In trying to figure my car out I disconnected the MAF sensor. Wala, no the car doesn't hunt around for idle and die...

But there were two things I saw in the arcs that have me wondering.

One is the statement that when the MAF sensor is disconnected the car doesn't go into closed loop mode. I found that not to be true as the car goes right into CL correctly.

The other thing that's odd to me is that my scanner is showing gps data even though the MAF is disconencted. I'm guessing this is the ECM estimate of air flow. If so, I'd be nice if the scanner would show an actual measurment rather than what the ECM thinks it is.

Sorry if this commonly know stuff. I've just slept.

 

The maf is not one of the requirments for closed loop so with it disconnected it going into closed loop is normal.

When the maf is disconnected the gps should show a reading of 0. Some ecms have a display for both actual and calculated. There may be another display for maf or the scanner may be reading the wrong one.

 

I just went to lunch and reconnected the MAF sensor because I'm starting to get tired of the hesitation with throttle.

So, as usual with the MAF hooked up the ECM declared a lean condition after a few minutes of driving (actually happens while stopped at a light). I looked at the BLM and Intergrator and they both zeroed out (128) where before they seem to run around 150 or so.

While I was out I picked up a new O2 sensor since mine may have been affected by my FPR going bad. I'll post back with results later.

 

If the MAF is disconnected while the engine is running, the last "read" GPS will be locked in for use.

If disconnected before starting, then it should default to 255.

Your problem sounds like a bad MAF, especially with the "lean" (which is probably false) reading.

 

In reading the ARCs I came across a caution that stated just because the lean condition goes away when the MAF is disconnected doesn't mean that the MAF is bad. I did try the "whack it with a screwdriver" test and the car ran better but what exactly does whacking do to get it to work correctly for a few minutes?

I'd also like to see if the burn off module is working but how do I check? Have someone shut the car off while I watch the wire and see if it glows for a few seconds?

 

Well, I slapped my old MAF on this evening and my integrator went from 150-165 down to 130-150. The BLM is still up there around 150s.

I'm gonna see what it does in the morning after it sits.

 

I'm not sure what tapping on the MAF does, other than increase the chance of breaking it

But here would be my course of action...

Unplug the battery to reset the ECM, and change the O2 sensor at the same time, if in fact it was a false lean, then you may have washed the O2 down and it's not sensing correctly.

When my MAF took a dump, my engine started to run rough, to the point it would hardly start...unplug the MAF and it fired up fine.

My only code was a 44, so I plugged in the scanner, fired up the motor and watched the 02's dive to like 20mv's, all the while the engine is running richer and richer...basically the MAF was causing it to dump too much fuel and flood the O2 sensor, so it could not read correctly.

After resetting the ECM and replacing the MAF, I still had a little surge in the engine, so I replaced the O2 sensor, reset the ECM again, and all's been fine.

Hope this helps.

 

Do forget that the o2 only measures oxygen. It doesnt measure a/f ration. If you have a rich misfire none of the oxygen is used up so the o2 sees lots of oxygen and says it lean. The ecm in turn dumps more fuel making the condition worse. A maf failure could cause the the engine to run rich and throw a lean o2 code.

 

It's been the weekend of playing. I've replaced the o2 sensor and threw in some new plugs.

I can say the car does run better, however, small children and forest creatures still pass out as I drive by. The car still seems to be running rich. The Intergrator is now around 130-140 but the BLM is right around 155.

As far as the MAF, it would seem that there should be a calculation that one can do to check if it's working properly. i.e... a 305cid engine running at 2K RPM should flow Xgps. If I had plenty of money I'd just by another MAF and throw it on but since it's the most expensive suspected part, I'm saving it for last.

The A.I.R. diverter seems to be operating correctly.

This might be a crazy question, but could "too free flowing" exhaust cause this? I'm thinkning not b/c my O2 is pretty far up stream (stock location).

Does the PROM have any effect on what values are stored for the BLM? I think I'm going to pull the Hypertech chip out and see if the factory chip will bring the BLM down.