Bad or wrong Spark plug cause hissing sound
 

I just got my car diagnosed by Chuck at COW (they are great by the way) for a hissing sound from engine bay and I was just told it was due to a bad spark plug or wrong spark plugs.

When I hear hissing the first thing I look for is vacuum lines that are loose, cracked, or completely off. Then I look for any looseness in the intake, exhaust leaks, and try to go from there.
Maybe the wrong spark plug wont sit properly in the head so there is air moving in and out???:cheers:

Oh, idk, I just spoke to mechanics and he sad that was the problem.

unfortunately I did have the sound you described. it was a cross threaded spark plug.

:eek:

When you say cross threaded do you mean that the plug was not properly installed?

The person did install new Splitfire spark plugs.

If the plugs are cross threaded, then they would not be properly installed.

If the plug is not "sealed" with the head, combustion pressure can escape creating a "hissing" sound.
Your engine is just a large air pump.
Leaks on the intake side will be sucking air into the system, and leaks on the exhaust side will be pushing air out of the system.
A spark plug not properly sealed will have both of these effects (depending on what cycle the piston is on).

My O2 sensor was causing my hiss or fphtttt...fphtttt.sound .I swear I thought I had a bad rocker arm.Just so you know...

I see what your saying. It is amazing that the guy who put the plugs in had no idea what was wrong, he even changed one of the exhaust manifold gaskets. I had to being it to Chuck at COW. They are great people. Thanks for your info. :cheers:

Yea that is how mine sounded. Well COW diagnosed it to be the spark plug, he says it runs 10 time better. Let see... Thank you...

no it was not properly installed by a gm tech(who did not use anti-seize).
short story is that i ended up replacing the head.

Here's the deal.....
 

Here's the deal.....


You have an aluminum headed C4 engine. They use LONG REACH GASKETED plugs.

The dick you took your car to the last time for it's spark plugs cross threaded the #2 spark plug hole trying to put a SHORT REACH, NON GASKETED (taper seat) PLUG into a car that dosen't use one.

You're lucky the head didn't have to come off.

For anyone that has worked on a C4 with the stock exhaust manifolds and air pump check valve and plumbing on the passenger side between (angled) plugs #2 and #4 KNOWS FULL WELL that it takes divine intervention to get that spark plug threaded correctly and snugged down with all that emissions crap in the way.

Be thankful that he didn't do any more damage than he did.:thumbs:

It seems to be running much better from what I see, but I'll take it for a ride tomorrow and evaluate it more.

I haven't seen this car for a year or so, I wanna look it over carefully.

BTW...That new paint job sure does look nice!
Chuck CoW

Ohhh ok Chuck sounds awesome. That is why I am only bringing my car to you. You sure do know what your doing, hands down, unlike some of these other mechanics out there. Thanks again.

At least the paint job came out nice. Btw nice video.

Yea I know right. It is amazing how important it is to find a mechanic that mostly works on Corvettes. He is a straight shooter too. He tells you how it is and will end up. Well I hope the travel time to your mechanic is well worth it as well. :cheers:

Oh ok lucky you then. I wish I had the time, skill and place to do my own work. Not only do you save money but it can be fun to do as well as rewarding. Living in the city I can not do anything myself.

GJ Chuck :thumbs:

Yea man god bless COW.....

Found that coolant leak.......
 

Found that coolant leak.......on the test ride....That you forgot to tell me about....:toetap:

We're diggin' in right now.

More on this later today.

Chuck CoW