LS6427

iTrader: (2)

So, my engine is old. But runs like a top. I never really cared because it runs so damn good. I know its been running rich for awhile because my bumper gets black above my tailpipes after about a week, and when I nail the throttle from a roll I get a little black smoke. (black)

About 3 years ago I unplugged my MAF when the engine was off and cold. I started it up and went for a drive for about 25 minutes. The engine/car ran 100% the same as it always had. So I figured my MAF had failed. I got a new one, hooked it up and "no" difference. I then unplugged that new MAF and "no" difference. I was told that my PCM defaulted to a SD tune....????

So I have been running MAF'less for a few years. I bought a new MAF again last week, hooked it up and again "no" change. Engine operates normally and pretty much perfect, except for it does need about 1 full minute to warm up when cold before I take off. The rpm's jump around for about 1 minute before they settle. But after that its all normal.

QUESTION:
How do I get my PCM to recognize and utilize the new MAF again...its like it refuses to use it.....???? It would be nice to not run so rich.
I disconnected the battery for more than 30 minutes to reset the PCM, didn't do anything.

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cause4panic

iTrader: (2)

you need to look at what your o2 sensors are doing.

LS6427

iTrader: (2)

They are new if that matters.

If I'm getting alot of blow-by just because the engine is so old....would that cause it to take the MAF out of the loop and run on a SD tune?


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HUNTER02SS

iTrader: (24)

Have you ever had the car tuned?

LS6427

iTrader: (2)

Oh yes.....when the engine was installed back in 2002 it was fully dyno tuned. Ran great till about 2007 when I started to notice some oil burn and a little black soot build-up on my rear bumper. Still ran great though.

I assumed it was just blow-by from high miles on a stroker motor. Now I have over 130,000 miles on it...so I know I have blow-by going on, and probably alot. The engine runs great, absolutley no smoke comes out of the pipes unless I literally go WOT from a roll. From a dig, it will never make smoke if I go WOT. Just from a roll.

I thought the MAF operated for cold starts...and when you go WOT after its warmed up. So I figured getting a new MAF would at least stop it from running rich.

But if I'm chasing my tail because my engine is just so damn old for a stroker motor....I won't worry about it. I can wipe my bumper off once a week and just stay in a SD tune mode. It literally runs great other than that.

I've had a Z06 MAF on there since 2002 using that adapter pigtail.

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HUNTER02SS

iTrader: (24)

The reason I asked is when the car is tuned, your supposed to tune the VE table first and also set the parameters for the MAF to where the MAF has no effect on the VE fueling.So with that said, I was wondering when the tune was finished up, did they reset all the values back to where they were to allow the MAF to work again. They should have, since after the VE tuning, you tune the MAF. Do you know if you have a SD tune or is this what someone just told you?

LS6427

iTrader: (2)

It was definitely tuned with the MAF. I know this for sure because the shop that installed my 427ci sold me the Z06 MAF. All I had was my stock MAF, I forgot to buy a better aftermarket MAF so I went ahead and bought it, then it was tuned like that.

About the SD tune....I had asked on here a long time ago and someone said that when a MAF fails and its not replaced, the PCM will default to a SD tune. Is that true? Because like I said, it runs perfectly normal and just fine. I just get the black cloud at WOT and it needs to warm up for about 1 minute.

Can the PCM take the MAF out of the loop totally and make it run more rich....if I have too much blow-by messing with the fuel/air mixture too much...?


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HUNTER02SS

iTrader: (24)

When the MAF fails it reverts to the VE table. So if your MAF is not working and your VE is not setup properly, yes you can be rich and or lean. The ECU cannot just take the MAF out on its own. You would either have to set the values that operate the MAF to have it not work or the MAF is just bad.

LS6427

iTrader: (2)

Thats whats wierd....I put this new MAF on (the second new MAF attempt) and it does absolutely nothing. Engine operates identically. So somethingt is causing the MAF to NOT get back into the game.

How can I check to see if signal is getting through the wires/plugs for the MAF to the PCM? Maybe I just have a bad wiring issue.

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HUNTER02SS

iTrader: (24)

I cannot remember what color wire it is, but one of the wires should have power to it.

LS6427

iTrader: (2)

I'll check that out. After trying two new MAF's I'm thinking thats all it can be.

If a MAF does fail....then you hook up a new one, the PCM and everything should just work properly again right away, correct??????

Also, isn't it wierd I get no SES light or code when I unplug my MAF on cold start or at any time its warmed up?

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HUNTER02SS

iTrader: (24)

If your MAF is unplugged, then it would throw a code. I think your MAF is working, but when it was tuned, they did not go back and re-set the MAF values back to operating range. I would get your tune checked out.

LS6427

iTrader: (2)

Wow, so do I need a whole tune? If not, what needs to be checked and altered by a tuner?

Can it be fixed using an OBDII scanner? My friend has a "real" one.

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HUNTER02SS

iTrader: (24)

I wouldn't say you need a whole new tune, but there are some MAF tables that are adjusted so they have no affect while tuning the VE table, if this is indeed how it was tuned. You need to have a tuner check out these MAF tables to make sure that they were set back to the proper operating range's.
A scanner is no good for this.

shtnfrds

iTrader: (1)

look in the tune to see what how the maf tables are set, and make sure its not faild/zero at all times causing it to be SD full time.

LS6427

iTrader: (2)

Alright, thanks for all the info man. I'll look into it.

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LS6427

iTrader: (2)

Can a dealership type OBDII scanner at least tell me how these tables are set and if the MAF is ok?

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HUNTER02SS

iTrader: (24)

The dealer's use a TechII, and I am sure they may have something to be able to pull the tune out with.I am not sure if they can make change's though?

LS6427

iTrader: (2)

Its sounding more like a blow-by issue, making my 02 sensors measure things as lean. Then they are making it run rich to try to correct it. Wouldn't blow-by going into the crankcase, then back through for the 02 sensors to read, turn out to be a lean reading?

Then when I tried to reset my PCM by disconnecting the battery for more than 30 minutes, two times with new MAFs, and it didn't work......I think my PCM may be shot.

Shouldn't it reset and bring the new MAF back into play after resetting it. Then if the blow-by is too much for the system, it would at least run with the MAF in the loop for a little while??

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HUNTER02SS

iTrader: (24)

If your car is running so rich that you are getting black soot on the bumper then you could of washed the piston rings. And I re-read your original post and you said you unplugged the MAF 3 years ago, so since then the ECU has relied on your VE table. If your VE table is not correct, which it obviously isn't since it is so rich, then you probably have washed the rings and are getting blow by. BUT you can correct the fueling and get rid of the black soot on the bumper, but until you get the tune checked out, you will not know what is wrong.