engine noise... thunking or deisel type noise

[buildingdoc]

so I have an 04 expy 4.6. between 1200-1800 rpm the engine sounds like it is straining and there is a thunking after the engine is up to temp. in all my searching i have found that it may be the cam phasers. but upon further searching I have found that I dont think i have cam phasers.... It appears that they came out on the 05 5.4l. I got my head under the truck and had someone recreate the sound. Sounds like the noise is originating at the right catalytic converter. But I want to be sure. Anyone had similar trouble and/or any tips on what to look for? I havent noticed any problems in fuel efficiency or power. no codes coming up. it has 131k and changed the oil about 1000 miles ago and changed the plugs within the past 5k. noise started about 2k miles ago.

any and all help would be apprecitated

 

[X.handyman89.X]

Hmmmm! sound like you might have to get a mechanics stethoscope. If you have no problems in your fuel mileage, power, or check engine light it's going to be very hard to find the problem. When the engine is cold, hit the catalytic with your hand or something like a rubber mallet (just dont hit to hard) and see if you hear a rattle.

 

[buildingdoc]

Well recently I have had a couple codes pop up. 0174, 171 and too rich at both o2 sensors... 4 total. I replaced the vacuum line from the back of the things to the pcv valve. Also the engine would die after starting at idle. Cleaned the maf but to no avail. Currently guzzling fuel like a top fuel dragster. Any ideas? Gas costs to much to drive is like this.

 

[buildingdoc]

Somewhat repaired... Replaced passenger side CATS. I hate California. Codes went away but truck still wouldn't hold idle. I just replaced the IAC as I had the throttle linkage shimmed to keep idle up at about 900 rpm. I removed the shims and it will stay running... but now I get a humming and I can feel a vibration on the intake, literally with my hand on it and I can hear it even with the radio on. all over it. K&N is a little filthy I admit but the noise only started after the IAC was replaced tonight. I is only at idle. The idle is a little jumpy as well. I am assuming that the PCM has to re-learn the idle position for the TPS since I had it shimmed for a few months. Any thoughts... oh and the filter is getting cleaned tomorrow.

 

[cleaningman94]

That happened to my brothers expedition. Supposedly his problem was a vaccum leak.

 

[1997SCEBFEX]

You mentioned the TPS, it may need replacing too. It will take a while to relearn. if you do replace it, follow the instructions...there's also a thread on here.
PanHandler.

 

[buildingdoc]

I just started a new thread. I replaced the IAC and now have a humming noise between the air filter and TB @ idle.