So my mechanic did the compression test on my car and said cylinder 4 was showing 30, meaning there was no compression in the cylinder and hence the misfire

He believes the problem is the valve and not the piston rings and said its a $2,500 fix but recommended against it since my car has 130K miles on it

What you do guys suggest I should do? Any other fix available? Is there anything I can test?

A new engine?

Drive till the car dies?... but unfortunately it is giving me freaking 14-15mpg right now and I don't think I can afford to drive a guzzler like that.

Thanks in advance for any input(s)!!

 

I believe the FSM suggests pouring a little oil in the cylinder then doing the compression test again. If compression significantly increases with the oil then you have piston/ring problems, if it stays the same you have a valve issue. I would try that first.

If you need the exact info let me know and ill try to dig it up.

Goodluck!
-Rob

 

The mechanic thinks its the valve so I have no other option but to believe him. I don't own a compression test meter so can't do it on my own. Assuming he is correct, what do you suggest I should do?

Does $2,500 sound reasonable? Or should I just look for a new engine and drive the car as little as possible? Or sell it for whatever I can get?

Thanks!

 

If it were me and i was 100% it was valve related, I would look around for a used head, they aren't *that* hard to come by, just replace the entire head since actually fixing the one you have would likely cost more in labor. Its still a pretty big job but it can be done in the car in about a day.

Labor wise i would say around 12hours for an experienced VQ mechanic + whatever you can get the parts for. I really think you can find a used head if your patient, just make sure its within specs for levelness.

Goodluck! Let me know if I can help you with anything!
-Rob

 

Thanks for the info! What is the technical term for this part? Is it simply called the 'head'?

Also what do you think would be a better route? Buy a used engine, replace the head, or replace the valve on the cylinder?

One last thing, can I damage anything else besides the already damaged engine if I continue to drive the car? Or should I try to fix (whichever route I choose) ASAP?

 

If the valve is stuck open, causing a constant misfire I would not continue to drive the car. This condition could cause cylinder wash and kill your bearings (among other issues).

Yes its just called a Cylinder head. I wouldn't suggest trying to repair the valve in the current head because 1) it would likely cost more overall since it would take much longer and 2) I wouldn't trust just any mechanic to do such a job.

You could also buy a used engine, and it probably wouldn't cost much more overall than replacing the head, but with tons of VQs out there with spun bearings and/or oil consumption its kinda risky. It would be hard to know that your getting a good reliable one, that's why i say if your bottom end is fine, just replace the head, that way at least you know what you have.

-Rob

 

[QUOTE=onevoice;6205337]So my mechanic did the compression test on my car and said cylinder 4 was showing 30, meaning there was no compression in the cylinder and hence the misfire

it could be a BENT valve stem, could be broken compression ring( top slot), could be blown head gasket...BUT it could be just a small chunk of carbon stuck on valve lip....try a can of Rislone for about 60 miles...drive slow and let this stuff work in.. cost u about 3 bucks, worked for me in the past..try it u might be surprised...write back and let us know.

 

[quote=slim17265;6207196]Rislone fuel injector can? I simply pour it in when I fill up the car, right?

EDIT: I also found Rislone compression repair, Rislone ring seal and Rislone engine treatment. I am assuming you are talking about the compression repair one?

 

Seems rather pricey. I wouldn't bother fixing your high mileage motor. Find a lower mileage engine and swap it in. Might cost more but it will last way longer and add a little value to the car.

 

[quote=onevoice;6208009]I believe you want engine treatment it is basically 90% kerosene and 10 Xyline. nothing cuts carbon quicker...try it.

 

Going way back here (holy thread revival), but I am having the same problem, waiting to take my engine apart this weekend. What ended up happening with yours? I pretty much have the same exact problem, just different cylinder.

 

What the hell is it with these cars and cylinder #4. I lost ALL compression in cylinder #4 with less than 120Kmiles on my '04, turns out the engine ate a big chunk of the exhaust valve on cylinder #4.

I did the work myself with my brother, but I fixed mine.

Here's the thread : https://g35driver.com/forums/g35-sed...back-road.html

Good luck, keep us posted please.

DBarnes