Homepage                                                         ^{updated 30-1-2010}

^INTRODUCTION

^{I receive many emails asking whether an owners car need a Mafam or a Synergy 2 tuning box or both.} 

^{If you fit a Synergy 2 you don't need a mafam MF75p as well.  The Mafam MF75p will restore performance to normal but no further. Instead of a MF75p, fitting a Synergy 2 will restore any loss due to the maf sensor and then boost it to new heights. (by around 25%) This is the most popular option and brings the performance up to current levels.}

^{However, to help you decide whether your maf sensor is out of spec, please read this page.}

^{THE MAF SENSOR.}

If your 75 or ZT suffers from poor performance below 18-2000rpm it is most likely due to an out of spec maf sensor. 

This can happen from as low as 30k miles.

The MAF sensor is fitted in the inlet duct on the outlet of the air filter and measures the mass of air flowing into the engine. In theory, therefore, the ecu can inject the correct amount of fuel for the amount air going in and thereby meet the latest emission regulations. Its located on the duct just behind and to the right of the oil filler cap. the connector is obscured by the overlapping top of the air filter housing lid.

In practice, the Bosch sensor is notoriously unreliable and drifts out of spec as it ages. This is understandable, since the sensor element operates at 200^oC and semiconductors deteriorate at these temperatures, even though Bosch seem to have overlooked this fact!

The result is that the ecu most commonly receives a reduced signal, and because it cannot know if the signal is reduced from say a clogged air filter, it must assume it is correct. 

 Moderate but performance-damaging MAF sensor degradation NEVER shows up on standard diagnostic tests.

(Complete Maf failure  - where it is short or open circuit will show up and will also light the engine management light on the dash.)

The maf sensor has most impact at low rpm - below 1800 -2000 where the turbo is not generating much boost pressure. In this 1000-2000rpm range, there isn't a surplus of air and so it is difficult to meet emission regulations without accurately metering the air flow. 

Above 1800rpm, the turbo starts to become effective and there is a surplus of air and so the ecu does not need to rely upon the maf signal as much. It can simply be programmed to limit the maximum amount of fuel and hence torque.

So if the maf signal has fallen due to a degraded sensor, the first and most obvious sign is very sluggish acceleration when pulling away from rest.  This heart stopping delay pulling onto roundabouts and into heavy traffic is downright dangerous.

It also makes the car tedious and unpleasant to drive at speeds below 2000rpm because the fairly sudden fall off of torque requires more gear changing and even the automatic models are just as bad. 

You will also often find that maximum torque occurs at much higher rpm than intended. Possibly not until 2500rpm, whereas on the 75 & ZT it should be around 2000rpm, and on the Freelander, around 1750rpm (thanks to its variable nozzle  turbo)

In about 25% of cases, the signal becomes elevated above normal and this will overfuel the engine at low rpm. Because this doesn't result in poor performance, it is all too easy to assume the maf is working okay. Very poor mpg, exhaust smoke, exhaust reeking of diesel when idling are tell tales of an overfuelling maf.

Note: NO tuning product - boxes, chips or remaps will work properly if your maf sensor is out of spec, so if you are disappointed, having spent £100s on such a product, look to your maf sensor.

Many owners have sold their 75 because they were sick of the poor performance when the cure costs from £57.50!

THE SOLUTION. Follow the steps to find the best answer.

It's hard to diagnose an out of spec maf sensor remotely and there is no hard and fast way of measuring them so I have compiled a list of symptoms to help you decide.

A) First you need to determine if your MAF sensor so bad there is no doubt it needs replacing immediately:

Complete failure is rare - ie zero signal will prevent the engine starting at all :  Usually you will experience other symptoms  I.e. some or all of the following:-

• Very poor throttle response with very slow initial rise in engine revs

• erratic or lumpy idle

• uneven acceleration even above 2000rpm

• the effect of the turbo can hardly be felt

• surging or hesitation 

• juddering and shuddering

• reluctance to rev.

• smokey exhaust 

• NB A very high maf signal from a faulty maf or a short circuit to 5v will overfuel the engine to such an extent that it will stall as soon as you touch the accelerator.

