'01 S60 T5 104k

I'd complained my new-to-me S60 suffered from annoying surge/hesitation on light acceleration especially when the A/C is on, or if the car has sat hot, and is then restarted.

Stable idle, and good performance under heavier throttle, however.

I cleaned the MAF w/ MAF spray cleaner and it's 90% better, though some hint of surge/hesitation is present. It feels like a slightly lean condition.

The consensus is that this is due to a failing ETM which has not yet failed badly enough to be replaced under warranty (my unit has one year left on warranty).

Since the MAF senses only a small percentage of the total airflow through the air pipe in which it is mounted (and extrapolates the total air-mass flow from this), it would seem one could "fool" the ECU into running a tad richer (the Oxy sensor will allow only so much of this foolishness of course) by blocking some of the air flowing AROUND the MAF (rather than through it), so more of the total flow goes through the MAF, which then thinks it's seeing a greater total flow through the pipe than it actually is.

This should result in longer injector pulses, and a slightly richer mixture.

A small aerodynamic "plug" that conforms to the inside radius of the pipe, and intrudes into the pipe should be able to accomplish this, though it would take some experimentation to get it right. Being able to monitor live data from the Oxy sensor would of course be helpful.

Another way to accomplish the same thing might be to piggyback a resistor into the intake air temperature sensor, as simulating a colder temperature should slighty richen the mixture as well. This was a trick we used years back with BMWs, and it was quite effective.

One would need to be alert for a MIL showing the fuel trim showing the mixture has been richened too much, of course.

I'd be curious to know if anyone has used such a "dodge" while awaiting an ETM failure, or for any other reason.

Bob