1998 S70 Misfiring and Stuttering/Vibrating

[Steve Ivins]

Will these cars even do 110 mph?

My 95 850 T5 and 98 C70 will go faster than 240 kph (148 mph) Overtaking a semi with two trailers I regularly exceed 160kph (100 mph) by the time I pass.
The T5 has a 19T and Lucky's blue tune and the C70 is stock. Both engines are 2.3 HPT and fuel is 98 octane plus 20% Toluene. So 110 mph is an easy feat any day of the week! I SUGGEST YOU PUT YOUR FOOT ON THE ACCELERATOR (THROTTLE). Cheers Steve.

[Steve Ivins]

Will these cars even do 110 mph?

My 95 850 T5 and 98 C70 will go faster than 240 kph (148 mph) Overtaking a semi with two trailers I regularly exceed 160kph (100 mph) by the time I pass.
The T5 has a 19T and Lucky's blue tune and the C70 is stock. Both engines are 2.3 HPT and fuel is 98 octane plus 20% Toluene. So 110 mph is an easy feat any day of the week! I SUGGEST YOU PUT YOUR FOOT ON THE ACCELERATOR (THROTTLE ,GAS). Cheers Steve.

[precopster]

Non turbos don't blow valves guys; they're way too reliable to do that.

[E Showell]

I burned a valve on my non-turbo at about 85 mph on the highway in 4th. I've got a normally-aspirated engine so I'll be waiting quite a while for the "boost to kick in" on my way to 110 mph.

[erikv11]

LOL nice Mike.

I know these case studies of one are meaningless without a very large collection of them but here's mine ... The burnt valve I have experienced was also in an NA, it hiccuped just sitting at a stoplight, even lower stress than 85 mph. Much worse than that, the replacement engine broke a valve spring, puttering around town, talk about bad luck!

[E Showell]

I have a totally speculative, unscientific, not-empirically-verified, theoretical, untested belief that as these cars age, the valve stems seals degrade leading to eventual burned valves. I use hi-mileage Mobil 1 10W30 for my oil changes (which, of course, I do myself) and the hi-mileage boast of additives to condition older seals. I wonder whether those additives are doing more harm than good?

I'm not sure of anyone I know either taking the time on a DIY basis, or hiring out the job of a complete valve stem seal replacement on an otherwise fully functional vehicle.

[erikv11]

I'm with ya, I subscribe to the valve stem seal theory.

In fact many people advocate and have done DIY valve stem seal replacement as a preventive measure, several threads about in the forums. I don't think I will have the gumption for it the next time one of mine starts smoking, these cars are getting old now, but we will see.

[E Showell]

Any way to replace the valve stem seals without pulling the head?

[erikv11]

Yes, there are a couple DIYs out there for just that, it is the only way I would do it. The keys are the right tools for the seals and a method to keep the valves from falling into the cylinder, either rope or compressed air. Pulling the head should be pretty straightforward but in my experience is opening a big can of worms. They never go back on the way they came from the factory.

[E Showell]

I've pulled a head once with my brother's able assistance. It wasn't pretty. Although now I've got a much better idea of what I'm getting into having been down that road before. . .