1997 850 with misfire, low compression - advice?

thedancingfiddle · Post by **thedancingfiddle** » 01 Mar 2020, 11:04

Ah yes, I was going to ask about that next. I wish it had more power on the hills, but mostly I don't used it for hauling lots anymore, so it's ok. Hopefully it hasn't caused any major problems since I've been driving it like this since last sept, without unplugging the injector.

Post by **erikv11** » 01 Mar 2020, 11:23

The injector spraying into a dead cylinder leads to fuel washing into the oil which will reduce its viscosity and may accelerate wear on the engine internals. So that's a long term wear issue. I wouldn't sweat it, for example the compression numbers are still (mostly?) good. but go ahead and unplug it when you get a chance.

About those compression I guess I would put it back together, drive it to warm it up and re-check for dry compression numbers on 4 and 5. Well, get numbers for 1-2-4-5. If 4 and 5 remain significantly lower than 1 and 2 then maybe some cylinder wall scoring has occurred, would be good to know that clearly if you are considering repair options.

Another thing fuel in oil might cause is engine bearing wear, not sure what else to consider.

thedancingfiddle · Post by **thedancingfiddle** » 01 Mar 2020, 11:56

Ok, I'll unplug it and continue driving for now, thanks!

Way back in Sept, I did actually try unplugging the injector on #3, when I was thinking the injector might be part of the problem, and it ran noticeably worse with it unplugged. Because of this, hopefully the cylinder wasn't/isn't totally dead, and minimal unburned fuel was getting in the engine.

Since I don't actually have a compression test gauge, I can only do this when it is nice and sunny out, the gauge the auto repair shop loans out is available, and I have the time. We'll see when those things align next

But I might just leave it as is anyway, and not sink any more money into the car. Since this isn't my only car anymore, and I'm not putting 25k miles a year on it like I have been for the last 5 years, it might last quite a while. In a couple years, $2000 could get me something quite a bit newer. Or, maybe it'll just be that much harder to find the car I really want. (aka, this car)

thedancingfiddle · Post by **thedancingfiddle** » 23 Mar 2020, 06:57

Hi all,

The car continues to run as is, and I'm wondering if I should worry about taking in on a longish trip, like 4000mi. Isn't the nicest to drive, but this trip would be mostly all highway and not many big hills. What do you think? is it risky? I might not have any other good options at the moment.

Thanks!

Post by **abscate** » 23 Mar 2020, 08:12

We had someone here drive 10,000 miles plus on 4 /5 cylinders with no ill effects. Take your speed down a notch and keep the loads low. No trailer towing.

Quick calculation.
25 mpg means each hour at 60 mph is about 2 gallons of gas burned, so 400 mL of gas into oil. If the oil level doesn't change, that means the gas is getting vaporised and burned in the PCV pretty effectively, or is burning in the cat. 6 ml of gas per minute into the cat doesn't sound like too much. Same heat content as about 4 light bulbs.

thedancingfiddle · Post by **thedancingfiddle** » 23 Mar 2020, 08:42

Thanks for the reassuring note

Definitely won't push the speed. I've got the injector unplugged, so theoretically there isn't gas getting into the cat at all now, right?
And during the few months before I knew what was going on and drove it with the injector still on, the oil level seemed to continue to decrease about the same rate as it always has, about 1qt/1000-1500 miles. I'll make sure to have a bunch of oil with me on the road!

Post by **abscate** » 23 Mar 2020, 08:50

Keep that level up. The other thing that could happen is the gas dilutes the oil and it burns faster. As long as you replace, thats ok

A liter every 1000 miles isnt too bad.

Post by **erikv11** » 23 Mar 2020, 09:09

thedancingfiddle wrote: ↑23 Mar 2020, 08:42 Thanks for the reassuring note Definitely won't push the speed. I've got the injector unplugged, so theoretically there isn't gas getting into the cat at all now, right?
And during the few months before I knew what was going on and drove it with the injector still on, the oil level seemed to continue to decrease about the same rate as it always has, about 1qt/1000-1500 miles. I'll make sure to have a bunch of oil with me on the road!

Correct, no gas is getting into the oil. Well, no more than usual for an aging engine.

Should be fine, if driven lightly you can drive it for years.

thedancingfiddle · Post by **thedancingfiddle** » 23 Mar 2020, 11:12

Would there be any reason to think it would burn less oil with thicker oil? I would be going south, potentially hot weather.

Post by **RickHaleParker** » 23 Mar 2020, 14:58

thedancingfiddle wrote: ↑01 Mar 2020, 10:49 I just did another compression test, wet test in all cylinders got me 220, 220, 62, 210, 210

Do the dry and wet at the same time because, humidity, temperature and atmospheric pressure will change the pressure reading. In other words comparing the above wet numbers to the previous dry numbers is futile.

1997 850 with misfire, low compression - advice?

Re: 1997 850 with misfire, low compression - advice?