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Changing Volvo P1800 Spark Plugs – BOSCH E7RTC

Since gotten my Volvo P1800, I have changed the spark plugs of the car a few times. The old set of spark plugs from the previous owner were changed on the 9th Oct 2021, together with the spark plug cables.

Old spark plugs from previous owner, which were dark and wet on the two on the right. I can’t recall what brand are they now, but since they look bad, so I just threw them away.

The first set were NGK BP6HS in Oct 2021, then I changed a set of NGK BP7HS in May 2022. Last week I changed two black units of NGK BP7HS that were darken.

4,3,2,1 spark plugs from last week. I changed the two on the left to two new spare that I still have.

Compared to the set of NGK spark plugs that I changed yesterday, condition of the NGK were better vs the old set from the previous owner in Oct 2021. Spark plugs 1 & 2 looks good, 3 still acceptable but 4 is still bad. Too dark, looks like not burning well.

NGK BP7HS that I changed yesterday from the Volvo. This set were used for around 3 months, except the two on the right which were just changed last week.

My car still jerk intermediately from time to time, though not too bad, but is still there. So, I decided to change the spark plugs and this time to BOSCH, which I have not tried before.

I brought the car out for a spin after changing the spark plugs. Surprisingly, it is EXTREMELY SMOOTH! I don’t feel any knocking at all, but that last for maybe just less than a minute. When I drove a little further, there is still a little weird jerking feel, though not as strong as the previous NGK spark plugs. However, there is a major change in my car: NO MORE INTERMEDIATE RADIO CUT OFF.

Intermediate Radio Cut Off

This problem has been bothering me for quite some time. My mechanic has checked the wiring, but couldn’t find any fault. He asked me to send my Volvo to car accessories shop to check, maybe they can figure out the fault.

Surprisingly, after changing the BOSCH spark plugs, the intermediate Radio Cut Off problem is GONE! I am very sure the intermediate radio cut off problem is there before I changed the spark plugs, as I have the radio ON (playing MP3 from USB) for a few days already. However, after changing to BOSCH spark plugs, the problem is GONE!

To be honest, I do not believe it. So, I set the volume of my radio to quite high, making sure that I do not miss any cut off sound while driving at higher speed (normally the intermediate radio cut off happened when I press the pedal to accelerate). I drove around for quite some distance, done a few trips buying groceries, sending kid to tuition…etc., more than 20km here and there. Today, I drove another 30km with my radio on, and I did not hear any intermediate cut off of my radio. I am pretty sure that the problem is GONE, or at least is GONE now. Since this happened right after I changed the BOSCH spark plugs, and I did not alter any other thing, so I can only give credit to the BOSCH.

What I am guessing is that…MAYBE…the better combustion of the engine via BOSCH spark plugs causes better or smoother performance of the alternator, hence delivering more consistent current and voltage to the car.

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