Is my MAF goosed?

[KugaWestie]

I am approaching the end of a full body off refurbishment and have just restarted the engine and bedded in a new cam last night, but when the engine was warm a throttle blip would make it die immediately.

Tonight I connected up RoverGauge and checked the TPS. As you can see from below TPS was showing 11% in the closed position. My understanding is the ideal is 5%.




I ran an error code check and sure enough throttle pot was showing as an error.




So I adjusted the TPS as far as I could and then got these readings as below. 6% closed and 94% open, which I think is pretty close to being ideal.






When trying to start the engine after completing the above it would catch and die immediately.

Edited by KugaWestie on Wednesday 15th June 20:30

[KugaWestie]

So I then decided to disconnect the MAF, and the engine fired up immediately and idled fine.

I ran another error code check and got this



As soon as I plugged the MAF back on, the engine died.

So do you think the MAF is the problem?

[KugaWestie]

It’s a 1995 4.0 Serp engine

[Italian450]

I had a similar problem after changing my injectors.
Engine started but stuttered and would not accelerate / rev.

Unplugged the MAF and all was better in limp mode !
Changed out the MAF and all went back to normal.

Good idea if you can make a test with a known good meter.

[KugaWestie]

Zener said:

Fuel temp is a concern are you sure you have not reversed the two plugs coolant sensor and inj rail sensor ? although they seem to indictate similar temp so something is up regardless

The screen shots where you can see those temps are all before an engine start, so you would expect to see the same temps surely. Plus the back of my garage (where the back of the car is) is warmer than the front due getting the sun on the door so makes sense to me.

I am pretty sure I have them the right way round, but any guidance on how I can confirm this would be appreciated

Edited by KugaWestie on Friday 17th June 11:32

[KugaWestie]

Italian450 said:

I had a similar problem after changing my injectors.
Engine started but stuttered and would not accelerate / rev.

Unplugged the MAF and all was better in limp mode !
Changed out the MAF and all went back to normal.

Good idea if you can make a test with a known good meter.

Thanks, that's reassuring as it supports my theory

[Italian450]

Here is a page coming from Mark at Blitz racing see the part on AFM testing etc.

http://www.g33.co.uk/pages/technical_fuel_injectio...

It may help

[KugaWestie]

Here is a screen shot of rover gauge with the engine running, absolutely no activity on the MAF, so I think it is knackered.

[Steve_D]

KugaWestie said:

Here is a screen shot of rover gauge with the engine running, absolutely no activity on the MAF, so I think it is knackered.

Before condemning it completely have a good look at the connector. It gets very crispy around there and I have seen both broken wires and pins pushed back in the connector so worth taking a very close look.

Steve

ETA where in the UK are you? Another owner or a workshop may be able to offer a known good one to test.

Edited by Steve_D on Thursday 16th June 21:18

[NMNeil]

It seems it uses a hot wire sensor, and over time they get deposits build up on the wire, Fords were prone to it, but they could easily removed and cleaned, no idea how easy it is to remove on your car though.

[blaze_away]

KugaWestie said:

Here is a screen shot of rover gauge with the engine running, absolutely no activity on the MAF, so I think it is knackered.

Try that againbut with MAF set to Direct. It always gives higher readings if I remember correctly.

Also...to clean the maf sensor. Take it off the car. Remove the 2 end plates ofthe maf. You will then be able to see the sensors hanging down in a small aperture to the side of the main aperture. Squirt brake cleaner in thete and soak the sensors. (DO NOT TOUCH THEM) Keep squirting a few times until they look cleaner. Reassemble and test again

[KugaWestie]

Is there a way to check the MAF on the bench rather than in the car?

[Steve_D]

Have a read here.
http://www.g33.co.uk/pages/technical-fuel-injectio...

Steve

[blitzracing]

You need direct mode. You can check the standby voltage with a meter to show it's actually giving a voltage.Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).

Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts after the initial "warm up" spike. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct

[TVR450s]

Afternoon

Does anyone know of these can be repaired or o/hauled in the UK? It seems criminal to condemn them all as their relatively simple if not unreliable components.




All failed the AFM voltage output test.

Thanks.

[KugaWestie]

blitzracing said:

You need direct mode. You can check the standby voltage with a meter to show it's actually giving a voltage.Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).

Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts after the initial "warm up" spike. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct

It overshoots as described so I think it’s dead. I have managed to find a Jag replacement that is on its way so hopefully that will solve it

[KugaWestie]

Just to close this one out, My Jag replacement MAF arrived, so I fitted it on the car and started the engine. It settled to a nice tick over straight away. A blip of the throttle and it responds instantly, so problem solved.

Can the MAF’s be repaired?

[blitzracing]

TVR450s said:

Afternoon

Does anyone know of these can be repaired or o/hauled in the UK? It seems criminal to condemn them all as their relatively simple if not unreliable components.




All failed the AFM voltage output test.

Thanks.

I've pulled a few to bits. The electronics is pretty simple but the hot wire sensor wires are spot welded to the PCB and have to be cut to remove the PCB and dont solder back well however I would be interested if having a go repairing them if the alternative is scrap ? Drop me a PM if you are interested.

[mezzogio]

KugaWestie said:

My Jag replacement MAF arrived, so I fitted it on the car and started the engine. It settled to a nice tick over straight away. A blip of the throttle and it responds instantly, so problem solved.

Hi
Can you please give us the reference of the jaguar MAP you ordered?
Regards

[KugaWestie]

mezzogio said:

Hi
Can you please give us the reference of the jaguar MAP you ordered?
Regards

I found a second hand one removed from a 4.0 1992 XJS. Part code was 5AM200950