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burnt valve symptoms

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Old 04-07-2006, 10:52 AM   #1
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burnt valve symptoms

i made an appt to have my 4runner looked at on monday..... check engine light (code 26) is coming on and off from time to time.... in addition, it is running rough at idle (like a v8 hot rod).....

got off the phone with my mechanic and he thinks it might be a burnt valve..... o2 sensor was recently replaced and headgaskets were done 1.5 years ago.... hes a good friend of mine .... and recommends that if it is burnt valve, to not waste anymore money on it and get something else....

my questions are:
- what are the symptoms of a burnt valve?
- what's the fix? ........ cost?
- what recommendations do you all have, if it is a burnt valve, fix or sell?
i would love to get a new car, but i don't want a car payment(esp. when im trying to get into homebuying)

i value your guyes opinions so thanks.....

JQ
1993 4runner v6 4x4 auto
http://www.cardomain.com/ride/694142
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Old 04-07-2006, 11:11 AM   #2
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Running rough is not indicative of a burnt valve. I never do distance diagnosis. Don't even worry about what it could be without actually knowing what it is.

If you have to end up buying something else, why not another toyota?
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Old 04-07-2006, 11:20 AM   #3
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Depending on the cam overlap, occasionally a sign of a burned valve is intermittent suction at the tailpipe. With the engine overnite cool, you might try starting it and putting the palm of your hand over the exhaust pipe to see if you can feel some suction. The exhaust won't be too hot at that time and you may be able to feel it.

Another way is to hook a vacuum gauge to a port on the intake manifold and see if you get some fluctuation. Check here for more info:

http://autorepair.about.com/cs/troub.../aa112401a.htm

Mike in AR
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Old 04-08-2006, 06:52 AM   #4
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Do a compression test......... if you get an odd reading in a cylinder, put some tranny fluid in through your spark plug hole and put the compression tester back in , turn it over and get a new reading.......... should show compression thats a valve problem, and if it doenst , you got a dead piston and or rings .......... wait did i just explain that right cus i havent been to sleep since getting off graveyards shift this morning?
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Old 04-08-2006, 02:24 PM   #5
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Add oil to cylinder and retest compression.....

Reading changes/goes up = worn piston rings/cylinders

Reading stays the same (low) = burned valves or blown headgasket
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Old 04-10-2006, 05:46 AM   #6
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I have the same problem with the 92 I recently purchased, no compression on the #4 cylinder. I have already picked up new gaskets and headbolts and plan on opening up the engine next weekend. If the damage to the head is bad enough, I will just replace the head. A new one from ADC Cylinderheads is about $200 with no core charge. I purchased one from them last year for my 88 Supra and it is good quality.
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Old 12-14-2008, 08:46 AM   #7
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Ya, im happy that I stumbled across this forum because a mechanic told me that I had a burnt valve on my 22re, because it was running a bit rough, exhaust is kinda popping irregularly with a rather rich odor. Compression checks out at and even 150psi on all 4 cly. w/ no fluctuations after adding some oil in the cylinders. There are no vacuum fluctuations at the manifold nor are there any vacuum leaks, I just replaced both manifold gaskets to be sure of that. O2 sensor, plugs, wires and obvious stuff all replaced. timing at 5 or 6 degrees (short circuited.) Plugs are a nice light tan colour. No oil in coolant or vise versa indication a blown head gasket. Cam timing marks just slightly to the left of 12:00.
However, the engine runs best when the valves are adjusted slightly looser than what specs call for. What could that mean? But it's still rough, low power, hard on fuel.
So Im really stumped here. Should I pull the head and look at those valves? What does a burnt valve look like? Can you re-grind a burnt valve?

Last edited by kevin g; 12-14-2008 at 08:49 AM.
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Old 09-04-2009, 11:26 AM   #8
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Any news Kevin? I have the same problem. Also have cheked/chagned almost everything...
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