Cheap MAF sensor?
 

Hello all,

My 2005 H2 with 110k miles was having serious power issues and I went ahead and replaced plugs, ignition wires and MAF sensor...

Started the vehicle and scanned it. 0 codes and no more cylinder misfires.

As soon as I took it for a test drive, it felt like a new car, smooth acceleration and lots of power!

After about 3 miles, it went back to having the same problems. Scanner shows no codes, no misfires but reads MAF 0.2 lb/s at any speed.

Could it be because I bought a $32.00 MAF sensor off eBay? Local (non specialized) mechanic says it is weird that removing the MAF plug doesnt help as he insists my H2 engine should run fine even with the sensor unplugged (actually it is not driveable at all with the sensor unplugged).

Thanks!

The cheap parts are just that, and you take your chances with them. I would opt for an OEM MAF. Your mechanic is correct, it should run fine with the MAF uplugged although it should set a code and the CEL will be illuminated. Was the original MAF giving the exact same reading? I fixed a MAF code on a Bonneville by replacing the MAF pigtail. It had a broken wire right where the wire entered the connection and was not visible until I peeled back the insulation.

Make sure the intake tune is on correctly. It tends to slip off on the bottom side of the throttle body.

Tim

Good call..... if you have big enough intake leak (free air coming it) it generally will not run or will just barely run. On removing the air filter or MAF all the pulling on the tube will often pull it partially off of the throttle body. Another disastrous effect of an intake leak is it sucks grit (dirt, sand, leaves, etc) into your intake which scores up your cylinder walls and can cause high oil consumption. That was a big problem in (not on our H2's though) certain air filter housing designs where one edge of a cover blindly hooks into a slot and the other side clips. Many miss the blind point and the cover looks installed but is loose. Had a used CTS that went through a quart of oil a week due to that.

It will run fine without the MAF plugged in if everything else is correct,

Unplugging the MAF puts it in open loop and it runs off the tables in the ECM and feed back from the sensors but will not adjust fueling per the 02 sensors.

If the MAF air flow is not changing there is an issue and it needs to be repaired but also you need to figure out what the issue is causing it to act up while the MAF is unplugged.

Has the ECM been re-flashed or has it been tuned?

Neal

Also have you checked the inlet air temp on the scanner to see that its not way off?

I had the same misfire issue. But i wasnt losing power and it wouldnt throw a code for like a month. My mechanic kept on cleaning the MAF. And when i would leave the garage it would be fine for a few kms and then start misfiring again. I wanted him to look at the intake gaskets and he wasnt listening. So i ordered a set of steel fel pros and installed them. Hasnt misfired since

Hello Neal,

I don't know as I have had no contact whatsoever with the previous owner. How can I find out?

Hans .

Only way you will be able to determine if it has a non-original tune/flash on the ECM will be to use a higher end tuner like EFI Live, HP Tuners, or a GM Tech2.

One way to check for intake leaks is to remove the upper beauty cover from the engine, start it up and let it idle, then spray around the edges of the intake, throttle body, injectors, fuel pressure regulator, PCV tube, etc and if the idle changes in a spot, there is a leak. Do this when the engine is cold and do NOT get any spray on the exhaust manifold. You can use a can of carb cleaner or even a propane torch (NOT lit obviously I hope). Do this outside and good idea to have a fire extinguisher handy. A fire is unlikely but better to be safe.

These mention what I'm talkign about. I've done it a dozen times myself....
https://www.jalopyjournal.com/forum/...sting.1032664/

One of the issues on our engines (and all GM LS engines) with the plastic intake manifold is the intake manifold gaskets can harden and deform causing small intake leaks.