2004 8.1L Ticking/Rattle @1800RPM

[goborgoh]

So my 8.1 has 130K, no mods. I'm the third owner, was sold to me out of Canada. Some good amount of rust on the undercarriage but nothing to alarming.

 

Recently I hear a loud Ticking/Rattle right at 1800RPM that will continue if I hold it there. I'm assuming it's on of two things, lose heat shield or exhaust leak. I'm also getting a noticeable ticking sound when I accelerate and let off.

 

I have also lost 2mpg. Rough idle as well. No codes. I'm going to put it up in the air this weekend to have a look but I'm here to ask for guidance as well. Thanks in advance.

 

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[davester]

If it's the exhaust, that could cause your mileage problem, as it winds up sucking clean air into the exhaust, and then the O2 sensors make the ECM think the engine is running too lean, so it dumps more fuel in...this happened to me with my 6.0l, which had a number of broken off exhaust manifold bolts.

[goborgoh]

If it's the exhaust, that could cause your mileage problem, as it winds up sucking clean air into the exhaust, and then the O2 sensors make the ECM think the engine is running too lean, so it dumps more fuel in...this happened to me with my 6.0l, which had a number of broken off exhaust manifold bolts.

Would this cause my negative Fuel Trim numbers? I thought if it was seeing a lean condition it would be positive number? Thanks for your feedback.

 

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[davester]

I don't recall how the fuel trim numbers go, but you did mention that your mpg was down, which would point more towards it being too rich.

[RestorationRides]

The rattling could be coming from a baffle that has come loose inside of the muffler. If a baffle were to restrict the exhaust, then you would have a decrease in performance and fuel efficiency. The observations of substantial rust under the vehicle and known past operation in wet and cold environment (read Canada) would correlate well. Especially if this vehicle was used for short trips in such cold wet conditions, where moisture in the muffler would tend to accumulate and combine with combustion gases to form strong acids that attack the metal in the exhaust system...

 

Regards,

Restoration Rides

 

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[goborgoh]

The rattling could be coming from a baffle that has come loose inside of the muffler. If a baffle were to restrict the exhaust, then you would have a decrease in performance and fuel efficiency. The observations of substantial rust under the vehicle and known past operation in wet and cold environment (read Canada) would correlate well. Especially if this vehicle was used for short trips in such cold wet conditions, where moisture in the muffler would tend to accumulate and combine with combustion gases to form strong acids that attack the metal in the exhaust system...

 

Regards,

Restoration Rides

 

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How would I check for this(these) baffle to see if it's come loose? I appreciate your feedback. Cheers

 

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The rattling could be coming from a baffle that has come loose inside of the muffler. If a baffle were to restrict the exhaust, then you would have a decrease in performance and fuel efficiency. The observations of substantial rust under the vehicle and known past operation in wet and cold environment (read Canada) would correlate well. Especially if this vehicle was used for short trips in such cold wet conditions, where moisture in the muffler would tend to accumulate and combine with combustion gases to form strong acids that attack the metal in the exhaust system...

 

Regards,

Restoration Rides

 

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How would I check for this(these) baffle to see if it's come loose? I appreciate your feedback. Cheers

 

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[Raptordude]

I'd first look to see if the exhaust manifold bolts are broken off. Common problem on these. If they're ok, check over the whole exhaust for holes, any air getting in before the upstream o2 sensors will screw things up

 

Are the fuel trims messed up on both banks or just one?

 

Negative fuel trim means less fuel is being injected to compensate for a rich condition. Positive fuel trim means more fuel being injected to compensate for a lean condition. Your upstream o2 sensors are what control these readings

 

 

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[RestorationRides]

How would I check for this(these) baffle to see if it's come loose? I appreciate your feedback. Cheers 
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So sorry! I've been away for awhile. Let me try to address this question now with the idea that maybe you have not figured out how to check it through other means...

The best way to check for a loose baffle in the muffler without taking it off the vehicle is to smack it from underneath with something that won't dent it. Soft toed shoes such as tennis shoes can be helpful because they have enough Mass with your foot and your leg behind it but it's soft enough at the toe so as not to damage the muffler. By thumping the muffler in a rhythmic pattern you can really get that muffler bouncing up and down against its elastic mounting straps. If a baffle is completely loose you should be able to hear it bouncing off the bottom of the muffler can or wherever in the muffler it has fallen to. For smaller baffles that you might not be able to hear, or baffles that are starting to come loose but are still attached in some way, you can try a dead soft mallet rapping it against the edges of the muffler and work your way around that muffler listening for loose metallic sounds.

Best regards,
Restoration Rides

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