maf reading--?

[Lee Thompson]

New to DS, through the 1/4 mile run I have 3 somewhat equally spaced spot where my MAF goes from 255 to 33 for one fram. Anyone else ever see this and what does it mean or the cause? All other reading are normal. I tried another MAF. Same thing.Thanks

 

[bruce]

It's called MAF drop out.
The only total cure is using a Translator, with extender chip, or MAFless ME. With a Translator, you can still see the code error happen, but it's not really there.

There's some alledged fixes around, but the problem is two fold, part in the code and part in the ecm.

In extreme cases you can see the injector line spike, and even see it in the O2 voltage line.

In some cars you can feel them stutter when it happens, others you can't.

 

[Steve Y]

The regular ME is, and always has been immune to this problem as well.

Bruce, I a little confused. Fill me in on the code error. I can't see where the drop out is caused by anything to do with the ecm.
I see where John Spinas testing with a leaf blower shows where the power regulator in the MAF peters out when alot of current is called for....which drops out the readings.....
It appears to me the ecm just reports whatever signal it recieves from the airmeter.

As far as believing the DS reading...look up at the PW and see if that follows the airmeter. I suspect you need to be in the fastest update mode though.

I see too many glitches happen with DS to be comfortable with it. It seems most of the time it happens at high load where the plug wires throw off the most radiation.

Steve

 

[bruce]

Swing by sometime, and I'll fire up the ecm bench and show ya whats going on. You can watch the injectors/LEDs drop out, in some cases. Being able to watch the outputs, takes DS completely out of the picture. Thou, if you watch both you can see the MAF drop out synchs with an injector's miss.

 

[Steve Y]

Hummm. I didn't think the MAF logic would allow it to go past 6FF or whatever it is. I don't have the book with me. From 6F8 up to that point it is FF'd so that confuses me.
Are you force-feeding the maf input with a signal generator or a turbocharged leaf blower and a maf? LOL
Steve

 

[bruce]

Originally posted by Steve Y
Hummm. I didn't think the MAF logic would allow it to go past 6FF or whatever it is. I don't have the book with me. From 6F8 up to that point it is FF'd so that confuses me.
Are you force-feeding the maf input with a signal generator or a turbocharged leaf blower and a maf? LOL
Steve

I have Doc run across a set of micro switchs, tied to a bunch of astable 555s. Then a series of retired ASA high speed Morse Code Interceptors, that convert that into braille for the MAF input to the ecm. Works slick til Doc gets tired. usually about 3-4 passes a day is his limit.