My 2.7 manual cuts horse power when throttling up

I replaced the crappy plastic coolant bypass tube a month ago (which required unplugging all of the engine bay cables and taking off the intake manifold). The truck drove ok right away. Now over the past 5 trips, I have been noticing a problem with a big loss of horse power.

Here's how it happens:

- When I push the throttle I can go at a low speed, and if I press my foot harder the vehicle sounds like something is rattling or whistling and the additional power cuts off.
- If I am on a level road, I can drive at low speed and get around ok.
- When I go up a hill, the vehicle struggles even at 2nd gear.
- On the freeway I can't get over 50 mph unless I am going down hill. The maximum mph has been going down on each trip.
- This problem is getting worse each time I drive like something is failing.


What I checked:

- I raised the wheels and rolled them and found that they roll with a slight resistance. I think it is normal.
- I let the afe filter sit in hot soapy water for an hour, rinsed and dried. It wasn't that dirty anyway.


I checked the threads here and google and got a few ideas:

- bad catalytic converter
- something failing (brakes, etc.) with the wheels

Appreciate any help.

 

Clogged Cat sounds very reasonable.

 

ok I'm willing to buy a new cat considering the truck has 190,000 miles and will need one at some point anyway. The problem is that it is over $1,200 from the dealer and appears to be over $700 for an aftermarket one (CARB). Does that sound right?

 

Check Amazon for a vehicle specific magnaflow direct replacement.. I have had good experiences with them.

 

I am going to get one of these two but I can't figure out the difference aside from one being smooth and the other having visible heat shields. Any idea if the smooth one has heat shields built in as well? It appears to be a newer model and i'd hate to have to buy a separate shield for both parts.

 

I would bring this to shop asap (if you can't do it) and have the cat back pressure tested. They have fittings that screw into the oxygen sensor ports and you can measure the input and output pressure across the converter with a gauge. $877.00 is a lot of money to spend on a guess. I'd even disconnect the exhaust first and see if it makes any difference.

 

That idea sounds good. I assume it will be $100 or so. I also assume that my cat is due for replacement based on the mileage.

The price is not $877. That was on magnaflow's website. I am looking at $800 or less. I found one at $570 that did not include California on it's option to ship. I'll call Monday. I really hate my state BTW!!!

 

Before you go spending any money, take the truck to an old school muffler shop. There are cheap tests that can be run to determine what the problem is.

 

Have you gone back through and retorqued everything that you took off to do the coolant bypass pipe? If you didn't have this issue before taking apart the intake side of the motor, but now you do, I would look to that before guessing that it's something that you didn't even touch.

At 190k miles, I'd be suspect of any vacuum line that you pulled off when you removed the intake, and I'd be looking for vacuum leaks. Do you have an Ultragauge or Scangauge? What is the air-fuel ratio doing when the motor is bogging?

 

I would also inspect any wiring that was disturbed. There may be a loose or unseated connector or the wire harness has contacted something hot and burned through.

 

1. try running a bottle of cataclean before buying a new cat setup cleans out the catshttps://youtu.be/3w-FrjMFKvs

 

Did you replace all the seals and gaskets when you did the swap.

 

Throwing a converter at a problem to see if it fixes it? Thats a pretty expensive way to diagnose an issue.

Is the CEL on?

is the intake plumbing intact, all the hose clamps tight?

 

Sounds more like a vacuum leak to me.

 

Thanks for the suggestions. I just ordered both O2 sensors (since I'm still on originals) , 4 spark plugs and that cat cleaner. I will pull the air cleaner off next weekend and search for something loose or not connected. Then I'll change the plugs and clean the fuel system. However, like I mentioned, this HP drop is getting worse every mile so I'm inclined to think that either the intake manifold gasket or throttle body gasket failed after removal or something else. I may have to pull all of the plugs and parts and reconnect to be sure. It started with freeway speeds and now just driving up my street incline it struggles to go 10 mph.

 

Is the check engine light on?

If you had a spark plug problem that was so bad the truck wouldn't even go uphill the check engine light would be flashing. Same thing with the oxygen sensors. If they were causing the engine to lack that much power you would have codes present.

If you want to diag this thing yourself, in my opinion, instead of buying parts i would use that money to get a little code reader that can look at some OBD data. Info regarding short /long term fuel trims would be especially helpful.

I know the oxygen sensors are original from 2006 but a code reader would allow you to easily test them and see if they are causing the problem

 

Update:

So I finally got a CEL a few days ago. I cleared it and forgot the code number exactly, but I think it was P0301 (misfire cylinder #1) and either P2440 or P2442 or similar (secondary injection system). My scanner gave me those results for "Toyota vehicles".


I spent the whole weekend redoing the steps I took to replace the coolant bypass tube. I removed the intake, throttle body and probably 20 plugs and a bunch of hoses. Nothing appeared disconnected. Then I reinstalled everything and changed out the spark plugs as well and O2 sensors. I also swapped the 2nd cylinder coil with the 1st coil to see if the coil itself is the issues.

Same issue remained after finished. I don't have a CEL yet now so can't comment on that. I drove down the street and instant lack of power with a noisy vibration sound after pushing the throttle past low. It really sounds like air is escaping somewhere.

I have no problem changing the CAT or having it diagnosed, but after the OBDII readings, I'm wondering if the secondary air injection system or #1 plug coil might be the issue.

 

Here are the two injection parts on my 2.7:

 

Unbolt the exhaust pipe from the manifold and go for a (noisy) test ride.

If the problem is a clogging cat or even muffler, this will relieve enough pressure to let it run well.

Your symptoms also describe a clogged fuel filter. At least on older vehicles. Not sure if the Tacoma has one that can be replaced outside of the tank.

 

After a lot of internet research, I think I know what's going on: limp mode

Anybody have experience with limp mode?