MAF slowly going bad?
07-19-2014, 08:24 AM
#31
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Location: Gatineau, Québec, Canada
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New O2 sensor on the way.
I'll report back with new one installed.
But like I mentioned, the car idles SO smooth now!
Smooth and stable. It is just perfect.
Disconnecting the O2 sensor as bring the idle a bit higher. Exactly what it needed to stop the vibrations.
I really hope that with the new O2 sensor installed, it will stay exactly like it is now.
I'll report back with new one installed.
But like I mentioned, the car idles SO smooth now!
Smooth and stable. It is just perfect.
Disconnecting the O2 sensor as bring the idle a bit higher. Exactly what it needed to stop the vibrations.
I really hope that with the new O2 sensor installed, it will stay exactly like it is now.
07-27-2014, 12:58 PM
#32
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New O2 sensor installed.
Everything's perfect.
Smooth and stable. Just like it should.
It's been a while I've seen the idle that good!
Many thanks all - particularly John - for your help and suggestions.
Greatly appreciated.
Everything's perfect.
Smooth and stable. Just like it should.
It's been a while I've seen the idle that good!
Many thanks all - particularly John - for your help and suggestions.
Greatly appreciated.
07-28-2014, 05:53 AM
#33
Pro
Hi Bertrand,
When my MAF went sour, problems didn't occur until I had been driving for 30+ minutes.
Overall performance diminished (auto would not kick down unless forced and then upshift well below redline). Temp was up a couple of needle-widths.
On throttle over-run there was much popping and farting from the exhaust (= lean mixture).
Swapped in a known "good" MAF and vrooom.
As for low idle speed and rough running: when I refinished my intake manifold I thought I knew better and didn't use fresh Porsche rubber gaskets, instead using the old with gasket sealant. WRONGGGG! Do not pass Go. Do not collect $200.
Ratty low speed throttle response up to 1/2 throttle. Showing all the symptoms of "loose air".
Using a $10 'engine' stethoscope (nothing more exotic than a normal stethoscope with a 4" toob on the end) I probed around under the manifold (engine running) and could hear a high-pitched 'hsssssss' sucking sound. Narrowed it down to the 5/6 area.
Bit bullet and pulled manifold (amazing how quickly it can be done 2nd & 3rd time) and bingo: air leak around #6 inlet.
Re-installed with new Porsche gaskets etc and is still good 11 yrs later.
So IMHO, given the symptoms U describe, your MAF is unlikely to be going off (Boom!!! haha) but since you re-used the manifold gaskets it's possible there is a small intake manifold air leak.
Now - don't be swayed by suggestions of all sorts of hi-tech overkill analytical methods to find this 'leak'.
Stick to good basics: buy and use a simple "engine" stethoscope. No electronics. No nothing except you listening for the "Hssssssssssssssssss" sucking sound.
Go one step further: squirt some olive oil around the suspected leak and listen for a change in the sucking sound / engine idle.
If these change then away you go with manifold gasket replacement.
HTH.
UpFixen.
.
When my MAF went sour, problems didn't occur until I had been driving for 30+ minutes.
Overall performance diminished (auto would not kick down unless forced and then upshift well below redline). Temp was up a couple of needle-widths.
On throttle over-run there was much popping and farting from the exhaust (= lean mixture).
Swapped in a known "good" MAF and vrooom.
As for low idle speed and rough running: when I refinished my intake manifold I thought I knew better and didn't use fresh Porsche rubber gaskets, instead using the old with gasket sealant. WRONGGGG! Do not pass Go. Do not collect $200.
Ratty low speed throttle response up to 1/2 throttle. Showing all the symptoms of "loose air".
Using a $10 'engine' stethoscope (nothing more exotic than a normal stethoscope with a 4" toob on the end) I probed around under the manifold (engine running) and could hear a high-pitched 'hsssssss' sucking sound. Narrowed it down to the 5/6 area.
Bit bullet and pulled manifold (amazing how quickly it can be done 2nd & 3rd time
) and bingo: air leak around #6 inlet.Re-installed with new Porsche gaskets etc and is still good 11 yrs later.
So IMHO, given the symptoms U describe, your MAF is unlikely to be going off (Boom!!! haha) but since you re-used the manifold gaskets it's possible there is a small intake manifold air leak.
Now - don't be swayed by suggestions of all sorts of hi-tech overkill analytical methods to find this 'leak'.
