99 V70 Non Turbo I have had a slight stumble on acceleration lately. I decided to change the plugs.
The local auto parts store suggested Bosch Platinum +2 Part #4303. After changing,
the car ran like crap, I checked everything including removing and reconnecting the plug boots, securing everything good. Still crappy, with the check engine light coming on intermittently. I changed them one at a time so nothing got mixed up. Eventually I put the old plugs back in, and the car runs fine.

I think I may not have torqued the new plugs down enough. I have changed many plugs in my day, but the head of this car seems to be aluminum, so I just snugged them up + a little bit. Does this sound possible?

Thanks

I always just get the Volvo plugs, I think they're the best. Did you check the gap on the plugs?

No gapping on the Volvo 3 electrode plug for 1999 non-turbos. Use a little anti-seize on the threads. Seat the plug finger tight and add 1/8th turn. Kira

So much for my theory, I tightened them at least that tight.
Why would it run like crap with new plugs, but run fine with the old plugs?

The plugs are non gap able. Te factory plugs i removed look the same. I think it is a torque issue, just wondering if anyone has had the same problem.

The platinum plugs are junk. You probably got the wrong kind.

Volvo OEM last for about 50K miles, well worth the money.

The torque value is around 18lbs, but I just snug them down after putting anti-sieze on them.

Klaus
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Proud owner of a 220S. If I had more room, I would have more Volvos.