Help understand these symptoms please! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bpmcgee · 12-08-2008, 12:54 PM

Hi,

My buddy has a 2000 1500 with the 5.3 gas engine in it. He's been experiencing rough idle/stalling when it's cold. He's also a couple of times gotten code P0171 (System too lean - bank 1).

I hooked it up to my AutoEnginuity yesterday after the truck was all warmed up. The short term fuel trim for bank 1 was between -1 and 1, while the short term fuel trim for bank 2 was about 145. Also, the Average Injector PWMs were way out balance on bank one vs. two.

So the scan tool seems to be saying that bank TWO has injector problems, and it's continually trying to richen that side. The DTC, though, said that bank ONE was too lean.

I logged the O2 sensor voltages, but I didn't have time to delve deeply into what was happening with them.

Any ideas?

Thanks,

B

retodd7711 · 12-10-2008, 08:25 PM

Have you changed your intake manifold gasket yet?
These motors were infamous for poor gaskets resulting in the codes and symptoms you described.

Blue_71 · 12-11-2008, 01:00 AM

99+ trucks are notorious for the injectors getting clogged. we have a fuel injector cleaning tool, that runs 75 psi of pressure instead of the normal 55-60. it usually fixes the problem your having

polevault1977 · 12-15-2008, 05:10 PM

I've got the same symptoms without throwing a code. I suspect intake gaskets. I'll be checking with the b12 in the next day or two. I bet it's a vacuum leak between intake and head. Only in the cold is my main clue. Time will tell. dkf

Blaze69 · 12-18-2008, 11:06 PM

Give an update when you can to see if changing the intake gaskets fix your problem. I'm on the short road to changing mine in the next week or two. So it would be nice to know what results you get.

12-08-2008, 12:54 PM	#1
bpmcgee Registered User Join Date: Mar 2003 Location: Northern Illinois Posts: 2,181	Help understand these symptoms please! Hi, My buddy has a 2000 1500 with the 5.3 gas engine in it. He's been experiencing rough idle/stalling when it's cold. He's also a couple of times gotten code P0171 (System too lean - bank 1). I hooked it up to my AutoEnginuity yesterday after the truck was all warmed up. The short term fuel trim for bank 1 was between -1 and 1, while the short term fuel trim for bank 2 was about 145. Also, the Average Injector PWMs were way out balance on bank one vs. two. So the scan tool seems to be saying that bank TWO has injector problems, and it's continually trying to richen that side. The DTC, though, said that bank ONE was too lean. I logged the O2 sensor voltages, but I didn't have time to delve deeply into what was happening with them. Any ideas? Thanks, B

12-10-2008, 08:25 PM	#2
retodd7711 chrome makes it go FASTER! Join Date: Feb 2007 Location: Cleveland Tennessee Posts: 2,884	Re: Help understand these symptoms please! Have you changed your intake manifold gasket yet? These motors were infamous for poor gaskets resulting in the codes and symptoms you described. __________________ She can't cook and she won't clean. But she looks good in a skirt and she brings me beer. She can stay for now. EDIT:: But she left me anyway, So forget her. 1962 GMC Stepside V6 4 speed My rolling resto thread http://67-72chevytrucks.com/vboard/s...d.php?t=324226 My old farm truck http://67-72chevytrucks.com/vboard/s...=1#post3465005

12-15-2008, 05:10 PM	#4
polevault1977 Pick'n up the pieces! Join Date: Sep 2002 Location: Marietta, Oklahoma Posts: 198	Re: Help understand these symptoms please! I've got the same symptoms without throwing a code. I suspect intake gaskets. I'll be checking with the b12 in the next day or two. I bet it's a vacuum leak between intake and head. Only in the cold is my main clue. Time will tell. dkf

12-18-2008, 11:06 PM	#5
Blaze69 Registered User Join Date: Apr 2001 Location: Arizona Posts: 147	Re: Help understand these symptoms please! Give an update when you can to see if changing the intake gaskets fix your problem. I'm on the short road to changing mine in the next week or two. So it would be nice to know what results you get. __________________ 1969 Blazer: 350/350, 4X4, HEI, Edlebrock carb/intake, dual flowmasters, np205, 3:07's and the rest is mostly stock. The front end disc swap is finally complete 2002 Z71 Tahoe. CAI, Flowmaster 40, Silverstars in high, low and fogs and a bunch of mods (upgrades) inside and out.



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