db4690, I agree. however, with my limited knowledge of mechanical stuff. I could not be 100% sure it wasn’t the piston rings. I wanted to cover all my bases and get the correct fix before spending more $$$. This is why I came here, I knew I could get 2nd, 3rd, and 4th opinions and make a sound decision.
MY2CENTS, it sounds like you know a little bit about these engines. Are the GM 3800 Series 2 V6 engines reliable? I know every engine is gonna have it’s problems after 19 years, but overall? If you could pick a engine for long term reliability, would you choose this one or another one, like a Toyota or Honda built engines.
A leak down test on that cylinder would confirm whether or not it is the valves. If it were my car I’d probably do the leak down test at this point; but given what you say OP, it is probably a reasonable bet that the head is going to have to come off anyway, so doing a leak down test may not be a very good use of your money.
At only 85k, I don’t think that replacing the valve will unseat these rings. I have seen that happen many times, but on engines with 150k or more (back in the 60’s and 70’s, 100k). In these cases, the rings are close to the end of their service life and the sudden increase in compression puts them over the hill. I think you will be ok on this one.
Feel free to use synthetic if you want, it won’t hurt. I have switched to synthetic in engines with 100k+ on them without any issues.
Another thing to consider is that back in the 60’s & before, compression rings were cast iron with no facing material. Later they went to chromium faced and then to molybdenum faced which made them last a lot longer. I assume late models still use moly faced rings but I haven’t seen that subject come up in quite awhile.
I assume late models still use moly faced rings but I haven’t seen that subject come up in quite awhile.
This isn’t a late model car. It’s almost 20 years old.
I know you provided compression readings, but before I touched a compression gauge I would look at a lot of engine data that’s provided on the scan tool. I would want to know which specific cylinder(s) was misfiring and how often, I would want to know if there are any vacuum leaks, I would want to know how far (if at all) the fuel control system was running the engine richer or leaner, and whether the engine misfire changed with engine temperature.
“This isn’t a late model car. It’s almost 20 years old”
It is a late model relative to when moly faced rings came out which was at least 40 years ago. That post was addressing keiths and JoeMarios posts about replacing valves causing rings to unseat on engines from the 60’s & 70’s.
I have seen this with cars with moly faced rings, but at much higher mileage than in the old days of cast iron rings, that is why I posted the mileage difference. Since I now own a Subaru, I spend some time on a Subie forum. Subaru’s are famous for needing head gaskets at around 100k and sometimes new valves too. It doesn’t seem to hurt them if the rings are not done at the same time.
It seems most Subaru owners either put in another engine at the second HG change or junk the car. I haven’t seen any posts addressing this.