Loss of power after replacing MAF sensor

Sedoy · #1 01-09-2009, 04:57 PM

Hey guys,

Did anyone experience loss of power or hesitation during acceleration after replacing MAF sensor? I replaced my MAF sensor, which I bought from eBay for $50, now occasionally I feel big “gaps” during acceleration - power goes away, then it comes back after second or two, so X5 jumps forward slightly and pulls normally until it repeats again. Sometimes I experience it few times per day, sometimes X5 drives normally for days.
I replaced MAF sensor because I had SES with P0171 and P0174 codes. I tried cleaning MAF sensor ande intake but it didn’t work. Then I found that two rubber hoses on the back of the engine (oil separator/crankcase vacuum hoses) were badly decayed. So I replaced it and cleared the codes but SES light would still come back after 10-15 mile of driving. Then I bought that cheap MAF sensor just so see what happen. After erasing all codes and 100+ mile of driving SES light never appeared again but now I have that problem with acceleration.

I’m wondering if cheap MAF sensor will cause this problem. Any ideas?

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mrbmwx5 · #2 01-09-2009, 05:25 PM

you may got the bad one (MAF)

lo_jack · #3 01-09-2009, 05:32 PM

$50 MAF huh.

HPIA4v2 · #4 01-09-2009, 05:36 PM

Quote:

Originally Posted by lo_jack

$50 MAF huh.

Borrowing my friend quote:"you are not rich enough to shop at Ebay".

I was stupid enough to buy Adobe CS3.3i for $800 (retail from Adobe is $1300), got pirated copy, fought with Payapl and finally get Amex involved to get my money back.
I am done shopping at Ebay.

Sedoy · #5 01-09-2009, 06:12 PM

Hmm... Strange, if it is bad how come SES light went away? Maybe I should plug old MAF back and see what will happen…

Quote:

Originally Posted by mrbmwx5

you may got the bad one (MAF)

lo_jack · #6 01-09-2009, 07:02 PM

Yeah try putting the old unit back in. Leave it for a while. I forget how long it takes the ECU to relearn under new operating conditions without flashing it.

Odds are the information from the MAF is just spotty, like the performance. The contacts might not be tight from the sender. But, I think it is pretty obvious that if the only thing you changed was the MAF, and you get erratic behavior, then it's the garbage MAF. Keep it around to limp on if you need it but I wouldn't trust it.

There is almost no way I can conceive of that the separator hoses would cause the issues you have described.

There is nothing wrong with Ebay if you know what you are getting and you know why you are paying what you are paying for it. He took a gamble to try and save $250 and it looks like it somewhat worked, and somewhat didn't.

Sedoy · #7 01-09-2009, 07:39 PM

So both of my MAF sensors are bad correct? Original one because it was giving me P0171 and P0174 codes and new one because it is cheap.

Quote:

Originally Posted by lo_jack

Yeah try putting the old unit back in. Leave it for a while. I forget how long it takes the ECU to relearn under new operating conditions without flashing it.

Odds are the information from the MAF is just spotty, like the performance. The contacts might not be tight from the sender. But, I think it is pretty obvious that if the only thing you changed was the MAF, and you get erratic behavior, then it's the garbage MAF. Keep it around to limp on if you need it but I wouldn't trust it.

There is almost no way I can conceive of that the separator hoses would cause the issues you have described.

There is nothing wrong with Ebay if you know what you are getting and you know why you are paying what you are paying for it. He took a gamble to try and save $250 and it looks like it somewhat worked, and somewhat didn't.

Big "J" · #8 01-09-2009, 08:02 PM

Try putting the old one back in and see if your hesitation goes away. po171 and 174 codes are lean codes at your o2 sensors, pre-cat.

With decayed CVV hoses you may a bad CVV now and have some fouled plugs that need cleaning or changing. The CVV may need to be changed as well. Pull some plugs and check for black stains/heavy oil residue.
On the flip side the O2 sensors may be fading on you and need replacing.

Sedoy · #9 01-10-2009, 12:41 AM

Thanks for the info, I installed old MAF sensor and got SES light back I'm sure codes are the same. But no hesitation in acceleration, I will try to drive with old sensor for few days to see if hesitation comes back.

Quote:

Originally Posted by Big "J"

Try putting the old one back in and see if your hesitation goes away. po171 and 174 codes are lean codes at your o2 sensors, pre-cat.

With decayed CVV hoses you may a bad CVV now and have some fouled plugs that need cleaning or changing. The CVV may need to be changed as well. Pull some plugs and check for black stains/heavy oil residue.
On the flip side the O2 sensors may be fading on you and need replacing.

Whoopitupinmo · #10 01-10-2009, 08:23 AM

Same thing happened to me. But when I installed the new MAF I received new codes P0158 and P0160 the original codes went away however, but I most of the time got hesitation on acceleration. I kept the new MAF in for 3-4 days and it kept getting worse. What is strange is the original P0171 and P0174 codes did clear and did not show up with the new MAF in. Only the new codes appeared. We put the old one back in, car runs fine with old one, but once again thru the P0171 and P0174 codes.

Any help would be appreciated. I too think we got a bad MAF but I could be still fighting a vacuum leak I hear. Is there an aftermarket "Smoke" test that can be bought??

Thanks

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