MAF Test Range

[bcameron70]

Hey there, I want to check my MAF for proper range to make sure it is still operating properly. Does anyone know where I can get the OHM reading range for the OEM Bosh unit? Which pins to test across? Thanks

[Disco Mike]

Download the Free Rave Cd from the link in my signature section.

[bcameron70]

Cool, I had the Rave, but did not know it was in there, should have RTFM first! Thanks Mike!

[Disco Mike]

By the way, why are you wanting to test the MAF, do you have fault codes what are the exact fault code numbers.

[bcameron70]

I do not have the fault codes yet, but I'll grab them this morning.

Bought my DII with 168K...did a bunch of rehab work to it

Last spring I changed out the o2 sensors (front and rear), plug and wires...ran pretty good (no stuttering) for a while but has always smelled like it was running rich.
Changed the coil packs, injectors, fuel pump ...

Never had a disco II before, but I would think it would have a little more power than it has for a 4L

This fall both front o2 sensors failed (with codes) again, changed them out under ATL/BR warranty, but they can't be the issue. Had a bunch of misfires due to dumping of fuel when the o2 sensors failed.

Ran OK (still not much power) for a couple months and now engine burning real rich again (I can smell it) and she is starting to stutter a little. want to fix before I have to pull more o2 sensors as they are not fun and are a symptom of the larger issue.

I have changed the air filter and I have inspected for intake leaks after the MAF.

I'll go pull codes, but they were clear after i finished the last o2 sensors, I would suspect some misfires and o2 sensor failure again.

What does your gut say? Thanks Mike!
-Ben

[Disco Mike]

If you want some help with it, send me your number then go get the codes read. I will call you once you have the codes and I have your number.

[Savannah Buzz]

Here's some pages for the RAVE to consider. Shows text for the MAF and IAT sensors (two for 1 today), and cable pin outs.

The cable runs to the ECU, and here's what's on each pin, from Engine Management section of the RAVE:

1 - to ECU 34 - IAT signal, 0-5 volts
2 - to + battery volts when main relay "wakes up" the engine
3 - to ECU 9 - MAF earth ground
4 - to ECU 7 - MAF 5 volt regulated power (runs the MAF)
5 - to ECU 23 - MAF signal 0-5 volts

Now an important lesson can be gleaned from the text. The MAF heats up part of the sensor to 360 F plus ambient temp. So on a 100 F day under the hood, that's like 450 F. Spray that with a can of CRC MAF cleaner, even though it is formulated for cleaning an MAF, and you are asking for problems. Likewise, a good gulp of cold creekwater might have a similar issue. MAFs should only be cleaned when cold, and the cleaner is approximately the same temp.

[bcameron70]

Thank you Savanah for the info, I still plan to check out the MAF and I appreciate the direct Pages.

Mike, here are the codes, and just as expected (lol)
PO150 (O2 sensor circuit malfunction (bank 2, sensor 1) ) ((Is this the cause of the fuel dump?)
PO172 system too lean (bank1)
PO175 system too lean (bank2)
PO300
PO302
PO304
PO306
PO308 (Whole passenger side of engine misfiring, but I make it up hills ok)
PO455 (Not sure of this guy)
P1300 (multiple misfire)
P1590 (ABS, but I know that one)

She smells of dumping fuel out the pipe now, but even when she was running half descent (still not the power I expected out of this unit) she smelled like fuel dumping out and this is before I touched the injectors or coild.

Mike, I'll message you my Phone number, and I'll keep the board up with the findings as we go. This vehicls is not rocket science as I have found so far, however just seems a sensor is off or wire is grounded somewhere providing a fasle reasing.

Here is another note, my tach goes up to 2K when started and back to 0 when stopped....that is just the gauge of course and I have cleaned all of my alternator connex on the unit itself and I am getting good juice to a new battery. Now and then on a cold day (I am in Midcoast Maine) the tach will start to magically work until I get warm and then back to 2K....I have also cleaned the ground harness straps to the chasis of the vehicle.

[bcameron70]

Hey there Mike, Thank you for the time on the phone today, I appreciate all of the advice!

I ordered the timing chain kit from AB for next weekends project.

Can you send me or post the other recommendations on engine cleaning we discussed. You had mentioned a product that goes into the throttle body as well as a fuel additive to get the gunk out after my Chain goes in. Thanks!!

[Savannah Buzz]

May be that was SeaFoam, but while it goes in the tank, it is sucked into the intake manifold via a vacuum line, you would want to uses a spray cleaner for the throttle body itself that is made for that purpose.

If doing a timing chain you may want to inspect your oil pump, or do a pressure test, they can crack and still pump at reduced pressure. And be sure to prime oil pump before re-assembly.