Weird Power Loss

So I'm having a weird power loss issue. I currently have 315,000 miles on my 4Runner. It's been pretty steady and reliable up until this point. Currently I have a CEL for a P0420. I have not replaced any O2 sensors or Catalytic Converters yet. It has been on for a while too. I know most people will say "Well, that's your issue right there.". The symptoms don't make sense though. I will be driving and upon acceleration it will almost stop and hesitate and then continue accelerating. Also, another weird thing is when I was driving in the parking lot yesterday, I would very quickly tap the throttle and take my foot off and the throttle would hang for a second or 2. Idle is fine in Park and Drive. Cruising is consistent. Overall lack of power though. Any thoughts? Am I overthinking it and it is the Catalytic Converter?

Thanks

 

Check for any blockage in the exhaust system, any blockage in the Cat can cause power loss.
An a over supply for needed fuel because of a problem sensor sending the wrong Info. to the computer, will cause unburnt fuel to build up on the surface of the Cat. causing a blockage.

 

Pardon my ignorance, but how would I check for blockages in the exhaust system? With a scope?

 

Since i had this guy living next door who had this same problem, i know the signs of the loss of power caused by the blockage of the Cat.
What he did was remove the Cat and sure enough it was covered he spent about three hours getting unblocked.

So with out an exhaust analyzer you just have to remove the Cat and look at it.

if you do a google search you find the over supply of fuel caused by a faulty fuel air sensor, causes many blocked Cats.

The guy was told by his dealer he needed the check engine code for his fuel air sensor needed replacing, and he needed a new Cat. he got a $7,000 quote so he did nothing.

Then he cleaned the original Cat. and he did get the fuel air sensor replaced.

 

How old is your TPS? Tons of driveability issues when the computer can't figure out where your foot is.

 

The original one is still on there.

 

I have an appointment at the Muffler Shop tomorrow morning. They will look and see if the cats are clogged.

 

So I went to the Muffler Shop this morning. He does not think the Catalytic Converter is causing the issue. He said it is indeed not running as efficient as it should and causing the code, but the issue that I'm having is probably something else. I appreciated the honesty.

Back to square one.

 

Throttle Positioning Sensor? I might be completely ignorant here, but the symptoms sound a lot like what happened to me in Grand Cherokee and that was the issue.

 

Yes. It's the sensor that tells the ecu where the throttle is. If it can't, then ecu just guesses and you get hesitations and surging and stalling. So when I see a few driveability symptoms that don't seem to relate...I tend to look at the TPS as being the issue.

 

@negusm Poorly worded response on my part. I was trying to confirm that was your suggestion, which I'd second for OP's benefit

 

The OP didn't state what year or engine his T4R is?
But I'm assuming since he posted in the 4th Gen forum he has a 4th Gen.

That being asked and said, just an FYI all 4th Gens either the V6 or V8 doesn't have a removable/replaceable TPS like earlier T4Rs, the TPS is built into the throttle body so if it's indeed bad you have to replace the entire throttle body.

I would if for no other reason than a maintenance item, clean the throttle body and the MAF sensor and see if that helps a little.

 

Ahhh. Didn't know that. Toyota doesn't sell the TPS for the third gen 2001-2002 either and wants you to buy the whole TB assembly for like $500. Looks like 2003 and on are a much simpler TB and cost a lot less.

Regardless, cleaning the TB and MAF are free so very good advice.

 

Try and see if you can determine whether you are running reach or lean. Do a through inspection of the intake manifolds...so you don't have vacuum sections or holes around it. Then look at the injection system and make sure there is no corrosion around it. Some thoughts there...

 

Few notes. When I did the spark plugs last week, they were all a little white on the tips, so I am running lean. I was also looking at OBD data on my drive and I have 4 charts logging voltage on B1S1, B1S2, B2S1, B2S2 and I am seeing absolutely no voltage changing on either of the Sensor 1's. Shouldn't this be varying just like Sensor 2's?

While I can agree that it does sound like a TPS issue, the TPS percentage is staying consistent. I was watching it while driving and there were no sudden spikes or anything. Especially when I set cruise control, it cruises and stays solid.

Sorry, it is a 2005 4.7.

 

What's your fuel trim numbers looking like?

 

I have not looked at them. What should I be looking for?

 

Short or Long term fuel trim will tell you if the ecu is trying to adjust the fuel mixture. It tells you if the ecu thinks you are lean or rich. They measure how much fuel is being added or subtracted from what the ecu thinks should be normal.