor. Thoughts?

I just unplugged the MAF with the car running and nothing whatsoever happened. I wonder why I have the P0102 code? I'm kind of thinking the P0171 code also triggered the MAF code. Now to find out why the P0171 code is happening. I've checked all the vacuum lines and I don't hear, see, or feel anything abnormal. My idle RPM's are normal too. I have two vacuum lines that might be causing a problem, but again, my idle RPM's are normal and they don't look that deteriorated. Just some very small cracks. Nothing that I would think would cause a problem.

Who knew that replacing a leaky part of fuel line and a fuel filter would cure this issue. Acceleration is so much smoother now.

P0102 is mass airflow sensor low input. This could be from a bad MAF sensor, or a big vacuum leak.
P0171 is a 'too lean' code, NOT a "bad O2 sensor" code. Too lean usually happens with a big vacuum leak.

I see a common theme in your codes... quadruple check all the vacuum lines visually, especially the rubber T fittings and end fittings. You have a vacuum leak. It's possible that it's the lower intake manifold gaskets if you've never done those before but check everything else first.

Spraying a little carb cleaner around the base of the intake manifold and vacuum lines (lightly) while the engine is running will help you locate the vacuum leak. The engine will race or stumble a little when you spray near a vacuum leak. Be gentle with the stuff.

A piece of garden hose cut off to about 3 feet long will help too - hold one end near your ear and move the other end around the top of the engine listening for a hiss.

charlieRobinson wrote:

Super charger chuck hooked me up with a new MAF sensor. I am running better than I ever have before now. I never realized that a bad MAF could result in poor performance but still operate. Now that I know the power I have now I know that my MAF has been bad for a while before it finally gave out last weekend!

My riv is rollin super smooth right now. Smoother than ever before.

Charlie, what were your symptoms & did you have a code that made you suspect the MAF?

Mine has a slightly rough idle & I feel it should perform a little better, but no codes.
I have cleaned the MAF but no improvement.

I've done a laundry list of things I thought may help but nothing has.
(plugs, wires, LIM, FPR, fuel filter, ZZP matched injectors)

The MAF isn't a cheap swap to guess at.
Thanks,
Jbird

bro, mine totally just went to shit while i was driving on the highway! it was an all of a sudden thing! i was cruising around 70mph and then suddenly lost like %50 of my power! I was able to limp it home and right when I parked it stalled out!

I think i got a MAF code is how I knew it was the issue. I unplugged it an ran on the VE table for about a week before SC chuck hooked me up.

They can be cheap(ish) if you find the right seller. Otherwise people will try to rob you for them.

if your car runs the same with the MAF plugged in or not, then I'd have to say you have a MAF sensor issue. But I'm a total noob so please dont listen to me!

That s a bit more in your face!

So, I have heard others say unplug it to see if it changes.
Is it best to unplug while running, or prior to start?

VE table read at start? Or constantly once MAF is disabled?
noob too.

Jbird

unplug it before you start it. The PCM will fail over to VM table. not sure what kind of mods you are running, but it should run OK on VE.

In the meantime, try to find a source for a cheap MAF sensor.

As soon as I do my gen V swap (no ETA on this) i will have a MAF sensor for sale, but dont wait for me on that one..

KnottyEagle wrote:

Who knew that replacing a leaky part of fuel line and a fuel filter would cure this issue. Acceleration is so much smoother now.

Well, Eagle, since you asked.....
Hi guys,  I KNOW you have missed my eloquence, so I must point out that this problem is a classic example of overly depending on the computer codes to find your problem...  Eagle had codes, but they WEREN'T REAL codes!  They were caused by good 'ol fashioned filters & hoses.

I will try it.
Zero mods, first summer with the car.
I really hoped to have it 100% this season, now I'm thinking I may have to store it again & try again next summer. Won't consider any mods till I know everything is right.
Appreciate the heads up, I may be still looking when you are ready to move it.
Thanks,
Jbird

I am having one hell of a time with these codes. Again on my way home from work, my SES light came on. I stopped at Autozone and got four codes this time around! P0102, P0171, P1811, and P1672.

How do I check for a bad MAF? Unplug it while the car is running and if nothing happens, It's bad?

This is frustrating. I haven't really noticed any power loss or MPG loss. All I've really felt is a delayed shift time. The code P1811 says that the ECM has detected this. I think this code is present because of the P0102 code. I actually think all of these are happening because of the P0102 code, which is happening from something else...probably a vacuum leak, which I still need to check for.

The P1672 code sounds unrelated though. It's for "engine oil level lamp control circuit fault". This code doesn't bother me. I know my engine oil level is perfectly fine.

You should find and fix your vacuum leak, clear all codes, and see what comes back.

When you turn your key on the dash lights should all come on for a self test. Do you see the red 'oil can' light?

deekster_caddy wrote:

You should find and fix your vacuum leak, clear all codes, and see what comes back.

When you turn your key on the dash lights should all come on for a self test. Do you see the red 'oil can' light?

No kidding.

Both the oil can and "check oil level" lights come on.

Pretty sure now that this is a LIM gasket problem. I looked around the back of the engine as much as I could and It's a little wet back there and the injectors are looking sludgy.

