I have a 02 lariat screw 4x4 5.4 triton w 162xxx miles. occasionly it makes a loud audible "ticking" noise comming from under the floorboards like where the cats/02 sensors are. There are no exhaust leaks of any kind. No SES lights either. I am thinking that it is the o2 sensors possibly starting to go bad. I have checked for vaccum leaks at the manifold and just about everywhere I can think of and the noise is definatly under the truck where the cats/o2 sensors are.


I know that I should have changed the 02 sensors at 100xxx miles. How hard is the upstream sensors to change? I have read on this forum and from some mechanic freinds of my Dad and myself that the downstream sensors really are just redundant.

please!!!

Also somtimes when I come to a stop the exhaust makes a thud feeling-like a u-joint going bad. not every time though and the truck will shudder slightly when it happends

plugs/coil packs changed last summer w/ OEM parts

 

I hate to say this, but it sounds like an exhaust leak. How do you know that there are no leaks?

 

My Dad and I have each phyiscally looked and felt the entire exhaust while the truck was running and while the engine is off. My Dads mechanic at work has looked and done the same. He is ASE certified and has driven my truck as well. We also have tried the brake cleaner trick where you spray it onto the exhaust when it is warm-nothing. The only thing that we can come up w/ is that of the low grade stainless steel Ford uses in the exhaust from the factory is starting to get "pourous" or that I have an o2 sensor fouled up and starting to go bad. It makes the "clicking" when I am driving on a grade or a steep hill right before the transmisson has to make a down shift to pull the grade. I change my transmisson fluid every 3 years on the dot. was changed last year along w the plugs/coil packs. I am stumped!

 

Sure it is not a manifold leak? Very likely even with them being infront of you rather than under the floorboard. Could be a loose heat shield also or some type of metal.

 

The best way to look for a leak is on a cold start. Start the truck cold of coarse, and then run your hands along every seam. If there is a leak, you will feel the gases popping out of the leak.

I also agree with Darren. Double check that your manifold is not leaking, or cracked.

 

Here is a thought... check your trans mount, I've heard that a bad trans mount can eventually cause exhaust manifold bolt issues. When you are under load it may be flexing causing the exhaust to leak at the "donuts" where the pipe hooks to the manifold.

Just a guess!

 

Mine's doing this too I think, light tick and worse at cold start. I think it's a sign I should get those long tubes, high flows and true duals I've been yapping about. I do want to make sure it's not a plug about to launch!!! I did just do my plugs this year though so? Something to consider also. As mine goes, I think a cat or 2's gone bad, plus o2's.

 

Check to see if you have all of your exhaust manifold studs still in place... Particularly on the rear cylinders... They like to break off for some reason..

Mitch

 

I have heard that before thank you for your input and I will check it out and thanks to all the the other that have posted on this!!

 

after searching on these forums I keep reading that a heat sheild might be loose? are these the covers from the cats? if so do they bolt or weld on? What is the procedure to tighten them up?

 

^ Did you even look at your self?