air flow meter

[GIXXERUK 0]

i had my car at stealth today and it ran about 180bhp and 189.6 lb ft of torque

the vagcom was clear but vince reckons he saw a glitch somewhere that suggests the MAF is the problem, he said vagcom will only pick the MAF up if its dead and wont report if its just not running correctly

 

is there a way i can test the MAF ? the car does seem excessively thirsty on the juice, i did approx 300 miles on £60 worth of petrol today

 

otherwise the car runs fine and idles fine but it seems to have changed a little recently with most of the grunt being at the bottom of pedal ?

 

any ideas

i would obviously go for a 2nd hand MAF as they will be stupidly overpriced at the stealers so being able to test it would be useful

 

tia

[GIXXERUK 0]

c'mon people

[dr_mat 0]

300 miles on £60 is not that bad ... Particularly as you're counting the RR session in the middle, no?

What's the MFA saying for mpg overall?

Weirdo thing is you're showing good torque, and poor bhp. What's your torque curve/power curves look like?

[GIXXERUK 0]

dr_mat, i've posted them here

http://the-corrado.net/.archive/forum/viewtopic. ... 298#373298

 

the MFA usually reads 23-25 mpg (unless i'm going down hill)

yes the torque is a reasonable figure but the bhp is well down

[JT 0]

not sure if this is of any help but why not see how much it is from bosch direct (no mark up and all that) just vw corrado and year made and will find your car eventually?

 

http://ecat-online.bosch.de/toc/en/Etv5 ... vaDisabled

[GIXXERUK 0]

JT-G60, cheers mate i'll take a look

 

i just wonder how nuch the mfa could affect the bhp without really altering the general running of the car and show no fault, i know the mfa is a common fault and i wanted to know is it possible to test it (which i doubt, test to see if its working ,maybe, working correctly not likely)

[dr_mat 0]

Careful now, you don't wanna go suggesting Vince is fallible round here, they'll tar and feather you before kicking you out of town .. :)

Comments in other thread...

[chrishill 0]

300 miles to £60 worth of petrol sounds about right to me, its about what i get... then again theres nothing to say my MAF isnt dodgy too! :lol:

[GIXXERUK 0]

dr_mat, everyone is fallible and vince was on a tight schedule and the maf was an off the cuff remark but he did justify this by noticing a glitch when the car was under load

he said it is working but maybe not correctly, hence vagcom not reporting it as a fault

 

shame there isnt someone close by who i could swop my maf with to try it , the nearest is dazzyvr6

[GIXXERUK 0]

MAF Sensors (Bosch Style)

The Bosch style system is used on 5.0L and 5.7L Firebirds, Camaros and Corvettes, most European cars and some Asian imports. This design of sensor uses an exposed platinum sensing wire and a "burn-off" feature that uses a relay to burn away impurities off of the hot wire (figure 3).

 

Diagnosing Contaminated Mass Airflow Sensors

MAF sensors can get contaminated from a variety of sources - dirt, oil, silicone, spider webs, potting compound from the sensor element itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the MAF overestimates airflow at idle (causes the fuel system to go rich) and underestimates airflow at high airflow (causes the fuel system to go lean). This means that Long Term Fuel Trim will learn lean (negative) corrections at idle and rich (positive) corrections at higher airflow. If a vehicle is driven at WOT (Wide-Open Throttle) or high loads, the fuel system normally goes open loop with a rich mixture to provide maximum power.

 

Real World Example: 1993 Buick Century 3.3 Liter

 

1993 Buick Century Wagon

 

This vehicle was booked in for diagnostics following a customer complaint. The repair shop had replaced the catalytic converter, but this had not corrected the high NOx emissions.

 

The first clue this was a lean air/fuel ratio problem was the final test result, which was very similar to the retest result of .1056 g/km [0.17 g/mi] HC, 1.6447 g/km [2. 65 g/mi] of carbon monoxide and 2.5314 g/km [4.08 g/mi] of NOx. The clue here is that the NOx was actually higher than the carbon monoxide!

 

The second clue was the Diagnostic Trace Report (figure 4). If you look at the sections of the driving trace where accelerations occur, you will see the NOx goes high and carbon monoxide remains low. This is just the opposite of what you should expect! There will usually be some degree of enrichment and high carbon monoxide during accelerations to improve throttle response and reduce NOx emissions.

