yummybrains

Extreme newb here, so please be gentle. 97 4Runner Limited, 3.4 liter v6, 4x4, 250,000 miles. So, it started running rough about two days ago then the CEL came on. I drove it to a local shop and was told I had low compression in cylinder #6. Everything else checked out great. They said I needed a valve job, but as they were pulling it out of the garage it started running smooth again, like usual. They said the valve must've cleared itself and sent me on my way. Then on the way to work later that day it started running rough and the the CEL came on again. I drove it again this morning and it ran great for about 2 miles then the CEL, ect... again. I agree that it probably has carbon built up on the valve(s), but wanted some advise as to how I should proceed. I LOVE my 4Runner and was hoping to drive it for at least another 50,000 miles. it runs great otherwise and doesn't have any oil leaks or other issues. I'm no mechanic and can't really justify sinking a pile of $$$ into a car this old. My main questions are; is there anything else I can try before committing to the valve job, and how much should I expect the valve job to cost? I'm in Hendersonville, Tennessee if that makes any difference. I did not get an estimate from the shop. I did do some research on this list, but am extremely short on time, so I thought I'd go ahead and just ask.

Many thanks,

YB

Tdanger87

There are a few good threads on here about the use of Sea Foam with the problem your having. I would try and link them but I'm on a phone, so I guess you will have to search.

Good luck though!!!

yummybrains

^Excellent! Thank you.

kball

The only valve problem that's going to cause low compression is a burned valve and they don't just get better intermittently. You either have a flaky coil or injector I think. I wouldn't go back to that shop.

hotlavaaaa

It might help if you could share what codes it was throwing.

yummybrains

I saw the codes, but don't remember what they were. It was showing a misfire on #6.

Yesterday I did the Seafoam/water treatment as a last resort before either fixing her or buying a new (used) engine or 4Runner. There was no change (except that the problem seemed to get significantly worse) until the final Seafoam part when it finally blew out whatever was obstructing the valve. She now seems to be running better than she has in years. I drove her about 30 miles to work this morning averaging 80mph and she was raring to go, with a noticeable improvement in acceleration. I'm going to do that treatment again next weekend and then get her tuned up and detailed.

It's difficult to describe the amount of carbon that blew out of the exhaust. I literally smoked-out the entire neighborhood and left a big wet black patch of crap on my driveway.

I gotta say, you guys are awesome and thanks for the help. I might never have found the Seafoam thing were it not for this list and probably saved my newb a$$ $1,500 or so. I'd buy y'all a beer if it was possible. Thanks again Tdanger for the tip and Texas_Ace for the write-up!

Best,

YB

yummybrains

You might be right and the Seafoam treatment might be a temporary fix too, but for now I'm just happy she's running good again. If it happens again at least I'll be more prepared and know what the problem is. I've used that shop before and have been happy with the service, but I probably won't be going back. It's very hard to find a good, trustworthy shop, especially when you don't have a clue.

Best,

YB

yummybrains

It was a bad injector.

Thought I had it fixed with the Seafoam treatment, but it (cylinder #6) started misfiring again a few days later. She's running great now and I found a good mechanic!

icerunner

Your duel electrode spark plugs are only good for 30K miles.. you will get a misfire IF your plugs are due for changing..Seafoam will only foul the aged plugs out WORSE...Likely due for a plug change, and ONLY use DENSOS..
Icerunner over and out.