6.0 runs and quits

[Super73]

GM never intended a MAF based vehicles fail safe SD system to be the main program to run from. It is intended to get you off the freeway and home safely, then to get it fixed.


I have done my fair share of disconnected MAF driving, I am not afraid of any near term issues. However contrary to popular belief, a severely retarded tune up couple with excess fuel causes damage. It might not be right away but over time things can get ugly.

Washing cyls down
Excessive fuel IE Rich condition can cause predetonation
Add predetonation to fuel seeping between the rings and well so much for ringlands
Fuel in the oil


I am a big proponent of SD tuning, but not what is in the stock tune.


May I ask how long you have been "tuning" GM ECU's?

I am always learning and have been doing it since 2001.

The truck I race is in HPT 1bar SD mode
95% of the 200 cars I have tuned are in SD mode or i started there.

Originally Posted by davepl

I might agree with you, not sure. I think he has a mechanical/physical problem with what the MAF sees due to location in the tube or an air leak. I don't blame the tune, MAF, or ECM, I bet they're all fine.



I've never seen this. What ECMs do you believe cause this, as it would be important to avoid, but there's no info here. So far as I can tell the LS3 doesn't do that.

You'd want to fix the fallback timing table and clean up the VE if that's true, though I haven't actually encountered either, I'm by no means familiar with every GM ECM.

You guys are sorta funny - I've been daily driving the car you guys are afraid won't even run this whole thread! What doom and gloom! Of course I can only claim this for the LS3 but it works great.



Doesn't tell you what you think it does. Your tune is likely fine and both MAFs are fine, you either have a air leak like an unrestricted PCV or the MAF is sampling from a bad spot in your tube. It's one or the other. You'll need to fix it or run without the MAF.

Stop cleaning and replacing your MAF, there's nothing wrong with it!

[Wildkarde]

The only GM computers that don't default to low octane tables when the MAF is failed are the ones used in LS2 and LS7 applications. There's nothing wrong with running speed density if you need to because you are flowing too much airflow for your MAF sensor to handle or have a really monster cam, but just unplugging the MAF sensor is a terrible way to do it. Honestly going straight SD should be a last resort, the car will run better in most applications with the MAF. Especially E38/E67 Gen 4 stuff that rely even less on SD normally.

Not only are you running the low octane spark table, most of the LS engines including all of the gen 4 stuff has the IAT sensor included with the MAF sensor. The IAT sensor is a big part of airflow calcs when running speed density.

While your engine may run smoothly with the MAF unplugged dave, that doesn't mean it's running at anywhere near its peak. GM's VE tables, especially the virtual VE tables used in the E38/E67 computers are known to be fairly rich. This is a safety issue since things like clogged airfilters heavily effect the accuracy of SD, and while the narrowband O2's can correct this at idle/part throttle they are no help during PE. And rich is at least safe, or least until you get so rich you start washing cylinders down.

[4x4k30]

Originally Posted by 4x4k30

I have not heard back from the tune guy yet . I did try another maf sensor that I had laying around and as soon as I pluged it up the engine stublemed and just cut off again . so that tells me something is not wired rite or tuned . I have another truck with a 2006 6.0 and it has the maf and runs fine. and I am gona try to unplug it and see how it runs with it unhooked I will try it tomorrow and post how it does with the maf unplugged its been a long cold and windy day in ga.

I talked with the guy who tuned my ecm and he told me he didn't remove any thing to alter the maf system . he did say though it should be ok to run without the maf sensor if it runs all right without it and said that I need to drive it for a while and get it up to operateing tempature and see if after a few runs try to hook the maf sensor back up and try it then. I am still running straight headers and will be towing it to my exhaust guy next week after that I will be driving it...i cant take that wide open header noise . so I will no more after getting the exhaust hooked back up and driving it. I did go out today and check for vacuum leakes and couldn't find any but when I first start it it acts like its loading up on fuel and will run ruff but it does slowly get to a smooth idle.but it still smells rich.but it does smooth out and stay running.so I am gona wait and see how it does . I was gona unhook the maf on my 77 6.0 to see how it does but thought better of it.its running fine as is so I aint touchin it.

[LeesTruk]

Open exhausts,eh? How close to the openings are the O2 sensors located? I'll bet they are seeing all that fresh air on reverse pulses, causing them to "see" a lean condition, then giving the PCM a rich command to the injectors, creating the over-rich gas smell and stumble. You need to look at live data and see what the O2's are doing

[Wildkarde]

yeah, you definitely need to get the exhaust buttoned up before you can really dig into this. open collectors will be hitting the O2's with tons of air making the computer think the engine is crazy lean.

[4x4k30]

Originally Posted by Wildkarde

yeah, you definitely need to get the exhaust buttoned up before you can really dig into this. open collectors will be hitting the O2's with tons of air making the computer think the engine is crazy lean.

I got the exhaust hooked up and I have been driving it all week and it still will not run with the maf hooked up . it runs ok with it not hooked up but it has low power . I keep getting a p0102 code maf low circuit I have checked all the wiring and found nothing . I checked the pvc its seems fine too and I cant find any vacuum leakes I don't know what else to do

[Wildkarde]

How did you check for vacuum leaks? The best way I have found is to lightly spritz carb cleaner around all the areas that can leak and listen for the engine rpm to spike. Gotta check all the vacuum hoses, the throttle body, the intake gaskets at the heads (known to leak on these motors), and all the air intake between the throttle body and Maf sensor.

If you are confident you don't ahve any vacuum leaks and the wiring is good you really need access to either a scan tool that can read real time data to check MAF hertz or a DMM that can read frequency. If you go the DMM route this is a good tutorial on how to do it. http://easyautodiagnostics.com/gm/3....sensor-tests-1