Intermittent MAF fault

[fredfelcher 0]

Hi guys,

 

I'm having an intermittent MAF fault:

 

 

00553 - Mass Air Flow Sensor (G70)

28-10 - Short to B+ (intermittent)

 

Interestingly this only happens when I give it some welly, not if I pootle about (which is NOT what I want to do in a VR6...)

 

It's an OBD2 in a Mk2 Golf (sorry it's not a C :( ). I've cleaned the MAF then tried two other known good MAFs without any luck. I've checked the wiring at the plug (even taken out the pins with a special tool I bought) and found the insulation had slightly split. Wrapped them properly in insulating tape but same as before.

 

On VAGCOM the airflow values look OK from idle and normal driving. They do shoot up to about 160g/s at full throttle but don't know if this is right or not?

 

The car is well modified - BMC CAI, Dubpower manifold, Magnex with cat bypass and was rolling roaded at 200bhp BEFORE the manifold was put on. I'm wondering if the airflow at high throttle is now somehow too much for the MAF and causing a fault?

 

I can really feel the difference - before I boot it to induce the fault, the low down power is smooth and steady; after it is slightly hesitant just off idle and some minor bucking. Nothing terrible and still great at anything over about 1500rpm, but just not quite right lower down.

 

If anyone has any thoughts or ideas I'd be grateful before I go and get another MAF for $$$

 

Cheers!

[buttles 0]

Found this the other day. http://s2central.net/ds_G70.html. Maybe a guide to the OBD 2 MAF in there somewhere?

[Kevin Bacon 5]

Yeah I used to get that on my OBD2 Supercharged and Turbocharged.

 

Never did get to the bottom of it and was one of a few reasons why I binned off Motronic and went standalone, LOL!

 

B+ if I remember right is the positive track from the fuseboard that is only active during cranking and when the engine is running. A short to that is usually a phyiscal short in the loom or when the MAF output exceeds 5V, which is unlikely in a normally aspirated VR6 but what you could do is tape a voltmeter to your screen and connect it across ground and the MAF signal wire, then go out and give it death. See what voltages you get. Normally around 1.2V at idle, rising to 2 - 2.5 in the midrange... shouldn't really go over 3.5-4 on your motor.

 

When you get this short to B+, does the motor hiccup?

 

Has yours been remapped?

 

If all else fails give Vince at Stealth a call, he's quite well experienced in this problem :D

[fredfelcher 0]

Thanks for the replies guys. I looked at the page Buttles but unfortunately nothing relevant there (over the last couple of weeks I reckon I've looked at every page Google can find on VR6 MAFs and G70 sensors...)

 

Kev, that's interesting info about the problem with FI. I think it may have coincided with fitting the CAI - perhaps that's just a tiny bit too much extra airflow...!

 

I've been trying to avoid looking through the loom for a short, but at some point I'll have to get my hands dirty. I'll give the voltmeter idea a go first.

 

I don't feel the engine 'hiccup' as such, just the low rpm smoothness not there any more when picking up from low speed (eg 15mph in 3rd, 25mph in 5th) which is there when I clear the code.

 

It's not been remapped yet. I've got some 268s and a VGI to go on before that. I need to get an OBD2 throttle body adapter from Stealth anyway since my manifold's OBD1 from my old car so perhaps I can pick Vince's brains then - never met the guy, will it be like meeting God or something...? My only reservation is that he'll probably persuade me I need one of his lovely turbo kits (and I don't need much persuading!!) - that'll be more saving up then!

 

Cheers for your time fellas