Burnt Exhaust Valves. Ideas?

Nope....certainly not the plugs that were in there, or are currently in there.

The Haynes manual says nothing about a dual ground plug. If this were the issue wouldn't there be problems with every cylinder?

 

I just looked it up and you are correct. The part number provided in the Haynes is a Dual Ground plug.

Geeez.

So do you think this could be the whole problem with the misfire in the #6 Cylinder?

 

That tells me alot right there. jumped time causing a misfire, might be masking other cylinders that retarded or advanced,,ever so sightly.

A simple compression check will show a dead hole, so long as he does at least 2 other cylinders to compare.

Done properly, a leakdown test is ideal, you'll hear alot of air hissing back thru the intake if it is a burnt valve, plus it give you a better overall understanding of the health of the cylinder.

Get a second opinion, but dont let on that it was coded for a misfire on #6. Tell him about the parts replaced and let him diagnose,,see what he comes up with.

The problem with educated guesses is that it ends up costing you money that you really didn't want or need to spend. There educated guess doesent get you your money back if they are wrong. Not being condescending there,,just saying.

Might be just the wrong plugs. At this point, any cheap try is worth a spendy one.

 

That sounds like the plan! I appreciate all the feedback.

I'll post the progress or lack there of.

 

That's good news. I had no clue what something like that should or could run. I figured the dealer might be out the roof on pricing but the upside is that thay have Toyota certified mechs...

 

Sounds good Josh,,good luck.

,,And thank you for your military service.

FWIW, Haynes softback manuals page skip all around the crucial info sometimes and are generally confusing. Thick Toyota manuals for the in-depth stuff with excellent diagraming and page indexing. spendy,,but worth every penny.

 

Thanks for the link to the manual...and the rest of the information on troubleshooting. I have noticed that the Haynes does skip around a lot, very confusing. I seriously think Naval aviation maintenance publications are easier to read than that Haynes sometimes.

Again, I appreciate all of the feedback. I'll tune back in tomorrow to update you guys on the plug switch. I got that leak down/compression check scheduled for 7:30 a.m. tomorrow as well.

Thanks again!

 

Poor mans leak down test.

It does not take a great volume or pressure to test for a seal just remember listen for the leaking air.

Bring Suspect cyinder to top dead center (in this case #6) on the conpression stroke. For older distributor igniton trucks you can point the rotor to fire the cylinder you are working on to get you close to TDC.

With spark plug out put any continous compressed air into the spark plug hole. Maybe a combinatin of a rubber hose (stolen) from the air box breather or radiator over flow and blow gun from any small compressor or what ever red-neck way you can find to blow in the hole. A burnt exhaust valve has a direct bleed thru to the exhaust. So you listen at the tail pipe. You will hear the hiss of compressed air if the valve is bad. If you find a bad seal you will be amazed at how loud and clear the hiss of escaping air is.

If you pressureize the cylinder with a thead in test fitting it will try to turn the engine over (before warned). Some hold the front crank bolt with a braker bar or ratchet, others vice grip the flywheel at the bell housing, some try low range 1st gear with the p-brake locked down.

I have an air line made up for cylinder leak down testing and use it with a regulator at 40 psi. Similar lines can be found on compresion testing tools (Sears / Ebay) with the quick release line. OR You can make one up with an old spark plug (drill out the center) and assemble your own compression testing line with assorted bits form the hardware store.


Tail Pile = Exhaust valve
Air Intake = intake valve
Oil fill cap / crank case = piston or rings


PS: You are 80 miles south east of me ~ the Yota fraternity is strong down that way. The further you get form the NAVY base the better your chances are at finding a reasonable mechanic. I've got good friend who does Suzuki Samurais in Chesapeake (he knows where the local Yota crowd is) / a good resaonable mechainc in White Stone .75 hr north / and a friend who used to run with the Grave Digger bunch and build older Yotas just down at the VA NC line. Either of these guys can steer you in the right direction if you need further help. Also Try Va4x4.com and Tidewater 4wheelers. The Tidewater 4-wheelers are a senior 4wd club that has been around long before the internet. Those guys could definatly get you the help you need at a fair price. If you would like any contact info just let me know.

Michael

 

I hope the spark plug change helps if you are still concerned about excessive carbon build up you may want to try a product called Techron, some guys like to pour Sea Foam in the intake thats your call.

http://www.techron.com/docs/Chevron_Techron.pdf

 

Whitfield -I dropped the truck off this morning for the compression / leak down test...prior to reading your post. I'll refer to those tips if I ever have to go through this again though. As for the local Toyota scene, my truck is 2WD, so I'm not equipped to have any serious fun out here. When I was stationed in San Diego years ago, I enjoyed my truck a lot more out in the Anza Borrego Desert and Ocotillio Wells. FWIW, since you are not too far away....I found a "Toyota Only" junkyard out in Ivor a while back it's on Hwy 460.

Plug Change -

It reduced some of the "shake" when idling in gear and it starts up a lot quicker. However, it still shakes pretty bad and needs something. I'm thinking more and more it's just a timing issue. But the results from the leak downand compression test will tell all.

The old plugs -

Had only been in for 3 weeks and the electrode on every plug had a large "V" groove eaten out of the center.

 

They sell a V-Groove plug so that's prob. what you had installed. I'm following this too, w/ my bet being against a burnt valve. UNLESS it did jump a tooth on timing and make a "hot spot" fopr the valve to burn easier. Usually, these days when a valve burns (and most times I've seen it's the valve that burns, not the seat) it's from a preexisting condition that insurance refuses to cover.....wait, that's just medical....never mind.

 

Compression Check Results:

#1 DRY 150 - WET 180
#2 DRY 150 - WET 200
#3 DRY 150 - WET 180
#4 DRY 145 - WET 200
#5 DRY 160 - WET 180
#6 DRY 050 - WET 065

So, the pressure on Cyl. 6 is signifigantly lower. I'm guessing this assures a "Burned" or damaged valve? Whatever the case may be, I'm taking it in to the local dealer tomorrow to have the timing belt replaced. The Quote for the timing job was $340 including parts. Believe it or not they quoted $750 for the valve job w/ parts.... I can only afford the timing this month but I'll get the valves done before February for sure.

Question:

My truck idles around 750 RPM in park and drops to around 500 in gear. At 750 the shake from the engine problem is not that bad but once it drops....it's an attention getter for sure. Is 500 RPM normal while in gear?

 

No sir. I would have noticed the groove when I was gapping them. That was burned in there from spark, without a doubt!