xc90 2.5t with dead #3 cylinder

hoboken · Post by **hoboken** » 05 Feb 2020, 10:22

i have a 2004 xc90 2.5t with dead #3 cylinder(low compression) how far could i drive it ? 500 miles? and if i do do i need to be worried about loading the catalytic converter with gas and starting a fire? and if so is there a way to turn of the gas to #3 cylinder?

Post by **RickHaleParker** » 05 Feb 2020, 11:17

hoboken wrote: ↑05 Feb 2020, 10:22 is there a way to turn of the gas to #3 cylinder?

Disconnect the wiring harness from injector #3.

wanderdüne · Post by **wanderdüne** » 05 Feb 2020, 11:26

How low is the compression on cylinder 3? And do you know why?

But yes, one could unplug the injector and the coil pack and run it if it had no compression, but probably it would be a good idea to unplug the injector, remove the spark plug and also the coil if there is any compression in the cylinder. I think that if the spark plug were left in and it had some compression, it would send too much air to the cat and make it run hot. Probably would sound a little crazy while running, but hey. The more modern cars that cut a cylinder for fuel economy also relieve the compression through the valves along with other computer adjustments.

Disclaimer: I'm not saying this is a proper thing to do, it's just a theory. This is just my opinion, not advice. Running a car with a dead cylinder could be dangerous for a variety of reasons. What you do to modify your vehicle is your choice.

hoboken · Post by **hoboken** » 05 Feb 2020, 11:58

wanderdüne wrote: ↑05 Feb 2020, 11:26 How low is the compression on cylinder 3? And do you know why?

26 psi with all other plugs pulled on #3. dealer put a camera in cylinder and said it had a chipped valve.
i should also say it has 215k on milage

Post by **cn90** » 05 Feb 2020, 21:36

My 1998 S70 GLT burned valve #3 at around 180K miles (this was in 2018).
I unplugged the wiring connector to fuel injector #3.
At idle, car was vibrating a bit but at highway speed, it is hardly noticeable.

Then the trans lost reverse at 188K miles, that was when I ditched the car.

So, yes, unplug #3 and turn that into a "grocery getter"...

Post by **SuperHerman** » 06 Feb 2020, 19:21

If the car is worth $500-600 bucks to you, pull the head and fix it. Fluids, head gasket, a new/used valve, machine work and new valve stem seals and lapped valves will have you back on the road, plus all the seals are easy to replace. It is not that bad a job if you do it yourself. The engine is darn good and with a new top end you should get another 100k from the transmission. My sister left hers at 250k-ish b/c the power steering rack was more than she could afford.

hoboken · Post by **hoboken** » 07 Feb 2020, 15:34

SuperHerman wrote: ↑06 Feb 2020, 19:21 If the car is worth $500-600 bucks to you, pull the head and fix it. Fluids, head gasket, a new/used valve, machine work and new valve stem seals and lapped valves will have you back on the road, plus all the seals are easy to replace. It is not that bad a job if you do it yourself. The engine is darn good and with a new top end you should get another 100k from the transmission. My sister left hers at 250k-ish b/c the power steering rack was more than she could afford.

it is, but i don't have a place to do the work. but the machining of the head would be expensive where i am.
That is y i asked about driving it 500 miles to where i grew up and work on it when ever i can. from my research i can get a engine from between 600 to 800 to

Post by **SuperHerman** » 07 Feb 2020, 19:23

Makes sense. Based on the other comments and suggestions it should make it. I suppose you could do a couple day test run first.

Engine swap not a bad idea, but removal is easy if one has a lift, not so without one. A head is pretty easy, but it requires more time. You should be able to pull the head in less than a day, and bring it with you to clean and prep plus lap the valves.

Theoretically you can pull the head, and if it is flat, just sand it correctly and skip the machine shop. Here I can get the head planed for $100 and that includes a cleaning - which is totally worth it. But, I have done heads, without warp issues, with a wet sand - not to get it flat, but to clean it up.

hoboken · Post by **hoboken** » 10 Feb 2020, 09:14

i am more concerned about the seat of the valve machining since valve it is chipped /cracked then worped

Post by **SuperHerman** » 10 Feb 2020, 16:25

A legitimate concern, unfortunately pulling the head is the only way to know. Prudence would say call around some machine shops and get a quote for replacing the valve seat then make the decision of new engine or head work.