Trouble code 44

Chris97K1500 · August 8, 2004

My dad's 95 Z71 has been having trouble starting up and idling. It'll start, but usually dies. Once it gets going, it stumbles at take off. We bought an AutoXray 2000 and it showed the Trouble code 44, O2 sensor lean condition. So, is this an O2 problem, or something else. I believe the 95 trucks don't have 4, but 2 O2 sensors. Is this correct? After looking on the internet, code 44 could be set by a number of things. New cap, rotor, wires, plugs, MAF sensor has been put on, condition still occurs. Any ideas? Chris

Cool Zr2 · August 8, 2004

there is one O2 sensor, and its cheap, I bought ont for my air fuel guage and it was like 20 bucks, try replacing that first, it may have gone fubar.

GMCSierra04 · August 9, 2004

Before you go playing the parts replacing game, you should make sure you find out the cause of the lean condition. Test the O2 sensor to make sure it is working properly if it is then you need to move to the components that deturmine the A/F ratio during warm up (open loop operation). It is only when the truck is cold right or is it when its fully warmed up?

When trying to figure out what is causing this you have to think what will cause the lean condition. I could not see when a distributor cap, rotor, plugs or wires could cause a lean condition because if any of those parts were faulty then there would be a rich condition. Not all the fuel would be able to be properly burnt so it would have more unburnt fuel, making it rich. A faulty MAF sensor would effect idle until the computer goes into closed loop I believe. Check the fuel delivery system, fuel pump, filter and injectors. If you cycle the key on and off a few times before start up does it start eaiser? Let me know how things go.

Chris97K1500 · August 9, 2004

So, there is just one, I didn't want to get dirty yesterday or I could have just looked. Yeah, we replaced those items before we knew what was causing the problem. He was just hoping it just needed a tuneup, it's at the 200K mile mark and all those parts were originals except for plugs. After all this didn't help he bought the scanner, then we knew it was a trouble code 44. It stumbles at startups, it's fine once it warms up. It's starts with no problems, first try, no hesitation, just won't idle right. We'll be fixing it this week if the weather allows. Appreciate all the help. Chris

elgineddie · August 10, 2004

Hey Chris,

This is completely off topic but every time I see your trucks picture in your sig I think there is a tow rope hangin off the front bumper. It wasn't til today that I noticed it was a branch in the picture!

I gotta start staying away from my exhaust pipe cuz I'm obviously seeing things!!

Later,

Ed

Chris97K1500 · August 11, 2004

Yeah, that's from the pile of brush to be burnt from cleaning out the fence row. It does look that way! Chris

Nice Burb by the way!

citydriver · August 11, 2004

So, there is just one, I didn't want to get dirty yesterday or I could have just looked. Yeah, we replaced those items before we knew what was causing the problem. He was just hoping it just needed a tuneup, it's at the 200K mile mark and all those parts were originals except for plugs. After all this didn't help he bought the scanner, then we knew it was a trouble code 44. It stumbles at startups, it's fine once it warms up. It's starts with no problems, first try, no hesitation, just won't idle right. We'll be fixing it this week if the weather allows. Appreciate all the help. Chris

Almost sounds like a vacuum leak.....What engine does the truck have?

Cool Zr2 · August 11, 2004

Almost sounds like a vacuum leak.....What engine does the truck have?

Its dosen't matter, the 4.3,5.0,5.7 use the same wiring and emissions systems and computer, the only difference is the PROM...

Check that O2 sensor, just because it looks like it is working dosen't mean its sending the correct signals.

citydriver · August 12, 2004

Its dosen't matter, the 4.3,5.0,5.7 use the same wiring and emissions systems and computer, the only difference is the PROM...

Check that O2 sensor, just because it looks like it is working dosen't mean its sending the correct signals.

My '95 5.7L doesnt have a MAF sensor, it has a MAP sensor..thats why I got confused....It may be the O2 sensor, but it could also be carbon build up under the throttle body, a stuck open EGR valve or a bad vacuum line,or even a bad IAC motor, or a bad coolant temp sensor...those are some things to check if the new O2 doesnt fix it.

Chris97K1500 · August 13, 2004

Well we replaced the O2 sensor, nothing changed, so we'll be looking at other possible causes. Chris

citydriver · August 13, 2004

Well we replaced the O2 sensor, nothing changed, so we'll be looking at other possible causes. Chris

In addition to the other stuff I mentioned ealier, you might also want to check/clean the TBI injectors

Chris97K1500 · August 14, 2004

Well, we just replaced the EGR valve, another possible cause according to the code 44 SES light. Nothing changed, still idles horrible and it's actually gotten worse. What is an IAC motor you mentioned CityDriver? We check all hoses for a vaccum leak, but everything seems fine. Any ideas? Appreciate the help, thanks, Chris

budhayes3 · August 14, 2004

A lean condition can also be caused by a vacuum leak, or even an exhaust leak. A good O2 sensor senses oxygen only...if extra oxygen is allowed to enter the exhaust, like through a cracked manifold or leaking gasket, the O2 sensor will detect that oxygen and the ECM will trip the code. I wouldn't throw anymore parts at it until I was sure that everything else was working right. Do a visual inspection for any vacuum, exhaust leaks, etc., then test the O2 sensors. They do go bad, or even get "lazy" (a lazy O2 sensor will switch rich/lean too slowly, and give false readings). Also, make sure that there isn't any debris covering the holes on the O2 sensor...the sensor needs those holes to reference ambient O2 to O2 in the exhaust.

Keep us posted!

budhayes3 · August 14, 2004

Oh geez, I just realized that you already replaced the O2 sensor...sorry bout that (just woke up, slight hangover)...I'd still check for exhaust leaks though, and it never hurts to clean the injectors and fuel delivery system...

need coffee!

Chris97K1500 · August 14, 2004

No problem! We just checked the IAC motor to see if it was bad, it's not. It won't idle at all if it's unplugged. Now it'll start fine, but die pretty quick. The second time you start it, it'll idle perfect no problems. But, if you put it in gear and try to take off, it's like it's not getting gas, it'll stall. Does it everytime you stop and start to take off. It's fine once it'll get moving. I guess he's just going to have to take it to a shop. We've check around all gaskets (manifold, TB gasket was replaced, no areas of leaking, hoses seem fine as well). Any other ideas? Chris