Flickering headlights and misfire.

[dikidera]

Today I noticed for the first time my MAF reading dipping to 3.10g/s and even below 3 on idle, I think I may have a vacuum leak somewhere but it's likely very very small. It could even be the gasket itself on the intake manifold.

[dikidera]

Well, after running my scope I have managed to capture these traces. The album is only from Cylinder 1.



And a video where I go across each cylinder individually(starting from Cyl 1 at the timing belt and moving rightwards), marked by a pause in the oscilloscope waveforms.

The most repeatable waveform is this one all from Cyl 1


This second waveform seems to indicate that resistance increased suddenly and then there was a lot of coil energy left inside.

[dikidera]

I am scratching my head, buut. Here is what I also found. Trims do become positive and poisitive trims usually indicate vacuum leak, I can see lambda(stft) going to 1.03 1.04, but hovers around 1.02, which means positive fuel compensation. Today was the first time I ever saw idle maf go down to 2.8g/s, and I can assure you it was almost always 3.8g/s on idle(no aircon no fan no nothing). But then a few weeks ago I noticed it dipping down to 3.4, then 3.2g/s and then today icing on cake, 2.8g/s with positive trims with MAP sensor showing intake manifold pressure lower than 5.8 psi I've seen other times.

When I give the car very little, very light blip of the throttle I mean going from idle pedal position of 7.3% to like 9 or something, the RPMs increase but as they go down the car shudders as RPM goes lower than 750(to like 700 or lower) and then all of a sudden idle maf is 3.2g/s(still lower than normal).

So lower idle MAF value and lower than normal intake manifold pressure, which translates to higher vacuum, if vacuum is higher, throttle is closed more than it should be? Just to remind again I have the infamous Magnetti Marelli ETM.

The positive fuel trims usually suggest a vacuum leak, but I have sprayed the entire intake system(except around PCV since it's behind the manifold) and have found nothing. If the ETM on the other hand is not reporting correct information I can see how it could affect trims.