Question on lean condition

[pete57]

Originally Posted by tbrown5079

I use my truck just as a means of transportation. Trips to the hardware, walmart, cruise around town or go see a friend. never wot. It runs great. After I drive it several times (50 miles or so ) just as I am putting it away, I notice the check engine light is on. If you look at my buildsite, I do have a 180 degree bend in the intake pipe from the air cleaner. Full 4" pipe, but could that cause an issue with the MAF sensor that would trigger a lean condition? Also, it doesn't seem like I am getting real good gas mileage and smells rich when I pull it into the garage. Puzzling, and I would like to get it resolved, which is why I was interested in pete57's post. Thanks for the come back. Maybe we can both learn something. tbrown

Yeah, same with mine. Only throws the codes after i drive it for a few miles. Runs great other than that. I was thinking on the bigger air intake pipe and open element also, plus long tube headers on mine, maybe its just not tuned right.?. My 1st time really trouble shooting a newer computer control engine like this.

[davepl]

Originally Posted by pete57

Yes, it has the MAF. Ive tried cleaning it a couple of times but no change. I do have on open element on it, could it be getting too much air?

I doubt it's dirty. Have you tried UNPLUGGING it as I mentioned (while off) and then trying to start and run it?

Most GM computers will operate this way and it allows you to determine if your problem is in the intake pipe or MAF. If it runs better with the MAF disconnected, that's your issue. If it's the same or worse with the MAF disconnected, then you can rule it out. Either way you know something new that you didn't know before.

[pete57]

Originally Posted by davepl

I doubt it's dirty. Have you tried UNPLUGGING it as I mentioned (while off) and then trying to start and run it?

Most GM computers will operate this way and it allows you to determine if your problem is in the intake pipe or MAF. If it runs better with the MAF disconnected, that's your issue. If it's the same or worse with the MAF disconnected, then you can rule it out. Either way you know something new that you didn't know before.

Im gonna try to get it out and drive it tomorrow to see if the codes come back, will try unplugging the maf also. Im hopeing that cracked pcv hose was the problem but we'll see if i get that lucky.

[tbrown5079]

I will try unplugging mine also. Only trouble is we had about 8" of snow here yesterday and I'm not taking it out until the roads are dry. I really don't want to horn in on your thread pete57, but this is so close to my issue I really appreciate the info. tbrown.

[Kudzupatch]

Originally Posted by mongocanfly

Lane was who I used...and would again....bunch of guys I work with are into rock bouncing and he's the only one they'll use....the day before I was there Big Chief from street outlaws had the crow on his dyno....you could still smell the nitro

Was following this thread and wanted to say thanks for tip on Lane. Getting ready to do a swap in my Suburban. Wanted to use an L31 crate and keep the TBI for simplicity. Was concerned about tuning and dropped him a line. he is the first one willing to work with me since this is OBD1. Had not heard of him before.

[pete57]

Originally Posted by tbrown5079

I will try unplugging mine also. Only trouble is we had about 8" of snow here yesterday and I'm not taking it out until the roads are dry. I really don't want to horn in on your thread pete57, but this is so close to my issue I really appreciate the info. tbrown.

Please horn in, maybe between 2 of us working on it and help from these knowledgeable guys we can get it fixed. Cruising seasons coming up quick

[tbrown5079]

OK, thanks. I will be out of town for a few days but will get back to you. Would really like to get this solved also. tbrown

[sprint_9]

What are your O2 sensors like? Are they all hooked up? Each one to the proper side? And is your tune set up for the number of O2 sensors that you have?

[tbrown5079]

I have mine installed just as the harness came back from the tuner. It was a low mileage motor ( 27,000 miles ) so I figured they were ok.I guess there is a chance they could have been marked wrong and are on the wrong side. tbrown

[mongocanfly]

the o2 cables should have been marked left and right...

[tbrown5079]

They were, and pretty darn sure I would have put them on their right sides. A possibility though. Thanks for the thought. tbrown

[robertsjm711]

It would be interesting to see where the long (& maybe short) term fuel trims sit at for idle, mid & high rpms. And are the fuel injectors stock size? My tune place (LT1swap) wanted the serial #s for the programming.

I also would look the MAF & O2 reading. http://easyautodiagnostics.com/gm/4....e-maf-sensor-1
I have a simple phone app & ob2 module (~$20) based reader that can look at real time sensor info. I had a rich condition from my passenger O2 sensor signal wire having a bad connection. Hours of swapping sensors, tracing wires...

What do the spark plugs look like - super white? consistent with all of them? Could point to if you actually have a lean condition or it thinks you have one (less likely).

Does unhooking O2 sensors force open loop? If so you could compare open & closed loop fuel trims. If both sides do the same thing, it would point to something common like MAF or programming, and maybe eliminate O2 or injectors.

Make sure you don't' have a sneaky vacuum leak. You can use a smoke machine or my preferred super unsafe carb cleaner soak down method. Spray, & if rpms increase you have a leak. Keep fire extinguisher handy.

Mildly unrelated - when I first started my 5.3 I had the MAF backwards - she did not like that one bit... When diagnosing these things I don't look for that is wrong, but what is working correct and eliminating it as a fault. Makes me look at the system as a whole, not separate parts.

[pete57]

Ok, think i might have found my problem. Split hose between pcv and hard plastic line to top of manifold. It was really sucking some air. Replaced it with a short piece i had laying around. Been driving it around for the past 2 days and no check engine light or codes have poped up, running good. I did try unplugging the MAF and all it really did was throw more codes, it didnt like it. Thanks for the help everybody, hope this can help some other folks too.

[mongocanfly]

glad you found it.....

[Hart_Rod]

Originally Posted by mongocanfly

Lane was who I used...and would again....bunch of guys I work with are into rock bouncing and he's the only one they'll use....the day before I was there Big Chief from street outlaws had the crow on his dyno....you could still smell the nitro

Do you have Lane's contact information? Thanks,

Rob

[mongocanfly]

sure do....http://culverautospecialties.com/

[Hart_Rod]

Originally Posted by mongocanfly

sure do....http://culverautospecialties.com/

Thanks!