We just got a 92 6 cyl. pickup with about 260K miles. It was a gift from a family member. It's been idling a bit rough. New Denso plugs and Toyota wireset helped a lot (gap was way off on the old plugs), but it won't pass emissions.

The mechanic I took it to for the emissions test did a compression check and it's looking like it has a burnt valve. Compression in #3 is about 50 PSI, so we're going to have to tear this thing down.

I noticed that a few places on the Internet advertise rebuilt heads, ready to install, for about $200-$300 per side. Anyone have a good experience with rebuilt heads from a particular source?

With so many miles on the clock, I'm a little reluctant to do the top end without reworking the bottom end, but money's tight right now and I don't want to do more than I have to to get this thing back on the road. Would anyone do just the top end on such a "mature" motor, or am I totally nuts to even consider this?

I would drop the pan and pull the rod and main bearing caps to take a peek at the bearings. Also check the cylinder walls to see how much of a ridge ring there is, that will tell you the condition of the cylinders.

What was the compression of the other cylinders? If they are w/in the Good zone and no rod knock on start up you should be fine for awhile w/o a bottom end rebuild.

Is he positive it is a burnt valve or do the valves need to be shimmed? Shimming the valves should run you about $400 so you might consider that as a starting place. If the #3 exhaust valve is bad it wont cost you anymore start w/a valve shim because you have to remove all the intake/etc anyways.

You should be able to have a local machine shop check/rebuild the heads for the same price or less, call your local Toyota dealer(or closest one to you) and see who they use. The shop I used rebuilt my heads for about $500, which included new headbolts and a valve shim.

Make sure your mechanic knows he CAN NOT reuse the current headbolts, they are Torque-To-Yield(TT-Y) headbolts and are a one time use only headbolt. Reusing the TT-Y headbolts will guarantee a head gasket failure. You also have to use a new knock sensor and knock sensor wire, if you don't within a month of the rebuild your check engine light will come on and the code will be for a faulty Knock Sensor.

If you have the extra money I would also recommend sending out the injectors to be cleaned/rebuilt. There are some posts on here with links to injector rebuilders, if you don't have a local shop that can do it. Injector rebuild run anywhere from $7 for cleaning to $32 for a cleaned/rebuilt and balanced.

Thanks for the replies. The other cylinders were all within the acceptable range, and there's definitely no rod knock. The engine sounds great, starts right up, and pulls strongly, especially on the top end. It's just had this lopey idle that won't clear up with a tune up and is a little sluggish and misses a bit when accelerating from a dead start. It also has high HC readings at idle, which is why it wouldn't pass emissions. HC readings at 2,500 RPMs are good.

I'll pull the pan to examine the bearings. There's a good machine shop close by that says they will rebuild the heads for about $500. The mechanic thinks it's a burnt valve, but we didn't discuss shimming as a possibility. I also wasn't aware of the knock sensor issue. Thanks for the heads up on that.

Yes, a lot of people don't know about the KS and wire, even a lot of professional mechanics, the same goes for the TT-Y headbolts, unless they have rebuilt a 3.0 and have had to do tear into it again to fix the problem.

$500 isn't bad, paying a little more for local work is sometimes worth it, i.e, you have a local shop to deal with face-to-face, and not some faceless person on a phone.