If you conclude it is must be replaced, then you can either:-

i) Fit a replacement Bosch sensor at a cost of around £200 and not rely upon it lasting for more than 40k miles. (if the price paid is much less than £200 check that a GENUINE Bosch maf is being fitted and its not a Bosch type or Bosch compatible one. Dealers are notorious for being economical with the truth as to exactly which maf they are selling you!)

ii) Fit either: A Pierburgh maf and preferably a Synergy 2, or a Pierburgh maf and a Mafam MF75p.

iii) Fit a clone maf off Ebay or a cheap aftermarket one. My advice is don't - they are unreliable and unpredictable. If you fit one of these and still have performance or fuel consumption issues you may be inclined to look for other causes and spend even more money. when all along, it is still a maf issue.

Assuming the maf is not completely useless then:-

B) Which of the following scenarios best describes your car?

1) UNDERFUELLING MAF

• Very poor throttle response with very slow initial rise in engine revs

• Performance below 2000rpm is poor / has recently got worse and the turbo can't be felt until about 2200rpm if at all.

• I have to rev up and slip the clutch to pull onto busy roundabouts or there is a heart-stopping delay before it picks-up.

• When I open the throttle below about 2200rpm, initially there is a moderate response, but most of the remaining travel is not felt to have any effect. 

• As the revs pass 2000-2300 the power starts to come in suddenly and quite strongly in comparison to lower rpm. (all or nothing effect)

• The engine is very reluctant to rev over 3500rpm even in first gear.

• If I unplug the maf connector, the low down torque is much better, though at higher revs it may be worse.

• My 50-70 time in top gear is well over what it should be.

• I am disappointed with the results of having a remap/chip/tuning box fitted, especially below 2000rpm.

• Fuel consumption has fallen somewhat. 

• My auto stalls easily when pulling away.

RECOMMENDATION: FIT A MF 75p or Synergy 2 but be prepared to fit a Pierburgh maf as well - sooner or later.

2) OVERFUELLING MAF. A very high maf signal from a faulty maf or short circuit to 5v will overfuell the engine to such an extent that it will stall as soon as you touch the accelerator.

• Performance below 2000rpm very good  - the car is very flexible and responsive

• Fuel consumption is poor or appalling

• When I open the throttle, there is a delay, then a puff of smoke and then the car accelerates. 

• The exhaust smells of diesel when idling

• Idling is lumpy or uneven and fluctuates up and down

• If I unplug the maf connector, the performance is about the same or a bit worse.

• In extreme cases, as soon as I touch the accelerator the engine chokes and stalls, with a cloud of black/grey smoke smelling of diesel

RECOMMENDATION: PIERBURGH MAF AND SYNERGY 2 (You must change the maf sensor as well - a Synergy 2 will make the symptoms caused by an overfuelling maf worse)

3) MAF OKAY

• Performance below 2000rpm is the same as ever

• Fuel consumption is normal

• I can just feel the turbo from around 1800-2000rpm

• My 50-70 in top time is about 9.5-10.5 seconds, (75/ZT)

• However, the engine doesn't really want to rev past 3500rpm except in 1st gear.

• I want much better overall performance from below 1500rpm to over 4000rpm

RECOMMENDATION FIT A SYNERGY 2 (FOR A MORE FUTUREPROOF SOLUTION  - your maf can only get worse!)

PIERBURGH MAF AND SYNERGY2 ARE ON SALE IN THE TUNING-DIESELS ONLINE SHOP

FOOTNOTE: 27-1-06 SOME MAF TESTS.

I did some comparisons of a dead maf kindly donated by an owner, my good maf and a Pierburgh Maf.

The readings were obtained via the diag socket using my ACR4.

The dead maf also had an open circuit IAT sensor so the ecu defaulted to 8C.

The Pierbugh maf needs a Mafam, as stated on my Mafam pages, it also has an incompatible IAT sensor that the ecu reads as 73C! Another reason why it needs a Mafam with an IAT - i.e. the MF1P. 

The dead maf is clearly useless, with no IAT and a signal that drops off above 3000 even a Mafam won't be much use. Normally they don't go out of spec so drastically.