Chasing a bad off idle hesitation/stumble on the $2k car. It came without the OEM air cleaner assembly. Instead it has a cold air tube from the MAF down to a cone filter mounted low in the bumper. It's not giving any MIL codes but has a terrible hesitation. Same with part throttle, a jab on the accelerator is first met with a hesitation and then it goes. Can this be caused by the "cold air induction?" Any way to address it without finding an original air cleaner assembly? The filter looks pretty non-filtery. I have a new K&N cone sitting on the shelf that I was going to try but figured I would check here if I may be on the right track or not at all.
There's lots of situations where a mass air sensor needs the factory air tube and box. If there is no maf, it shouldn't bother anything.
I'd check the TPS and look for issues elsewhere. It's possible it's causing the stumble, but there are a host of things that be the issue. Fuel pressure okay? Spark okay? No spark leaks from the ignition coils? Grounds good?
Streetwiseguy said:
There's lots of situations where a mass air sensor needs the factory air tube and box. If there is no maf, it shouldn't bother anything.
I haven't seen a situation where a MAF didn't need the factory air tube and box.
What is enlightening is how much fuel trims can change just from rotating the part the MAF is in by 90 degrees. Or leaving the stock airbox unclipped. Or having an air filter that is only dirty on one part of it, so the air flows differently through it.
Heck, I had a Mustang with a CARB EO'ed "cold air intake" that was 35% lean everywhere. We chased every possible reason why it could be running lean. Recalibrating the MAF transfer table corrected the issue.
On some vehicles, that resonator in the air plumbing isn't there for auditory noise but airflow noise. Replace the intake muffler in a ZX2 with a straight pipe and you will get a fat hole in the torque curve when the MAF reads screwy because intake resonances are messing with the flow reading, for example.
I suspect that a lot of the "power gains" from these things is not from colder air, or free flowing whatever, but because they bork up the MAF readings. if the MAF reads low, the engine will run a little leaner and run a little more timing, so it will make more power, possibly.