 

The third clue was Long Term Fuel Trim (LTFT) at high idle. I hooked up my scanner and checked fuel trim and airflow at exactly 2500 RPM while also observing the O2 sensor on my lab scope. I noted the indicated airflow for future reference, which was 14.1 g/second.

 

The scope showed the vehicle was maintaining closed loop, but the scanner indicated the control system was compensating for an under-prediction in airflow or a lean condition. This would serve as a baseline test to see if things improved after cleaning the sensor.

 

At this point, it was time to stop checking and start repairing. Removing the MAF sensor on the Buick is easy. Just remove three screws and the sensor module is in your hand. A close visual inspection showed there was a fuzzy build-up on the sensing element. This required a bit of scrubbing with a soft toothbrush and some throttle body cleaner. Just spraying the sensor wire did not remove the fuzzy build-up that appeared to be small fibers from the air filter. I followed this with some brake cleaner and compressed air to make sure there was no residue on the sensor that would attract more dirt.

 

With the sensor module reinstalled, it was time to see if the cleaning improved the transfer function of the sensor. Reproducing the test conditions from my baseline, I took the RPM to exactly 2500 again. The indicated airflow was 17.6 g/second, an increase of almost 25 percent.

 

The long-term fuel trim values were now close to the nominal 128 value with a reading of 124. A second test at the Technical Center confirmed the NOx had been reduced by 40 percent and the vehicle fast-passed when taken through the inspection lanes for an official I/M240 test.

[Lippy 0]

300 miles on 60 quid bloody hell

 

i stuck 45 quid in mine did 240 miles and still have 1/2 tank left!

 

hope you get sorted gixxer, like you've said dont throw money at the wrong diagnosis!

 

Andrew

[GIXXERUK 0]

Lippy, nice to meet you yesterday andy ..... i'm hunting the problem down like a dog now :-)

 

£318.71 for a new maf from vw :shock: :shock: , i could buy a vr for that off ebay :wink:

[Lippy 0]

gixxer hasnt KevHayWire just got shut of one - has he got a spare?? just a thought...

[GIXXERUK 0]

Lippy, aye i spoke to kev :-( just missed it

[Lippy 0]

arse!

[corradophil 3]

i did approx 300 miles on £60 worth of petrol today

 

Ooh, finally something to make me glad I have a valver and not a VR. Mine does over 400 miles on £50.

 

Not sure on VR6s, but I know on a 20 vt you can measure the airflow reading the maf is putting out in grams/second using vag-com, which can give a good indication if something is wrong. I'm sure someone on here can confirm or dismiss this.

[GIXXERUK 0]

£150 exchange seems to be the price from a bosch dealer, better than £318 from the stealer for the same thing

[joebloggsVR69 0]

I get about 240 miles max on £55 of petrol

Works out to around 20 mpg :oops:

 

But I drive on congested london roads, averaging about 12mph!

[GIXXERUK 0]

nice to see some figures , good comparison , so the fuel consumption is ok , runs and idles fine, even right up to the red line :-) torque is fine but its showing low bhp ? i'm not too sure of the symptoms of the maf :-(

[Supercharged 2]

I wouldn't say 300 miles from £60 is ok for a VR!!

 

They should make good economy - near to 35mpg on a long run but obviously depends on driving style...

 

MAFs - best bet for early ones is BOSCH dealer exchange...

[GIXXERUK 0]

Supercharged, cheers , bosch dealers are quoting £150 +vat exchange and non returnable

[Kevin Bacon 5]

Not sure on VR6s, but I know on a 20 vt you can measure the airflow reading the maf is putting out in grams/second using vag-com, which can give a good indication if something is wrong. I'm sure someone on here can confirm or dismiss this.

 

Unfortunately you can't do that with OBD1 (all Corrado VR6), the ECU doesn't support it.

[VRTrickster 0]

Ive seen replacement maf listed at GSF for about 50 quid!(PIERBERG) And also a SIEMENS .Has anyone brought one of these as i have always wondered about them?

[Supercharged 2]

They are mk4...

[VRTrickster 0]

Oh! I did type in corrado oh well !! :oops: