Seek diagnostic opinion regarding engine codes any encodes

[CTVoss]

Here's an easy one, probably.

I have an 1996 Q45, 115,000 miles, frequent oil changes. New spark plugs.

Around the time a check engine light came on I noticed the following change in performance: About once a week, the engine would seem to stumble, just for a couple seconds, and then return`to running normally.

This has continued for about two months, the same very infrequent brief hesitation, as if the engine was not firing for a second or was low on gas. It always recovers and continues on with no further symptoms.
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Engine codes: P0100: mass airflow or VAF sensor circuit malfunction; and P0325 knock sensor circuit malfunction.

Steps taken: I removed and cleaned the mass airflow sensor by spraying it with a can of CRC electronic parts cleaner. I also cleaned the wiring harness plug with the same cleaner and applied dialectic grease.

Result: no change. Same codes remain. Engine "balking" still remains.

If you have a diagnostic opinion or insight regarding the above presentation, I would value your thoughts greatly..

[Infinitiexpert]

My best guess is that one of the injectors or coils is bad, but I need more information to diagnose the problem. Also it could be excessive carbon built up on the cylinder (very common problem on the 96 Qs)

When the problem happens.

Is the engine cold or warm up?

If you erase the light, does the light comes back ON when or after the problem occurs?

Do you remember if the problem and code was there before replacing the spark plugs?

If the problem is not consistent, and before replacing any parts, try to perform an injector flush and a carbon cleaner flush (I'm not sure if that is the name, but is the kind of flush that cleans or tries to clean the engine from carbon built up)

[CTVoss]

Thank you for your much appreciated insights.

In response to your questions and for those who may be interested or have a similar problem here is my reply:

1. The problem does seen to occur within the first five minutes of starting the engine. I live on the West Coast were ambient temperature when the problem occurs is usually 45° to 65°F.

2. If I erase the check engine light, the light comes back on after several weeks. I believe that the problem occurs about once a week, and the check engine light may not come back on until more time has passed.

3. Yes, the problem and the codes preexisted the spark plug change.

Thank you for your suggestions regarding the injector flush and carbon cleaner flush. The hesitation problem that I described does have the characteristic of an engine running out of fuel, but it is momentary and only one time have I had to restart the engine because of a stall.

[Infinitiexpert]

1. Since the problem only occurs when the engine is warm up, I'm leaning more to a bad injector or coil.

2. I don't think the codes are related to the problem. Do not replaced the knock sensor or the air flow meter for this problem.

3. Is good to know, you may discard the spark plugs as a possible cause of the problem.

I suggest doing the injector flush and carbon cleaner flush first, it is probably the most inexpensive thing you can for an intermittent problem and it may improve the engine performance anyway.