Stick to good basics: buy and use a simple "engine" stethoscope. No electronics. No nothing except you listening for the "Hssssssssssssssssss" sucking sound.
Go one step further: squirt some olive oil around the suspected leak and listen for a change in the sucking sound / engine idle.
If these change then away you go with manifold gasket replacement.
HTH.
UpFixen.
.
07-28-2014, 06:31 AM
#34
Pro
Hi Bertrand,
When my MAF went sour, problems didn't occur until I had been driving for 30+ minutes.
Overall performance diminished (auto would not kick down unless forced and then upshift well below redline). Temp was up a couple of needle-widths.
On throttle over-run there was much popping and farting from the exhaust (= lean mixture).
Swapped in a known "good" MAF and vrooom.
As for low idle speed and rough running: when I refinished my intake manifold I thought I knew better and didn't use fresh Porsche rubber gaskets, instead using the old with gasket sealant. WRONGGGG! Do not pass Go. Do not collect $200.
Ratty low speed throttle response up to 1/2 throttle. Showing all the symptoms of "loose air".
Using a $10 'engine' stethoscope (nothing more exotic than a normal stethoscope with a 4" toob on the end) I probed around under the manifold (engine running) and could hear a high-pitched 'hsssssss' sucking sound. Narrowed it down to the 5/6 area.
Bit bullet and pulled manifold (amazing how quickly it can be done 2nd & 3rd time) and bingo: air leak around #6 inlet.
Re-installed with new Porsche gaskets etc and is still good 11 yrs later.
So IMHO, given the symptoms U describe, your MAF is unlikely to be going off (Boom!!! haha) but since you re-used the manifold gaskets it's possible there is a small intake manifold air leak.
Now - don't be swayed by suggestions of all sorts of hi-tech overkill analytical methods to find this 'leak'.
Stick to good basics: buy and use a simple "engine" stethoscope. No electronics. No nothing except you listening for the "Hssssssssssssssssss" sucking sound.
Go one step further: squirt some olive oil around the suspected leak and listen for a change in the sucking sound / engine idle.
If these change then away you go with manifold gasket replacement.
HTH.
UpFixen.
.
When my MAF went sour, problems didn't occur until I had been driving for 30+ minutes.
Overall performance diminished (auto would not kick down unless forced and then upshift well below redline). Temp was up a couple of needle-widths.
On throttle over-run there was much popping and farting from the exhaust (= lean mixture).
Swapped in a known "good" MAF and vrooom.
As for low idle speed and rough running: when I refinished my intake manifold I thought I knew better and didn't use fresh Porsche rubber gaskets, instead using the old with gasket sealant. WRONGGGG! Do not pass Go. Do not collect $200.
Ratty low speed throttle response up to 1/2 throttle. Showing all the symptoms of "loose air".
Using a $10 'engine' stethoscope (nothing more exotic than a normal stethoscope with a 4" toob on the end) I probed around under the manifold (engine running) and could hear a high-pitched 'hsssssss' sucking sound. Narrowed it down to the 5/6 area.
Bit bullet and pulled manifold (amazing how quickly it can be done 2nd & 3rd time
) and bingo: air leak around #6 inlet.Re-installed with new Porsche gaskets etc and is still good 11 yrs later.
So IMHO, given the symptoms U describe, your MAF is unlikely to be going off (Boom!!! haha) but since you re-used the manifold gaskets it's possible there is a small intake manifold air leak.
Now - don't be swayed by suggestions of all sorts of hi-tech overkill analytical methods to find this 'leak'.
Stick to good basics: buy and use a simple "engine" stethoscope. No electronics. No nothing except you listening for the "Hssssssssssssssssss" sucking sound.
Go one step further: squirt some olive oil around the suspected leak and listen for a change in the sucking sound / engine idle.
If these change then away you go with manifold gasket replacement.
HTH.
UpFixen.
.
In any case - where would we all be without both the technical excellence of and generosity of John Speake?
Cheers and thanks John.
UpFixen.
.
07-28-2014, 09:42 AM
#35
Drifting
Congrats Bertrand. Very informative thread. Jim's response to your question about the purpose of the O2 sensor on our cars is very informative. I have an old Volvo 240 that did not run properly when it needed a new O2 sensor, so I had the same question as I read your car was running perfect without the sensor.