P0101, P0171, and P0174 engine codes.

[MikeInCtown]

I posted this in the 99-06 area but didn't get much help. hoping someone can assure me or point me in a new direction. here are the original posts. Thank you!

 

truck is a 2004 Sierra 2WD step side extended cab with the 5.3 T Vin and 204,000 miles on it.

 

 

Truck is 2004 Sierra 2wd with the 5,3 T engine and 204,000 miles.

Prior to these codes set I was getting an evap solenoid code of 0446 IIRC. This past weekend I put a $20 Delco evap solenoid on it to see if that would solve my problem so I can get emissions tested. (skipped buying the one with the long hose and filter) Anyway, when I pulled out of the shop I was working in, my CEL illuminated again with the three codes. (the 0446 has not illuminated for me since my evap solenoid replacement on the rear of the tank)

 

The freeze frame data showed the fuel trims very high and an engine temp of 143.

I plugged in my Innova scanner and went for a couple rides over the next few days and found that when cold, the STFT on both banks were near 10 while the LTFT on both banks would be near 20, bouncing between 10 and 25.

 

When the engine warmed and at idle, the STFT AND LTFT would both be at or near zero. However, when I was driving with a throttle position of between 20 and 35, the LTFT would run between 10 and 19 and the STFT would be below 10.

 

I initially thought based on reading that I had an intake leak, However wouldn't the fuel trims be lower with the engine hot and the engine getting 25% throttle? I just visually checked the intake at the MAF and the throttle body and both connections look well on and very tight. I can also hear my fuel pump whirring away with a strange squeal so I thought that maybe my fuel pressure was low, but when I hooked up my gauge I am getting 55 PSI at key on, and 60PSI at cold start idle. (when the codes have all set for me)

 

A question was then asked of what data was I getting. From the freeze frame data available through my Innova tool...

 

 

According to the freeze frame data on the most recent code reset the values are as follows;

 

load 14.1

ECT (F) 87

STFT B1 11.7

LTFT B1 17.1

STFT B2 12.5

LTFT B2 17.9

MAP 19.1

ENG RPM 1819

Veh Speed 24

MAF (lb/min) 4.629

TPS 29.0

 

 

I just got back in from giving it a once over. I loosened and then tightened both intake connections after the MAF and at the throttle body. I also took a torque wrench and made sure the bolts were tightened to spec. Three moved maybe an 1/8 turn but one on the passenger side I think maybe bolt #1 turned a good half turn if not a little more before I got the click.I then poured a gatorade bottle full of water all over the intake mounting locations on both sides and the engine didn't so much as stutter once.

 

I started the truck back up and the 0171 and 0174 codes were gone but the 0101 code was still present with the data I just wrote.

 

Went for a 15 minute drive watching the live data. At idle and 550-600 RPM the trims are all at 0 or even in the - range. At throttle/acceleration I watch them go to 20-25 on the LTFT but stay less than 10 on the STFT. Wish I could post a photo of what all the values are but trying to drive and glance at the scanner is hard enough.

 

And my last post in the thread said

 

Changed out the MAF to one I had in the garage from when I had a K&N intake on the truck. After the change, the LTFT numbers were better, in the -% range, but as soon as I touched the gas to move, the LTFT numbers would go to 17% instantly. I've made sure the intake is on good and tight, so I'm not sure what else could be causing my issues besides manifold gasket issue??

 

 

So what I've done is change the MAF sensor and cleaned it. At the same time I made sure the intake from filter box to throttle body was clean and well tightened. I also tried to make sure the intake bolts were tightened to spec, and in the process I found one was between 1/2 and 1 turn loose.

 

Once I did that last bit of work, the STFT stays under 10% and actually hovers around 0, give or take 5%. the LTFT on both banks though sit near zero at idle, but as soon as i give it any throttle, the trims shoot to 17% almost instantly. the STFT does stay near the same however, even with partial throttle. Also, the 0171 and 0174 codes did not reset in the couple trips I made, but the 0101 code did reset almost immediately. I've since had to pull the battery and charge it as there is a wiring issue which drains the battery if not used every few days. have not driven it in 2 weeks now.

 

I bought a new set of FelPro intake gaskets and plan on doing the intake this weekend. As I don't have access to a smoke machine I am flying blind based on what I have read and watched on line. I tried pouring water around the edges of the intake with no noticable change in idle condition as one may expect if there was a bad leak. A local shop can hook up the smoke machine and test for $100, but before I spend that $100+ I want to be sure I have exhausted all my options that I can check myself.

 

If anyone can recommend a couple more checks i would very much appreciate it. I am sure you have all witnessed this trouble before and can say with probably 90% accuracy what the problem is, but I need the vote of confidence.