Hi all,

I have spent the last few weeks reading every post, article, tech bulletin I can about this subject and I still have some unanswered questions. I'm hoping you can help.

I'll try to keep the back-story brief but informative/useful:

• Bought car about 3 months ago and it was very sluggish, no low end torque
• I bought a tuning box which helped a little but I realised that there was a bigger problem.
• Did EGR bypass, replaced air-filter (with Pipercross oiled filter) & crank-case breather
• Replaced all hoses with silicone ones
• for a few days the car was like a new machine. Ran really well, pulled like a train.
• Then... I got the common "lack of power below 2000rpm" problem

After doing some reading I diagnosed it as the MAF (assuming due to oil from the new air filter) and disconnected it. There was an immediate improvement.

I took the car into my local land rover specialist and they confirmed my diagnosis and sold me a new MAF (ouch) I fitted it and there was no improvement at all.

My question is this:

Does disconnecting the MAF really help you to determine that the MAF is the source of the problem? If unplugging it simply forces the ECU to use default values then surely it could be a different sensor which is causing the problem.

I've read a lot about the various sensors and so far I can see two others which could cause my problem..

1. Air temp sensor on intercooler hose. (I changed my hoses so perhaps I damaged something) Also since removing the EGR I imagine that any black gunk that made it into into the air box has been blown all over the sensor. There certainly is some black oily stuff inside the hoses.

2. The Fuel rail pressure sensor. I hear that these (or the harnesses) often fail. (I fitted a tuning box so like sensor above I could have damaged something) I don't think I did because it did initially work fine. I looked at the green clip on the harness earlier and it was very oily (I took it for a drive once without the engine cover on and sprayed oil all over the place) I've cleaned this as best I can but it's made no difference.

So I guess I want your advice on what to do next.. it could just be a duff MAF or an incompatible one. I might be barking up the wrong tree..

I have it booked to go back to the LR specialist on the 20th and they might spend hours on it (costing me a fortune) so I thought it might be worth trying something myself first.

I'm thinking about replacing the air temp sensor (as it's cheaper) and cleaning out the inlet/airbox to get rid of any black slime.

If this makes no difference I can tell them I did it and let them focus on the MAF and fuel pressure sensor.

If you've made it this far thanks for reading!
Dave

Change the air filter back to a standard one for starters. The pipercross oil can mess up the MAF. I know Rover Ron recommends them.

The MAF you were supplied with- is it a Bosch one? Some of the cheaper ones are not worth it.

hi

if youve got problems disconnect the ron box as it will only make ur problems worse

as above what maf did u get and personally would change the air filter back as mentioned

plus when was the fuel filter pump etc replaced last and a service done

is the vcu brakes ok and not binding in any way

have u checked ur vacuum hoses for splits etc, is the inlet manifold very dirty

ref to the maf make sure its a genuine bosch one or if u get a pierburgh maf it is used in conjunction with the ron box as it has a built in compensator, some of the cheap bosch mags dont have it built in and therefore can cause all sorts of trouble

better to start by turning the box off so u can then start without any modifications , have u git access to a compliant diagnostic reader

if u do a search through here and on rover on website it will help by giving u some guidance

let us know how u get on plse

gstuart said:

hi

if youve got problems disconnect the ron box as it will only make ur problems worse

as above what maf did u get and personally would change the air filter back as mentioned

plus when was the fuel filter pump etc replaced last and a service done

is the vcu brakes ok and not binding in any way

have u checked ur vacuum hoses for splits etc, is the inlet manifold very dirty

ref to the maf make sure its a genuine bosch one or if u get a pierburgh maf it is used in conjunction with the ron box as it has a built in compensator, some of the cheap bosch mags dont have it built in and therefore can cause all sorts of trouble

better to start by turning the box off so u can then start without any modifications , have u git access to a compliant diagnostic reader

if u do a search through here and on rover on website it will help by giving u some guidance

let us know how u get on plse

Click to expand...

Hi thanks for the replies,
The MAF was not a Bosch one I believe it was Allmakes 4X4 the garage charged me about £90+VAT for it. It came with the housing as well. Not just the sensor.

The tuning box is not a Ronbox it's a Diesel Express one. I have had it turned off since the sensor problem started so it is not that which is causing the trouble. Besides, it worked great at first.

Not sure when the fuel filter & pump were changed but it's not a fuelling problem as there is plenty of fuel getting to the injectors, bleed off etc. The car is burning too much diesel right now due to the MAF being unplugged.

The reason I took the car into the garage in the first place was to have it generally checked over as it was new to me and I wanted someone with experience to give it a health check. They said the VCU and brakes were fine.

When I got the car back from them and I went to fit the new MAF I took off the air box cover and found that they had managed to get a vacuum hose trapped inside the airbox and the edges of the cover had cut through it where it entered and exited the box. I will replace this hose but I would find it very surprising it something like that could have this kind of effect so I'm still thinking it's some sort of sensor issue.

What do you think?

Change that hose. They can cause all sorts of problems.

The tuning boxes highlight any issues you already have.

I've just realised the problem pre-dates the hose being damaged.

I'll change it anyway just so I know it's OK.

Sounds like MAP sensor could be at fault. Do a search and you find all you need to know, doesnt take long to take inlet manifold off and clean. The reason disconnecting MAF will improve drive is because for mass air flow you need the input for all 3 sensors..flow, temp and pressure so with MAF disconnected ECU will disregard the temp and pressure ( MAP) inputs. Its a common problem in oily inlets...mine was choked solid last check. Hope this helps and you get sorted.