rangerovers.pub
The only place for a coil spring is up Zebedee's arse
Member
Joined:
Posts: 170

I have a very nice 2001 4.6 Rangie. It has never been very fast but drives very smoothly, quietly and sedately.

Having had various Rover engined TVRs with loads more power I am wondering if like TVRs is camshaft wear a problem with these engines? My experience is that 70–100 K miles is about the limit for a camshaft. Wear is hard to detect due to the hydraulic tappets so my question is: is this a common occurrence with the 4.0 –4.6 L engines?

Symptoms: when you plant your right foot, the car accelerates but seems very slightly hesitant and very slow for the revs to rise. On my private airfield, I clocked a maximum of 100 miles an hour and that took a while to achieve!

Car has done a genuine 80K

Of course it could be something else but I am at a loss as to what it could be.

Any ideas would be great!

Member
Joined:
Posts: 296

There is a lot to go through before you get the camshaft. Like MAF, O2 sensors, TPS to name a few. A good place to start is to reset the adaptive values.

In answer to your specific question, yes the camshafts wear in all Rover V8s. It is a known thing, however, the wear is directly related to servicing. If the engine has had regular oil changes every 5k and a new filter, good oil etc, camshafts should last 200 - 300k. Lack of servicing will drop this to less than 100k. You may also find you have a good cam, but a stretched timing chain, effectively retarding the cam timing. A fairly cheap and quick job to do. a Saturday afternoon's work.

Member
Joined:
Posts: 170

Thanks for the advice. I should start on the electrical side first I guess.
I am well versed in the Rover V8. I’ve built a 5.5 unit for my old TVR, 400 BHP.

How can I check the MAF, O2 sensors, TPS et cetera? Or is it just a case of replacement?

Member
Joined:
Posts: 296

The MAF, take it out and give it a good clean with MAF cleaner. You will really need a Nanocom to check the performance of the O2 sensors etc, but if they are off, life expired etc, then it can effect the fueling so performance.

Even little things like a dud ECU temp sensor can effect performance, as if the ECU thinks the engine is running hot, it retards the timing to restrict power output.

Member
Joined:
Posts: 170

I will speak to my son who is a mechanic. He has the usual mechanics laptops for diagnosing. I will take it from there. Thanks!

Member
Joined:
Posts: 306

My Nanocom is sitting idle if you want to use it Peter.

Member
Joined:
Posts: 170

That would be excellent as my son, (AA patrolman) couldn’t get any thing from the system with his gear.

I will give you a ring tomorrow if that’s okay. I still have your number.

Member
Joined:
Posts: 541

I wonder this about mine. Its really flat at low RPM's and only really wakes up above 3k or so. Given its a big torquey V8 that doesnt particularly like to rev it seems a bit "upside down".

I want to change the headgaskets soon as i suspect ones a bit leaky, perhaps thats a good time to check the cam, however is there any easy way to check for wear, or am i going to have to remove it and carefully measure everything?

Member
Joined:
Posts: 296

A quick look at it and you will soon see if it is worn. The lobes should be nice and sharp on the high end, not “curved”, and of course they should all look the same. It is quite usual to see three or four lobes worn and the rest OK, so the difference will be quite apparent.

Member
Joined:
Posts: 541

i suspect this job is going to snowball 😂

Member
Joined:
Posts: 313

If you remove inlet manifold valley gasket you can see camshaft rotate engine by hand you soon see if lifters go up and down the same amount ----- but issue could be MAF sensor not cam

Member
Joined:
Posts: 541

I've been thru a few MAF's, they're impossible to buy new, and copy ones are junk. I was tempted to try and datalog airflow against voltage, and figure out an adaptor to run a modern Bosch MAF on it.

I can easily acquire the voltage/airflow curves for a Bosch MAF, but the Sagem/GEMS MAF seems impossible to find, and ofcourse datalogging a broken one gives you useless data, so i've never bothered going any further. Someone who can tune the GEMS should be able to pull the airflow table out of the stock ECU, but i've never managed to find anyone willing to actually do it.

However the one i'm using now seems alright.

Member
avatar
Joined:
Posts: 6228

Engine fully warm, in neutral, all loads off:
@idle - 20 kg/hr +- 3 kg/hr
@2,500 rpm - 61 kg/hr +- 3 kg/hr

So if you assume it is going to be linear, you should be able to work it out. Or if it isn't going to be linear you should be able to work out the curve from a Bosch one. This does assume you have one that is working so you can read the airflow and measure the voltage.

Member
Joined:
Posts: 541

Its almost never linear unfortunately. They tend to design them with much more resolution at lower engine speeds. so the curve ends up exponential.

heres a few bosch curves for instance:

enter image description here

Member
Joined:
Posts: 541

Gilbertd wrote:

Or if it isn't going to be linear you should be able to work out the curve from a Bosch one. This does assume you have one that is working so you can read the airflow and measure the voltage.

Yeah, my plan was just to connect them both up to the engine in series and log the output from both. Since we know the Bosch curve, we can plot the curve for the SAGEM unit. But ofcourse, that only gives you useful data if both MAF's are actually working correctly.

Bosch Motronic ECU's have a 512x1 lookup table which contains voltage against airflow. Its pretty easy to extract it if you have a good definition file for the ECU. The SAGEM must surely be the same, but there doesnt seem to be many folk that have put the effort in to these ECU's.

Member
Joined:
Posts: 796

If you've got one that matches the figures in the test in the service manual it's probably safe to assume it's good. You can measure a bunch of GEMS ones and a bunch of Thor ones, and see if you can correlate any differences.

I wondered if it would be possible to fake it by measuring throttle angle and MAP.

Member
Joined:
Posts: 170

Thanks to David who has lent me his Nanacom.

I shall be having a go with it tomorrow………

Member
Joined:
Posts: 170

Had an initial fiddle. It certainly isn’t straightforward.

So far everything I can access seems to be normal including the air suspension which is brilliant. It was only spot on – 2 mm out from the target levels.

Various items seem to be locked, not sure where I go from there at the moment. Due to this I haven’t been able to access anything relevant on the engine although I did find that it seemed to be limited to 100 miles an hour. You have an option to change this to 120 which I did and when I was out on my personal airfield, it managed 108 mph!

Strange that the feeling when you accelerate flat out is that either it is an under powered engine fitted in a heavy body or that for some reason it is holding back. It accelerates very smoothly but not as urgent as I remember from a 4.6 I drove about 15 years ago!

Maybe I’m just used to the other couple of cars in my stable and my old 5.5 RV8 TVR, Maybe.

any pointers?

Member
Joined:
Posts: 313

Simple solution take engine out of the and put it in range rover ---- I've got a Buick 300 V8 in a rover p6 I'd have swapped out but I couldn't handle 7mpg 🙄

Member
Joined:
Posts: 313

Have you checked the butterfly valve in throttle body is actually fully open when gas pedal is right down---- cables do stretch