Quote:
Originally Posted by blue62
Unplugging your MAF senor to check MAF sensor condition is not a very reliable test of the MAF sensor.
Yes it seems to work if your sensor is bad.
But by unplugging it your not really testing it.
What if you have a vacuum leak?
A vacuum leak can cause lumpy idle, it is a lean condition due to the unmetered air.
When you unplug the MAF the DME reverts to a default fueling strategy based mostly on engine load and RPM.
That default fueling strategy is biased on the rich side which compensates for the lean condition, so the car idles and runs rather well with a vacuum leak and the MAF unplugged.
Plug the MAF back in or replaces it the car again idles lumpy because in this case it was a vacuum leak.
So now in this case you have spent what over $200.00 on a new MAF sensor and not fixed the lumpy idle.
Much more reliable ways to test the MAF.
Fuel trims and comparing Throttle Position Sensor signal to MAF sensor signal are two means.
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you're not wrong on any of that, Blue, but I feel like you're barking up a tree which doesn't get much attention because it's so uncommon.
As you say; there are ABSOLUTELY more reliable ways to positively-test a MAF, but none as easy to narrow-down what's going on. Basic Troubleshooting 101 says
see if you can produce a change in the symptoms. If unplugging the MAF produces a change in symptoms, then you are one step closer to understanding what's REALLY going on.
We're chasing cam solenoids and timing, without (seemingly) to have checked some of the (honestly more likely) easy and cheap items.
Vacuum leaks are VERY common, of course; but how many of them will show up only during closed-loop, or open-loop? Most of them will be causing the same issue regardless.
Again; y'all can chase whichever squirrels you like, but the OP asked for some suggestions. I'm simply suggesting that the easiest and cheapest things shouldn't be overlooked in favor of something more complex, for no apparent reason. Especially when the more complex things have been checked and seem to be correct.
