Exhaust leak +

[2000flair]

Hi there. About 6 weeks ago my rv engine became very loud so i brought it to the garage. They said 3 pins on the left manifold were missing so i had a leak.
I had to wait until last week to have it fixed because the shop was fully booked. They said i could drive it like that for a while without a problem other than the noise and the slight smell of gas that sometimes came in.
They replaced both manifolds and the sparkplugs cables which they said were damaged from the heat and after $3800, i drove away on my now very quiet and pleasant rig. An hour later they called me saying they forgot to install a metal protection piece and that i could just swing by on our way to our camping trip last Friday.

They installed it and we took off. A few minutes after taking the highway, the engine ride became a little rough.

The road had some hills and as we went up, the rv became less rsponsive and had a very hard time climbing and at this point it was as loud as before the fix.
I opened the dog house and noticed the EGR sensor was disconnected. I started the engine and put my hand close ro the spark plugs and could feel air coming out. I also went under the rv to check for missing pins but didn’t see any.

I did notice one of the spark plug cables seemed damaged, like it had little cuts.
On the way back, the engine was loud and unresponsive but we made it home.

I Immediately drove it back to the garage and on the way, the engine cut off completely twice while driving. Both times i started it back with no trouble, but still…

I would like to know if anyone has had something like this happen to them and also if i should be particularly worried that the shop may not be doing a good job. I’m worried that they will try to put the blame on me and try to charge me again for fixing a problem they didn’t really solve the first time around. I also noticed that the gas consumption almost doubled.

Sorry for the long post. I tried to give as many details as possible.
Thanks

[jimh406]

You mentioned it looked like some spark plug wire damage. My guess is that.

[2000flair]

I spoke with someone at the shop and she said maybe the manifold was defective, they’re getting a replacement and they’re checking things put. Hopefully it’s just a bad part.
I’m still curious, is the leak issue the reason the rv struggled like it did and ran so erratically on top of smelling like gas and consumed so much more than usual?

[rjstractor]

enblethen wrote:
That is strange for a 7.4 GM engine.

IIRC cracked manifolds and broken bolts and studs were fairly common on both the GM and Ford big block V8s. I wasn't thinking V10, although they have had issues with manifolds and spark plugs blowing out, they are a coil over plug design with no real spark plug wires.

[jimh406]

I’ve had shops make mistakes before. I guess you’ll learn if they are trustworthy based on how they respond to additional fixes.

[Grit_dog]

And there’s nothing with the EGR, exhaust or a misfire due to bad spark plug wire that would cause it to smell like gas. If you meant gasoline and not exhaust gas.

But it really sounds like it might just be misfiring on a cylinder maybe 2 and a spark plug wire may have been damaged or 2 wires reversed when they presumably reinstalled a heat shield.
It runs so it’s 99% not fuel pump. Generally they are fine or dead.
And it ran fine for a couple hours after the initial repair.
I’ll take spark plug wires for $200 Alex.

Do this. Start it note how it’s running. Shut it off and pull off a suspect spark plug wire and restart. If it’s worse, that one ain’t the problem. Repeat until you find one that doesn’t change how the engine runs when you remove it.
And if it’s none of them then there’s a different issue.

[enblethen]

That is strange for a 7.4 GM engine.

[2000flair]

enblethen wrote:
Must be a Ford V-10!
There is more expensive problems! Possibly new heads!

It's actually a Workhorse 7.4L V8. Sorry, I should have mentioned that.

[Grit_dog]

enblethen wrote:
Must be a Ford V-10!
There is more expensive problems! Possibly new heads!

Can’t be a V10 if it has spark plug “cables.”
But I do truly feel for the OP and others like them who don’t know much about what are generally the most expensive possessions we all own, vehicles and houses.
Good luck and maybe give us some more clues to help ya figure it out.

[Grit_dog]

I don’t know where to start, could write a book with suggestions however seems like you have issues either with exhaust leaks, mis-firing or potentially spit a spark plug.
You did get ripped off by the first shop the first time. That’s a fact unless they did more than put new exh manifolds and spark plug wires. Even if they had to extract a few broken “pins” (exhaust manifold studs or bolts).
Also at least tell us what engine we are trying to guess what’s wrong with…..

[enblethen]

Must be a Ford V-10!
There is more expensive problems! Possibly new heads!