Is my MAF farked

[philws]

G'day all

The Trol: GU III ZD30
EGR Block
Dawes and needle valve
Catch Can

A little while ago I posted about some error codes I was getting

- 0406
INT/AIR volume (excessively high signal from Mass Air Flow Sensor)
Air Duct, Charge Air cooler, Variable Nozzle Turbo Charger Control System,
Variable Nozzle Turbo Charger, Mass Air Flow Sensor failure, Circuit malfunction
- 0905
Turbo Pressure
Circuit malfunction, Charge Air Pressure Sensor failure

What I noticed after that is that my EGTs were down heaps, the car was driving like normal except that at the top of the rev range it had less power, from about 2800 to 4000 or so.

One day after work the check engine light went out and the car was pretty much back to normal but the EGTs are quite high especially on the freeway.

My thought at the moment is that the car has always been running a little rich (EGTs have always been higher than I would like and fuel use has been a little high as well) I think that whatever is faulty, ?MAF maybe, went all the way out which forced the ECU to use a leaner mix and then a richer mix when the ?MAF went back to semi-normal - did any of that make sense? Could this be possible and what are the sensor that would give the above codes? is there anything else in the system that governs fuel mix.

Also I have cleaned the MAF with no effect, it didn't make the car run any different when I did it, it was a couple of days later that the check engine light went out. Another curly one is that my tacho has died, it happened after the initial check engine light came on and started as the needle jumping all over the place and now it has just flat-lined.

Cheers Heaps

Phil

[boots]

Hi philws , have read on the forum about disconnecting your battery for 24 hours to clear fault codes properly , not sure if this wil help you or not . some heavy machinary that I've operated if the tacho goes the alternators shot or wiring at the alternator is loose or faulty . maybe check your charge rates to see if yours is ok . worth a look anyway . goodluck .

[philws]

I have checked the MAF voltages as per YNOTs (http://www.nissanpatrol.com.au/forums/showthread.php?597-Checking-and-cleaning-MAF-sensors) instructions. I found that the red wire is reading 2.15 volts and YNOTs spec say it should be between 1.6 -2.0, is .15 volts going to be enough of a difference to cause issues? both the whites are within spec. Also does anyone know where the tacho gets its input from? trying to fault find on that atm.

Cheers

Phil

[Chaz]

I have checked the MAF voltages as per YNOTs (http://www.nissanpatrol.com.au/forums/showthread.php?597-Checking-and-cleaning-MAF-sensors) instructions. I found that the red wire is reading 2.15 volts and YNOTs spec say it should be between 1.6 -2.0, is .15 volts going to be enough of a difference to cause issues? both the whites are within spec. Also does anyone know where the tacho gets its input from? trying to fault find on that atm.

Cheers

Phil

Phil,

Your MAF voltage at idle will be a bit higher due to the EGR being blocked. 2.15 is normal for an engine with blocked EGR and is still ok. It may cause a warm engine to idle slightly richer, but shouldn't increase fuelling under load.

The tacho is driven from the ECU with signals from the crank angle sensor, which could well be the problem. Fuel mixture is determined by signals from the MAF, Throttle position sensor (TPS) and crank angle sensor (rpm).

[philws]

Hi Chaz,

Thanks for the info, so it sounds like the crank angle sensor could be the problem as it contributes to both symptoms...?

Where abouts is it located, is it possible to test for output current from the sensor with the car idling? also would it generate the 0406 and 0905 codes?

Thanks heaps for all the help

[Chaz]

Phil,

The crank angle sensor is located at the front of the engine, just above the main crank pulley and slightly to the driver’s side. It gets plugged intro the ECU and pulses voltage like a hall generator which should increase voltage as rpm increases. The can fail if they get too dirty or become loose against the engine.

The crank angle sensor won’t give you those codes. They are most likely a result of the MAF and MAP voltages being out of sync. This can either be a faulty MAF or a leak in the intake system somewhere. Also, you’re boost may be set too low or too high, or the spool rate too aggressive. Even a faulty plug or wiring to the boost control solenoid could give you those codes.