P0300 P0303 P0171 - diagnosing

The fuel trim numbers you posted above would suggest to me that the engine is in fuel control, if those numbers were caused by the AFR was "lying" I would expect to see signs of the truck running excessively rich (black smoke, fuel smell from the exhaust, rough idle, etc).

I would want to see MAF at idle, on a warm engine, no load idle (700-800 RPM) g/s should be close to engine displacement (3.4)

You could also do a VE test to see where the MAF is at WOT although being supercharged this test may be inconclusive.

What you do is a WOT pull though 1st gear, record peak RPM, MAF at peak RPM, and IAT, put that, your engine info, and the current barometric pressure in the calculator below.
Being boosted I would expect to see a value well over 100% but I'm not sure as I don't have much experience doing this test on a boosted engine.

https://atgtraining.com/atg-volumetric-efficiency-calculator/

 

When I replaced the head on the 3RZ, I was getting PO171. Turned out to be #4 injector was not completely seated causing a vacuum leak. Turned it side to side a few times and it straightened things out. Runs great now. Just an FYI.

 

Okay guys. I picked up a better-made smoke test tool than my stupid home made one. This one is showing me some very small leaks around the K&N intake pipe - at the MAF, upstream at a vac hose nipple, and right at the silicon cuff joining it to the throttle body. They are small, but I didn’t see them before.

Goes to show you a proper tool makes a difference.

another thing- the throttle body and upper end of the intake have a dirty, oily film inside them. Is that pretty common?

working on cleaning all of this and sealing up these leaks, then retesting with smoke again.

 

Yes- it's residue from the PCV. We all clean the TB and IAC periodically because of this.

 

Sealed 2 leaks along the air intake tube, one right at the throttle body. Also cleaned the MAF, again.

just ordered enough vacuum hose to replace all of them. I see a couple with cracked ends but the smoke test didn’t show leaks in the vacuum lines.

I reset codes and went for a 18 mile drive. p0171 code did not come back while driving but it did when I was back home idling in the driveway.

I ran my scan tool back home idling the warm engine and here’s what I’m seeing:

STFT is mainly between 0% and 4%
LTFT is pretty steady between 37.5% and 39.9%

I can do more smoke testing in the morning.

 

I just replaced them, but it can’t hurt to turn them back and forth a few times. How did you discover which injector had the vac leak?

 

VE test = 49.06%
Air temp 52°F
RPM 4800
MAF 11 lb/min
3.4 L

 

Thats a really low number, either your MAF sensor is really skewed, there's a big air leak between the MAF and throttle body, a circuit problem, or the engine can't breathe.
Is your MAF in the stock housing or do you have an aftermarket air intake?

 

It has a K&N intake pipe. I sealed up some leaks yesterday in the pipe, and this morning the seals should be dried so I'll do another smoke test.

 

That could be the problem, MAF sensors are calibrated for the diameter of the stock MAF housing and airflow characteristics of the stock intake piping.

If those numbers are accurate it would have to be a pretty substantial leak to throw it off that much.
What is the reading at a hot idle?

 

ran VE test again this morning.

30.09 in Hg
5100 rpm
17 lb/min
IAT 78°
VE= 74.84%

 

STFT is mainly between 0% and 4%
LTFT is pretty steady between 37.5% and 39.9%

Or were you asking about other numbers?

 

I just did another smoke test. The silicone seals I did to the intake yesterday have cured and there is no smoke at all leaking out now. I also did a 1 psi smoke test to the EVAP system, after clamping the yellow striped hose off. There is no leak at all at EVAP. I hear no air escaping my compressor tank whatsoever; it's holding pressure.

When I run the smoke test into the intake, or vacuum lines near throttle body, I can hear air leaving my shop compressor tank at a very low rate. I don't see smoke anywhere in the engine bay, though. Hose connections all look great, whereas previously I did have some faint smoke escaping at various hose joints. Nothing from valve gaskets or cylinder head gaskets that I can see or hear.

However, since I could hear air leaving my compressor tank, I know that it is going somewhere. I had forgotten to plug the exhaust. I stuffed some shop rags in the tailpipe and waited. After a couple minutes I climbed under the truck and I can see the faintest bit of smoke escaping exhaust welds at the cat and further down at a weld joint near the resonator. These were repair welds by a shop, not factory. The original factory TRD muffler looks great, no leaks in the factory pipe welds. Only where the line was cut to replace a cat or resonator.

Question - would a miniscule air leak at a weld joint near the cat and resonator cause problems with the engine producing power? Is this something I should get fixed? They're very, very small - about the size of a pin prick.

The O2 sensor next to the cat looks brand new, which reminded me that I did replace that about 18 months ago. Forgot about that.

I'm not sure what to try next. Even though the O2 sensor was replaced a little while ago, I'm going to see how to test it with my multimeter and do that next.

 

A tiny exhaust leak is unlikely your issue. I had exhaust visibly escaping from one of the cross over flanges that didn't throw a code.

Something that's often overlooked is the brake booster. Maybe try disconnecting that?

 

I was asking about the MAF reading.

 

Hot engine idle readings:

MAF fluctuating between 0.38 and 0.55 lb/min
RPM between 690-850

 

Thats fairly close maybe slighlty low for idle numbers, the guideline number for MAF at idle is g/s should be right at engine displacement (L) at 700-800 RPM.
Your at 2.8-4.2 g/s on a 3.4L engine.
The WOT numbers are very low though, do you have your stock intake piping and MAF housing to see if that's what's skewing the numbers?

 

No, unfortunately, I don't have stock intake air box and pipe. That's something I'd have to scrounge up.

* * * * *

I did just conduct some tests on the O2 sensor, at idle.

IDLING (Normal Operation)
O2 sensor voltage wide range sensor 1: 3.09v - 3.27v
O2 voltage sensor 2: 0.03v - 0.06v

TOO MUCH AIR (PCV hose disconnected)
O2 sensor voltage wide range sensor 1: 3.93v - 4.17v
O2 voltage sensor 2: 0v

NOT ENOUGH AIR (air intake partially blocked)
O2 sensor voltage wide range sensor 1: 3.2v - 3.6v
O2 voltage sensor 2: 0.018v - 0.7v

 

My scanner was reading MAF as lbs/min, but I can change it to g/s and take another warm engine idle reading...

 

g/s is a little more accurate but it can be converted, 1 lb/min = 7.56 g/s
I'm curious if this problem started after you installed the aftermarket intake.