ToyYoda

So I went to get my inspection done today (got a ticket for it being expired since sept.) I had to replace the catalytic converter with a magnaflow high flow cat. which didn't hurt performance at all and my truck smells a lot better and passes inspection. Anyway..after it was all done, I passed but the guy told me the truck had a burnt exhaust valve or "dead cylinder". Normally I would say whatev... you're not stealing my money BUT my idle has been really rough unless I idle it up but then it will surge. I barely passed low speed emissions. 220 standard and I got a 218. I replaced the idle air control valve at the same time as the cylinder head and have always had the problem. Could it just be the IACV or whatever it's called?

My question is, could it be a burnt valve? My cylinder head is brand new. What are some symptoms of that problem and how can I test or fix the problem? Or what do you guys think the problem is?

NicCantDecide

if you suspect a burnt valve or bad rings the way to check is pretty simple.

First do a compression check on each cylinder and write down all the numbers. If one of them is significantly lower than the others then you have a problem in that cylinder.

If you do have a problem with certain cylinders, the next thing to do is do a compression check again on those cylinders, but this time spray some oil onto the top of the piston beforehand. What this does is tell you if the problem is with the valves or the piston rings (the oil covers the piston rings and seals them partially). If your compression goes up, its your piston rings, if it stays the same its with your valves.

The next test you should do is a leakdown test, this will tell you how much air is leaking out of the combustion chamber and which side its leaking from (intake or exhaust). No engine is perfect, but I dunno the allowable percentage on toyota heads.

If you have leak a little higher than normal its usually just caused by carbon buildup. If you have a lot of leak, say over 40%, its probably a bent or burnt valve. In that case you have to pull the head and replace the valve (and while you're at it inspect the others too).

I may have missed something, I wrote this up quickly. i'm sure others will elaborate if I have.

thook

Is this a 22re? I don't remember.

In any case, a burnt valve could cause the rough idle and a dead cylinder, but so could a malfunctioning injector, dead plug, wire, or distributor terminal. Not a bad IACV, though.

I'm real skeptical a new head that would normally include properly adjusted valves would develop a burnt one. How did he determine you had a dead cylinder and also a burnt valve, anway?

(Edit...the control valve would give a bad idle, just not dead cylinder. And, what they've said....compression and leak down test.)

dcg9381

That guy is guessing.. probably guessing incorrectly.
Do a compression test if you want to know.

NicCantDecide

While it could be a bad injector/plug/wire/dizzy terminal, that requires dismantling the engine to some extent (at least the injector and dizzy terminal). A compression and leakdown test involves removing a spark plug and screwing a gauge in.

compression and leakdown should be your first step, if it gives no conclusive results, then move to your ignition system and fuel system.

dcg9381

I should note that I'm running a magnaflow cat also - 2.5" high flow..barely.. I mean barely squeek by on emissions.

thook

I'm aware of that, but I was only explaining that a burnt valve is not the only cause for a dead cylinder.....IF he has one. Besides, he's pulling the plugs to run the compression test....right? So, stick the plug back in the cable and see if it sparks. It's pretty easy.

The injector, of course, is a different story. Last resort test, eh?

NicCantDecide

And touch the spark plug to a ground also, my friend fried his dizzy because he didn't ground the plug before testing for spark.

And the injectors: yeah, pain in the butt to get to. I had a leaking o-ring in my sixth cylinder, practically under the windshield. I just took it to the dealership to get it fixed because I didn't want to deal with disassembling the intake manifold and fuel rail.

ToyYoda

The short block was replaced in 01' and the cylinder head in 07' so most of the parts involved with this dead cylinder are fairly or very new. I'll do a compression test and post up the results.

What's required to do a leak down test?

NicCantDecide

Doing a leakdown test is really easy, all you need is a leakdown tester and an air compressor.

Search leak down test on google:
http://www.geocities.com/dsmgrrrl/FAQs/leakdown.htm

Its fairly straight forward. There's also a guide to building your own leakdown tester on google. Good luck.

CyMoN

a expensive tool well only around 45$ to 75$ online on ebay

have you checked your valve adjustments?

NicCantDecide

Its pretty unlikely that it would be a valve adjustment. The compression and leakdown test are the easiest and fastest to do (and most likely to show results) so it's probably better to do those tests first.

When I rebuilt my honda engine I forgot to do a valve adjustment because I was in such a rush (bad idea) and the car would barely start, I'd have to gas it to get it past cranking. I realized 10 minutes later I hadn't done valve adjustments. That's a very extreme case though. I doubt the valve lash has gotten so far out of tune to have a rough idle in less than a year of having the new head installed.

ToyYoda

You're right about that. I've tried adjusting the rockers like the manual says and adjusted them by hand my way and I still get the same idle. It actually sounds pretty cool with it's idle issue...like I have some crazy huge cam.

machabees

I understand that sound fully. And I know that big lopy cams will obviously make an idle rough there seems to be no way around it. But vehicles like that still sound broken to me. My buddy put a cam in his volvo sedan and the thing has balls now but it still sounds like crap at idle to me.