Burnt #3 cyl exhaut valves about 30K ago. I replaced the valves (just lapped them) and now it has done it again 30K later. I'm replacing the head with a remanufactored one along with new fuel injectors. The injector for that cylinder is the only thing that I can think that would cause it? Any ideas guys? It does use about a quart of oil every 1K miles. EDIT-the valves were always adjusted properly.
2000 Honda Accord 4cyl burning exhaust valves
- Thread starter TurboTravis
- Start date
I replaced #4 exhaust valves at about 100K miles on DIL's '99 CRV. It was easy to diagnose with a compression gauge. Valve seat recession causes valve lash to tighten up and that burns the valve. Evidently, Honda dropped specs for valve seats about '99. IIRC, I chucked the valve stems into a 3/8 drill and slathered the seat/valve area with valve grind compound. Anyway, put the valves back in, set the head upside down and level and filled chamber with gas. It wasn't perfect, but I set the exhaust valves a tad loose.and the engine was fine when he drove it into the junkyard with 170kmiles on it after it was totalled.
Getting a bit of oil? How many miles total? Lets see all the chambers.
What brand valves? OEM Honda or Chinese knock-offs?
Is that a missing chunk from the valve
Classic burned valve. They present as missing a chunk or as a crack. Either "look" is a simple burned valve.
The way to prevent this is to cut the seat angle correctly with a 0.060 width, install a new quality valve, and valve spring/or shim to proper tension, and ensure adequate tappet clearance. A new valve is probably already ground with accuracy. As the OP notes, lapping for a perfect fit can help. But is not the solution on an old seat that likely has too much surface area.
Unfortunately, on engines that consume oil, there is always the issue of contamination preventing adequate valve to head heat transfer, and recurring problems. A little more spring tension can help here.
Running lean doesn't burn valves. Running lean under heavy load burns valves.
If they're all burned it's not the injectors.
Loong time ago I had a bad coolant sensor burn valves on an engine. It was running lean all the time.
On my 454 suburban I tuned the carb to run lean at idle and lean at light throttle, the secondary jets were fuel dumps anything more than about half throttle and the secondaries would start opening and dump fuel into the engine.
I ran it like that for a year, at least 8,000 miles, no hint of burning on any of the valves when I pulled the heads.
If they're all burned it's not the injectors.
Loong time ago I had a bad coolant sensor burn valves on an engine. It was running lean all the time.
On my 454 suburban I tuned the carb to run lean at idle and lean at light throttle, the secondary jets were fuel dumps anything more than about half throttle and the secondaries would start opening and dump fuel into the engine.
I ran it like that for a year, at least 8,000 miles, no hint of burning on any of the valves when I pulled the heads.
TT, you've got more to worry about than just burnt valves. Look at your photo. Your engine is puking oil through the combustion chamber. How many miles and how is your vehicle used?
Was there engine ping or knocking (read: lean mixture or localized hot spots in combustion chamber)? Weak valve springs can cause burnt valves.
Curious: What do the other combustion chambers look like? Can you post images?
Since you're replacing the head with a reman unit, I wouldn't worry too much about the valve train.
Might be wise to just go ahead and replace (or service) the four fuel injectors
Thanks for the input. I replaced the head with a reman unit. Set the lash to .014, spec is .010-.012. Also installed serviced injectors.
A loose guide will cause one to burn too.
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