naterry

Gents,

I'm having an odd intermittent issue with my F. This has happened 3 times now. The first time it happened I thought I was imagining it, but the second time it was distinctive.

For reference I have an 08 with 30k miles, Sikky Headers, and the JoeZ exhaust/intake with random cats. Stock air filter.

Basically everything will be normal and then the exhaust note changes it's tone much lower. The exhaust note gets more "rumble-y" and the engine does not rev as freely. It happened again this morning on the way to work so I shifted into neutral and rev'd the motor see if I could tell any difference. It was definitely more hesitant to rev, but after revving it a few times the problem went away and it revved and sounded normal again.

I'm thinking it has something to do with the variable valve timing, but am new to these motors. Plan A is to reset the computer and see if it comes back.

Thoughts?

Thanks in advance,

Nate

rhy

iTrader: (2)

If you're a newb like me, plug in an OBD2 tool and see if there are any codes

By then hopefully someone more knowledgeable will chime in.

MRxSLAYx

What type of oil are you using?

naterry

Definitely, that's the plan tonight.

Mobil 1 5w30. Do you think it could be a clogged port somewhere in the VVT?

rtr01

Might sound dumb but having the a/c on changes the exhaust note significantly..... maybe one of the cats is bad and it got plugged a bit causing more backpressure.. I know the first thing I noticed with the headers was how much more freely the engine revs. But I would plug in an OBD2 reader before I guessed further. Luckily I have one so not a problem for me. If you have any tuner friends they might have a laptop interface.

naterry

Unfortunately not the AC. I'll scan it tonight and report back.

Thanks for the input guys!

N

DCoolBeans

I'm no expert but I'd:
-Scan for the codes
-If none found pull these fuses(reset ecu)
-Pull out the MAF and see if its dirty. It might need to be cleaned.
-I also read that when swaping out exhausts the 02 or A/F plugs might get WD40 on them or get dirty. If thats it clean them with electrical cleaner
-Wait for more detailed answers on this thread

MRxSLAYx

Thats what I was thinking, but I would only mention it if you were still using conventional oil. I know that there have been some talks of Mobil 1 not being optimal for toyota vvti, but I dont really know enough to comment extensively on the topic.

Dv8tion388

iTrader: (2)

Cats can go bad, burn up and clog the exhaust. Power will decrease and change the tone of the exhaust.

Just an idea...



~Dv8

thainsane

Does it sound like a Harley kinda? I'm not making a joke but if it does your air fuel ratio not right.

Juanca

iTrader: (5)

I've been using Mobil 1 since the first oil change, and at 50k miles the car runs perfect.

naterry

Update- It sounded wierd and revved slow on the way to the shop again so I checked the codes after work and nothing. No codes. Hit erase anyway in case of "soft codes". I also reset the ECU just in case. Then the car sounded and acted normal on the drive home. I hate intermittent symptoms.

Thanks, do you remember what specifically was bad about Mobil 1 with respect to the Toyota VVTi?

I've been thinking about this and it seems like a CAT clogging issue wouldn't be intermittent. If the CATS were clogging it would get gradually worse, right? -can't imagine them clogging and unclogging, but I may be misunderstanding the nature of CATS and how they get hot and "fire" ..

The sound change is definitely more "rumble-y" (sp?). It normally has a higher pitch and is raspier. That change is very distinctive and why I knew something was definitely different.

So, O2 sensors.. This seems like the most likely culprit. I overfilled the oil a little (~half a quart) and didn't realize it for a day on the last oil change. I drained it down to the right level the next day after work but suspect it may have fouled an O2. This is the only thing I can think of that would cause this intermittent behavior. -an O2 (or 2) on the way out.

Thanks for the inputs!

I think I'll replace the primary O2's and cross my fingers. Not looking forward to this with how tight it is between the headers and the frame rails..

Cheers,

N

naterry

While waiting for the new O2's I figured it would be worth taking a look at the CATs to see if they were the culprit. See below-


Here you can see the total failure on CAT number one. Upon closer inspection I found smaller pieces of the foil stuck to the rear valence of the car.


Here you can see a partial failure of the CAT core on CAT #2. Note the outer layers and how they appear to be higher in the exhaust than the center, with one layer already folding over..


These have been in the car for ~10 weeks of normal freeway commute driving. No tracking, no accidents, etc. At this point I would not be recommending Random Technology CATS in this configuration for this car.

One side note, I have been running a single Random Technology CAT in my track car for 5 years without any issues. It's a 7L small block pushing 590 to the wheels. Maybe something has changed in their manufacturing process..

darbs242

iTrader: (5)

Same thing happened to me.... Those cats suck, mine got logged in the x pipe and it had to be cut and re-welded to remove the cat remains

naterry

Interesting. Did you end up with a different CAT manufacturer or running stinky now?