That could be a leaky valve cover gasket. LIM gaskets often leak internally, without any visual clues. Best way to know is to pull the plugs in suspect cylinders and look for residue. Or send a sample of oil to Blackstone for analysis. They'll detect coolant in the oil, if any.

AA wrote:

That could be a leaky valve cover gasket.

It could, but VC gaskets don't generally leak "up". More than likely the spark plug boots would be covered in goo, and the heads and tops of the manifolds would be wet.
Almost every single 3800 I've seen with the Injector holes sludgy and what-not comes from the LIM. Also, simply sending in the oil to have checked isn't necessarily going to prove that the LIM is leaking. They leak externally also....the internal leak is just another symptom.

Just sayin....


If I were you Knotty, I'd pull the entire upper half off and replace the LIM and VC gaskets anyway, and probably toss in a new set of Injector O-rings. This way, you know it's done, and there aren't anymore "what-ifs". If you're planning on keeping this car, it's a very wise investment of your time to replace that stuff.

Good points, and agree with the solution. In my own experience, the LIM leaked internally with no visible warning. Plugs and oil analysis confirmed. Still, even with that knowledge it was such a minor leak (coolant was never low) that I waited till rebuild time to fix. Frequent oil and plug changes got me by for a very long time.

The problem with the LIM replacement is the inconvenience. Even though it's relatively easy to do, not everyone wants to dive into a job like that. Knotty, if you are so inclined, I'd do it. Your car's mileage suggests it might be time!

update,
I pulled the plug on my MAF & it seemed to idle ok.
I took it out for a spin & the motor seemed to sound better, quieter /smoother during acceleration.
Thinking it could be my imagination/hope, I picked up my brother extending the test drive.
He seemed agreeable that it showed noticeable improvement.
Purchased my new MAF today from the dealer.
Does NOT seem to have helped.
Not sure where to go from here, still no codes but I feel like the car just sounds loud/labored when accelerating & idle is mildly rough.
Is there another sensor that is disabled while the MAF is disconnected that could be affecting performance, that could be negatively affecting performance when back in the loop?
I keep throwing/wasting money to try & get it resolved, not sure what else to do without any codes to lead me in the right direction.
Any ideas?

jbird wrote:

Charlie, what were your symptoms & did you have a code that made you suspect the MAF?

Mine has a slightly rough idle & I feel it should perform a little better, but no codes.
I have cleaned the MAF but no improvement.

I've done a laundry list of things I thought may help but nothing has.
(plugs, wires, LIM, FPR, fuel filter, ZZP matched injectors)

The MAF isn't a cheap swap to guess at.
Thanks,
Jbird

jbird wrote:

update,
I pulled the plug on my MAF & it seemed to idle ok.
I took it out for a spin & the motor seemed to sound better, quieter /smoother during acceleration.
Thinking it could be my imagination/hope, I picked up my brother extending the test drive.
He seemed agreeable that it showed noticeable improvement.
Purchased my new MAF today from the dealer.
Does NOT seem to have helped.
Not sure where to go from here, still no codes but I feel like the car just sounds loud/labored when accelerating & idle is mildly rough.
Is there another sensor that is disabled while the MAF is disconnected that could be affecting performance, that could be negatively affecting performance when back in the loop?
I keep throwing/wasting money to try & get it resolved, not sure what else to do without any codes to lead me in the right direction.
Any ideas?

Is there a loud hissing noise to accompany the 'labored' feeling? Could be a clogged cat, wouldn't be the first. But there are other things to look at first.
First and foremost, check for vacuum leaks. Check more than once. Check more than twice. Visually, with a stethescope, and by feel. Get in there and touch all of the little rubber T connectors and end to end connectors on the vacuum lines all around the motor. The rubber connectors are notorious for drying out and cracking.
When you replaced the FPR, did you set the fuel pressure? At idle, with it's vacuum line removed and plugged, you should have 50 PSI.

I have wondered about a clogged Cat, but unsure how to diagnose.
There isn't a "hissing" or tick, it just sounds louder than it should to me.
When I rapidly accelerate my Regal, 3800 NA, it goes smoothly/with sounds from the rear(exhaust)
not the front.
I have looked/checked for vacuum leaks & so did a mechanic friend, but I agree that another look would not hurt.
I did not set the pressure when I replaced the FPR, didn't know to.

If you have a infrared thermometer, you can test to make sure your cat is working properly by measuring inlet and outlet temp of the converter. A working cat will have a HIGHER temperature at the immediate outlet. If the temperature is considerably higher before the cat, it is either failed or clogged. You could also take it for a ride and run the car at highway speed in third then immediately park it and look at the exhaust. A clogged cat can glow red if it is restricting enough. Harbor freight sells infrared thermometers for like $20.

Closer inspection around the injectors today and I can see some more sludge build-up around the front three injectors and also what looks like some orange sludgy stuff. Probably old Dexcool. I know the previous owner said "and I got rid of that orange crap in there". Or, you just never changed it.

So, while I'm doing the LIM gasket, I should do the valve cover gaskets too? What about the upper intake manifold gasket? Does the Fel-Pro gasket set on RockAuto have everything for doing the LIM gasket?