Flickering headlights and misfire.

[scot850]

Have you checked the throttle body? There is another current thread on that with a V70R having issues.

Neil.

[dikidera]

These cant be checked so easily. They are the infamous Mangetti Marelli ETM, there's always a possibility of it being the sole cause of misfires. The ETM's TPS1 and TPS2 show a consistent 1 degree difference at idle and throughout the rev range, sometimes increasing above and sometimes being below 1 degree difference.

However I must also look at the flickering. My AC ripple test was inconclusive. I still suspect maybe part of the reason is something alternator or battery related. The battery seems to have indication of it having leaked slightly from two locations. Very slightly but still there.

I have a FM transmitter in the car which shows voltage, so I don't measure via VIDA, but it sometimes shows a 15.0 voltage reading, but mostly 14.8. Its cold now so the battery high has internal resistance, but perhaps the fact it has leaked even if very slightly, maybe it's part of the problem causing flickering headlights, cabin lights and possibly erratic voltage to the coils.

When I had replaced my voltage regulator a year ago, I had noticed that the old voltage regulator brushes were worn unevenly, and by a factor of two at least. One was significantly shorter than the other. Now I know there are slip rings on which these brushes ride, so maybe something there is responsible, additionally I learned that the diode pack is spot welded on these and not easily serviceable?

[scot850]

Your car has the Mangnetti Marelli ETM? I thought Volvo dropped those for 2003 on cars? Even the 02 XC70 I am working on has a Bosch throttle body.

I have been working with an alternator repair guy. He says that these days the quality of the voltage regulators are very poor and can last only a very short time. It does seem strange that you have one of the brushes wearing much faster than the other. If you had a bearing problem to allow that amount of movement I'm sure you would hear it.

Can you borrow a battery from somewhere to try? These modern cars really don't like poor batteries. Your alternator may be charging ok, but the battery may have a weak cell. How old is the battery?

Neil

[dikidera]

Yes, for Bifuel models, the ETM was used up to 2007.

My battery is 2.5 years old, the voltage regulator is 1.2 or so years old. Serpentine belt is also a year old.

This is how the old voltage regulator looked like. Btw, now I remember, I replaced it because of the same flickering I have now and I think maybe due to undercharging (less than 13.5v).



UPDATE:I tested with a spare battery, same flickering. I think I also should mention that for the past 6 months or more I've been hearing what I think is some buzzing noise either from the DIM or maybe the area of the CEM, it happens especially when I rev the engine at idle and let go of the accelerator but only like for a second. Additionally while driving I think but I am not sure, I am hearing some relay click just once in the area below the steering column.

[dikidera]

Well as I said in the previous post the other battery I tried made no difference. But now I need to ask, what is the proper charging voltage here? Why would I consistently see 14.7, 14.8 and sometimes briefly 15v at idle(measured by a fm transmitter dongle)? With a new-ish regulator.

Are we looking at some CEM problem here?

[jonesg]

if you take voltage at idle on the battery posts its a direct volt output from the regulator., it doesn't pass thru the cem.

[br0dy519]

What brand regulator did you use? I tried 2 off-brand and they were both DOA before I got the Bosch.

[dikidera]

Fairly certain it was a BOSCH unit. I think only an oscilloscope can accurately show me how the voltage fluctuates, but my bench oscilloscope is not useful for such an isolated system.

I spoke with someone with a V70 2.4D, he said he had the same problem with mildly flickering interior and headlights and while not completely gone he reduced it much more with a complete overhaul of the alternator. But he said while definitely reduced it was still there.

[jonesg]

Fairly certain it was a BOSCH unit. I think only an oscilloscope can accurately show me how the voltage fluctuates, but my bench oscilloscope is not useful for such an isolated system.

I spoke with someone with a V70 2.4D, he said he had the same problem with mildly flickering interior and headlights and while not completely gone he reduced it much more with a complete overhaul of the alternator. But he said while definitely reduced it was still there.

sounds right , a dead band on the commutator giving a skip.
i would just swap it out.

[dikidera]

I will have to investigate to see if this is what is affecting ignition. Another detail that may or may not be relevant at all, is that I've noticed at times, my VVT advance at idle should be 0, but sometimes it oscillates between 0 and 1 degree every few seconds or stays at 1 for a while even though it should be 0 all the time during idle.

It would be really funny if my VVT is damaged and is causing all this, or even yet the cam or crank sensor. Too many variables.