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3 Posts
Discussion Starter · #1 · (Edited)
Power Loss... NO Codes...

2003 Santa Fe 3.5L gas
140,000 miles
Timing belt replaced 2010
Plugs and wires replaced 2010

Air filter is clean... nothing dirty in the MAF .

About a year ago I was towing my empty 5x8 trailer on a 2.5 hour trip to the beach...
I had a sudden loss of power and a hard time getting past 60mph even on the flats with the trailer in tow.
Since then I can get up to 75 or so, the acceleration is like driving a huge semi-truck trailer... so I don't even try that speed, because as soon as I get there I have to slow down for something.

No Codes.
There is a video in one of the threads about Catalytic testing...
As to the video...
I checked with a scanner tool the upper O2 sensor volts fluctuated as in the video... although the lower O2 sensor volts fluctuated between .18 and .72 . Which according to the video was not so good.

But no codes.

I took temperature temps of the lower Catalytic at the red dots in the pictures and they were close to 450' F at the locations.

I guess I really need temps of the upper Catalytic too.. later today.

Ok.. No Codes.
I had the MAF off last week while putting in a new master cyclinder...
Just to sort of check it, I started the engine... it wouldn't start so much.. putting the MAF back on started right up.

Possible solutions and comments please :)
TPS Throttle position sensor... ? how would I test it ?
Crankshaft Position Sensor... ? testing ?
MAF... don't think it that.. but maybe so...

Car runs basically ok... but no acceleration.. no "power."
Gas mileage isn't too bad.
I get better than 20mph if I keep it under 60 on the highway..
16mpg to 18mpg around town if I don't race around.

I also ran two cans of that BG gas product back in the late Winter.
And then also ran SeaFoam stuff in the gas tank only in the Spring.

Thanks a bunch group... welcoming all and any advise.

Also.. in the first picture below the "mesh" connecting section area looks a little "puffy" and in one video I saw a guy said that is where on his a bunch of junk had collected and made his puff up too.


3 Posts
Same as me???

Sounds like one of the several things I encountered. Check your muffler by kicking it. Most likely it is getting clogged as they are known to gather condensed water and then rust and collapse. If no go then you could have a clogged CAT.:eek:

3 Posts
Discussion Starter · #3 ·
Well I did "kick" the muffler and there is a fair amount of rattling going around inside. I did order one just now.

It does make sense with enough back pressure to cause the loss of power with acceleration... but enough release pressure to operate well at 0-30 mph... and under 2000 rpm's.
Not that I know anything about this.

Thanks... we'll just have to see how it goes.

3 Posts
Discussion Starter · #5 · (Edited)
take her for a spin with the muffler cut off in the meantime and see if that was the issue

Well at first I thought you were just being a comedian.. :00000732:

But in reality it was a good suggestion...

I did order a new muffler assembly from Advanced Auto online and got it in a day and half delivered to my front door... faster than I thought.. I was going to go fishing... but since the muffler assembly came so fast I took on the task.

Installing the new muffler..maybe I shook something to the maximum in the catalytic converter... now I had the worst power / acceleration . I disconnected the muffler... and the sound was the same... as if there was a muffler installed, a little better on the acceleration. But definite back pressure.

I bought a cheap vacuum/pressure tester.. checked before and behind the downstream of the rear catalytic converter and figured out it was completely clogged.

It was... replaced.. and it feels like I am driving a Ferrari...

Before I pressure tested and took out the downstream catalytic converter... I called the Tenneco/Walker Tech Help Line (muffler I bought) he told me that the downstream catalytic was probably clogged... and because it was far enough down from the rear O2 sensors, it wasn't displaying a code.

I might get a code now with the proper exhaust flow... but for now there is no back pressure and runs like a champion.

And still no codes, which for now tells me the upstream catalytic converter doesn't need to be replaced.

I could have saved some money not replacing the muffler by pressure testing the before and after sides of the downstream catalytic...
But the muffler was cheap enough and not too bad to replace.. and I know I have a good muffler that won't be a problem.

Hope this helps anybody else with no codes, loss of power, clogged downstream catalytic.

Now I need to get back to some fishing on the Chesapeake Bay.

Thanks group !

17,552 Posts
Status of plugs and wires ?

When last replaced and what kind ?

Any previous misfire history that would lead to previous advanced primary catalyst degradation ?

Primary cat will fall aprt and chunks/dust flow downstream and clog inlet to down stream cat.. Remove front pipe and inspect from bottom the primary cats, and see if anything in the front pipe that will fall out.

Aftermarket pipes if bucket of troubles, poor fit, pipe sizing, muffler sounds (we had one where body shop went cut rate <likely by insurance demands> and was loud as all get out with customer complaint) and hitting AWD driveshaft

Other source of pedal loss is APS,, we see them crap out when cold on XG and Santa Fe 3.5, leaves a couple weird pedal codes and 1 or 2 limp code.. read codes slowly and carefully when it come to 3.5 ETS system.. customer thought he be smart and ordered wrong part (I knew it when asked to install the part), did not remedy, he mad, came back finally and paid for my scan and diag, left repaired when I was done
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