Engine Question

[gr_elvis]

Can a bad intake gasket on a 3.4 twin DOHC engine cause a valve to suddenly burn and what symptoms would I look for to confirm this?  

My cars idle had gone cazy btw 2500 and 3000 rpm s  but it was running great no miss or popping etc, so I took it to a local shop and they said that the intake gasket was bad causing the idle issue. They replaced the gasket and also changed the spark plugs but after that they said it wasn't running well so they took it back apart and said cylinder 4 has a burnt valve and the heads would need to be machined at a cost of about 3000.00 or the engine replaced. They want to charge me 917.00 for what they have done. Something doesn't sound right to me . They were supposed to troubleshoot the idle problem but didn't find the "valve" problem until they reassembled the engine. I asked wouldn't you have discovered that when you did a compression test in the process anyway and they told me no they wouldn't have done a compression test?. I think something is fishy. Anyone have any input for me? Please email me at gr_elvis@yahoo.com .  Thank you  

[White93z34]

How did they arrive at a burnt valve if they haven't done a compression test?

I mean I wouldn't do a compression test for a high idle issue. The symptoms you describe is textbook intake gasket problem on these, which they found and confirmed.

Did you authorize this disassembly and diagnosis... how far did they tear it down?

[gr_elvis]

They said they replaced the plugs and intake gasket but then it wasn't running well so they took it back apart and supposedly discovered the burnt valve they did not tell me how.

[55trucker]

Soooooooo.....at the moment.......what state is the car's engine in?

[bluecalais79]

This was exactly the issue with my 3.4, when it was cold the idle rpms RACED up and down, it was really ugly to hear, then when it got to normal temp it leveled off a bit but it only got worse and worse. And the car was getting about 7mpg around town. I had the intake manifold gaskets replaced and that did the trick. This was not a cheap job, but no way was I going to do it. I'm now back to 25mpg on the hwy and it's running smooth as silk at any rpm, any temp. 

Burned valve? Only one? It's not adding up. 

Edited September 10, 2021 by bluecalais79

[Jim_rockford_007]

Did they say they did a leakdown test ? did they send a camera down the intake port  and take a pic of the burnt valve, you need to make them show you the proof of how they came t this conclusion. When I was a tech, I would always try and show the customer how I came to a high priced repair. Think of it like being charged for a crime, Its not  your job to show you are innocent its their job to prove you are guilty, Make them show you the proof.