4.6 L engine tap with exhaust smell

[Petesexpy]

the last few weeks I noticed an exhaust smell i the engine bay. Last friday (5 days ago) I noticed what sounded like a leaking exhaust, but very faint. I figured my driver's side manifold was leaking, so I waited a couple days with no worries. Finally, on the third day, my WIFE noted how bad the noise was and that told me something weird was happening. When I checked the engine that evening I realized that the noise was tapping coming from the center of the engine, heard the loudest from the bottom. Wife noted slight loss of power. If this is what I think it is, it means new engine (this one is around 250,000 MI). I just invested about $4K into this 2000 car, and additional $2K will bankrupt me. Any educated opinions (other than crankshaft, rod, or camshaft)? The sound is EXACTLY in the center of the engine and sounds exactly like a leaky exhaust. No clue why it smells like exhaust, since I do not seem to have any leaks. .

 

[Yager]

Drain your oil and look for metallic. id also cut apart the oil filter and check it. Is it erratic sounding tap or is it like a pattern that increases with rpm?

 

[Trainmaster]

From what you write, it could be anything from a bad injector or plug to a cracked exhaust manifold to a valve problem to a rod knock.

The fuel smell would indicate a miss or an exhaust leak.

I would check the cylinder balance with a computer and snoop around with a mechanics' stethoscope and then a compression test... Feel around under the manifold for blowing exhaust.

That's a virtuous life (250K miles) this engine has led. Could be anything at this stage.

 

[01ExpeditionXLT]

Check to make sure the plugs are seated normally. Maybe you can record a video and share it with us?

 

[Petesexpy]

Thanks, everyone. It turned out to be a cracked manifold. No idea how I could NOT diagnose it correctly, but I didn't. So all is good. Rad support replaced, rear subframe replaced, both manifolds replaced, new AC compressor, rear heater core replaced. The only thing remaining is the front heater core...

 

[Ulver]

Thanks, everyone. It turned out to be a cracked manifold. No idea how I could NOT diagnose it correctly, but I didn't. So all is good. Rad support replaced, rear subframe replaced, both manifolds replaced, new AC compressor, rear heater core replaced. The only thing remaining is the front heater core...

Good to hear man. That's some scary stuff. Was the crack visible?

 

[Petesexpy]

Good to hear man. That's some scary stuff. Was the crack visible?

Nope. No exhaust stain, no hot gasses leaking, NOTHING. I'm glad I have a fantastic mechanic 3 miles from my house...

 

[Ulver]

Nope. No exhaust stain, no hot gasses leaking, NOTHING. I'm glad I have a fantastic mechanic 3 miles from my house...

I have the same issue going on with my Mustang. Extreme loss of power, engine sounds like a diesel, smell and sound coming from manifold, bad gas mileage and it just doesn't want to go. Took the engine apart and valve springs, rods, etc look good.

 

[William1]

Newbie here. But I’ve owned my ‘01 Expedition for nearly 20 years. I’m only at 215Kmiles. But, I’ve kept it on the road by puttinga lot of work into it.

That said, common causes for what is described here could be a bad EVR valve, or tubing. A new EGR valve could make a world of difference, and thry’re not at all expensive. Maybe $50 at a local auto parts store.

Another posseibility, one I don’t hear a lot of people discussing in forums or anywhere else. But the carbon canister and the purge vent valve. Lastly, it would be good to check the vacuum sensor and the vacuum solenoid.

Hopefully, no one beats me up for this...