2005 2TR-FE 2.7L RPMs Fluctuating at Idle and Loss of Power

Like the title says, I have a 2005 with the 2TR-FE engine. At idle the RPMs fluctuate almost like it is about to stall. When I drive the truck it feels like the truck is hiccuping when I give it gas. It will have the normal amount of power and then the power will drop off then pickup again.

What I know so far.

I have a P0420 engine code (I had the code before I changed the Cat and after I rest the code)
-MAF Replaced (Denso)
-O2 sensors replaced (Denso)
-Catalytic Converter Replaced (AFE)
- Coils and plugs replaced not long ago

Long Term Fuel Trim is. -15
Short Term Fuel Trim is. 2

So it thinks its running rich but I cant seem to figure out why.

I am open to any suggestions of what the cause might be.

 

Bump

 

Check fuel pressure

 

Fuel Pressure is fine.

 

Update:

I have taken it to two local shops and they haven't been able to provide anything useful as to what the cause is.

One shop did an exhaust leak test and it didn't have any leaks.
They also checked if the 02 sensors were getting proper voltage and they were.

I cleaned my throttle body and that seemed to have helped but I am a little skeptical if that was the cause or if it was just one part of the problem.

So right now it seems to be ok as far as not getting any power loss but my idle is still fluctuating.

 

How much fluctuation are you getting? Is it trying to stall?

With a LTFT of -15, you're running really rich. Is your idle high? Have you checked for vacuum leaks? Do you have a Scangauge or something else to constantly monitor your fuel trims? Has the LTFT dropped since replacing the cat and o2 sensor? You could also have a leaking injector.

The idle fluctuates in my truck too, but I've never noticed power loss. I suspect my fluctuations are the AC compressor cycling, but I've never bothered looking into it.

 

Idle isnt high but I would say it fluctuates around 900-500 rpm. I had a few ocassions where it came really close to stalling but never fully stalled. I have checked for vacuum leaks to best of my ability. I even tried spraying starting fluid in areas to see if it would fluctuate but I couldn't find anything.

I have an ultragauge and I constantly monitor my STFT and LTFT as well as O2 Temps and MAF Voltage.

LTFT hasn't dropped off after replacing the O2 senors and Cat.

I took a video of what it was doing, I will see if I can upload it.

 

https://drive.google.com/file/d/1mtGeveAiqmfaZ7LjPkZaFE0yS1pimels/view?usp=sharing

This was during my first startup of the day so the RPMs are going to be higher than usual. But you can see that there is an issue.

 

That sounds a lit like the fluctuations that I get, but I've never thought it was going to stall.

Have you disconnected the battery to reset the ECU? That smooths out the fluctuations for awhile. It will also rest the fuel trims. It can take awhile for the LTFT to adjust if you don't drive a lot.

 

I disconnected the battery when I installed everything so it should have been long enough to reset the ECU. I drive quite a bit for my job so the adjustment period shouldn't take that long for me.

The idle fluctuating doesn't bother me but I feel like it is a symptom. The power loss and the potential of stalling has me concerned more than anything.

 

Mine does the same thing after changing upstream 02 sensor and cleaning out the catalytic converter. When it's cold all numbers seem fine and the cat monitor says that it's manufacturer spec. But when it's been warmed up and restarted I will notice the cat monitor bank 1 decreasing in number till it spits out a p0420.

I might need to increase the tension on those bolt springs at the flange where the exhaust manifold pipe connects to the cat or reseal that gasket with a new graphite O-ring.

Did you try starter fluid on the PCV line and run carb cleaner through it? Maybe the fuel injectors need cleaning.

If those are fine, maybe it's the EGR. After 10 years, these things are coated with carbon.

 

Fixed the rough Idle problem. Throttle body had buildup around the plates. Turns out last oil change, they added more oil than I needed and most of that excess blew through the PCV valve and into the throttle body vacuum port when I went over 4000 RPM passing a semi on a 75mph highway. It clogged the already broken element in the upstream catalytic converter.

Ignition coils 2 and 4 had a small amount of oil on them. It's at 340K miles and Spark plugs were never changed since new. The plugs had a ring of light brown oil deposits on the glass end. The spark plugs themselves felt like they were loose. The sparky end had some kind of light brown coffee colored deposits on all plugs. I think a little of that oil at high RPM pushed through plastic valve cover and gaskets and into the spark plug well or the plugs were so loose that a small amount of combustion gasses escaped and condensed on the ignition coils. At high heat the ignition coil would form carbon deposits and foul the timing, leading to misfires and extra fuel and oil condensing in the core of the catalytic converter. Plugs 2 and 3 had resistances of 9k Ohms when they should be at 5k Ohms. After changing plugs, it still misfires when cold but not when warmed up. So it looks like I'll have to change the ignition coils too.

I think your issue may be fuel injectors. That's next on my list. Air-Fuel ratio commanded at 14.7 but actual is around 14.6. It's a little rich but not by much and I'm not getting any other codes. Vapor pressure fluctuates around 24 mmHg [48psi] so fuel pressure is slightly less but not constant. I think it should be at 50 PSI. This may be a nothing burger or it could be the fuel filter is clogged slightly clogged or the fuel pump itself is contaminated with rust.

Have you checked the timing chain on yours?