Lean exhaust and other codes

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Schurkey

Supporting Member
Supporting Member
Joined
Jan 14, 2018
Messages
10,970
Reaction score
13,756
Location
The Seasonally Frozen Wastelands
I use an ancient Snap-On MTG2500 "Red Brick" scan tool. The more-common MT2500 is very similar but doesn't have the graphing feature.

The OTC Genysis is also very popular, but I've never used one.
 

ouray19

Newbie
Joined
Nov 21, 2013
Messages
30
Reaction score
2
Location
Colorado Springs, CO
Would like to revisit this thread since I am still having an issue my truck. Runs good when I first start it up but after it gets warm, it becomes sluggish and stumbles when I first take off from a stop. Runs rough until I get up to about 2500 rpm's and then kicks in and runs strong. I do get an occasional code 44, lean exhaust, but does not seem to change the way the truck runs. Just looking for some input or thoughts on where I might start looking to resolve this issue. Thanks in advance.
 

Schurkey

Supporting Member
Supporting Member
Joined
Jan 14, 2018
Messages
10,970
Reaction score
13,756
Location
The Seasonally Frozen Wastelands
What did you find when you examined the data stream?

Good short- and long-term fuel trim numbers?
Good O2 crosscounts?
Accurate coolant temperature sensor?
Anything stand out as unusual? Whatever happened to the low voltage problem? When you fixed that the first time, the problems went away. Sure you don't have a low-voltage problem again?

Without looking at the data stream and verifying the starting/charging/battery system, you're just shooting in the dark.
 
Joined
Dec 10, 2016
Messages
518
Reaction score
160
Location
Hampton, VA
Fuel pressure is among the first things I'd check, not if all else fails. Timing doesn't change once it's set, but fuel pressure will. Does the 95 have 2 O2 sensors? If so, which one? Bank one is left and bank 2 is right. IIRC the left injectoe feeds bank 2 and right injector bank 1. Obviously a throttle body would alleviate an injector issue. Good time to do the TBI mods.
Each injector feeds two cylinders on each bank.
Check for weird voltage and grounds again.
I use win aldl for live data there are other similar programs if you have a laptop and can get a cable. Cheap way to get to live data.
And before you go chasing your tail, check on the health of the motor. Do a compression test or leakdown test and see where you stand. I used to have a 95 4.3 v6 truck that had a cylinder that wouldn't reliably light below 1800ish rpm. Had my fuel trims all maxed out trying to correct my "lean exhaust". the ecm only sees the excess oxygen in the exhaust,not all of the unburnt fuel that also comes from a dead cylinder, causing the ecm to try to correct by pouring on the fuel.

Really not much to do until you can figure out the health of the motor, and what the hell the computer is looking at.
 
Joined
Dec 10, 2016
Messages
518
Reaction score
160
Location
Hampton, VA
One more thing, Jump terminals A and B on the aldl just like you are trying to read codes. But this time start and drive the truck, you will notice the CEL flashing fast, this indicates that you are operating in open loop, i.e. no feedback from 02 sensor. when the truck starts running like ****, look at the CEL to see if it is blinking slower, this indicates closed loop operation, i.e. feedback from 02. Try to see if the driveability issues coincide with the change from open to closed loop. Of course, do this test from a dead cold motor. This ability is called field diagnostic mode and is an often overlooked feature on these trucks.
 

ouray19

Newbie
Joined
Nov 21, 2013
Messages
30
Reaction score
2
Location
Colorado Springs, CO
Thanks for all your suggestions and inputs. Will look again at all my positive/ negative connections. Alternator, battery and coil all test good. Still need to put a good data tester on but the CTS ohms out correct at different temps. Will pull compressions over the next couple days.

Did not know you could run the truck with the A-B jumper in place. Didn't think you were supposed to start the truck with the jumper in place, just turn the key to on.

Thanks again for all the input. Will keep working on it.
 
Top