Vehicle Specific. > Fiddly Faults

Need advise

(1/1)

darkydave:
I have a niggle that I am hoping the more experienced Disco v8 owners can advise me with. Several months ago while towing my 23ft, 2 ½ ton boat I had an issue which I thought was something to do with my gearbox (auto). Now I believe it is something else.
I had it checked by the local Landover agent with the computer that came back with nothing.
What happens is the motor seems to stall off as you put your foot down at around 3000 rpm as if it isn’t getting enough fuel. What is strange is it will only do this after I have been driving for a while. When it happened the second time I came to the conclusion that it was a fuel filter issue. I then found out the fuel filter is combined with the pump. The agent is pushing a new fuel pump which I am happy to do if that is the problem. His comments were that the disco is running great and at first he couldn’t get it to play up.
I bought this disco for the sole purpose to tow my boat
 

discoveraus:
Hello Darkydave,

I dont have a V8 but I do have an D2 workshop manual which covers the V8 in some detail.

If the engine pulls along at steady conditions across the rev and load range the pump cannot be too bad or you would lose power at all speeds /revs as the fuel consumption increases especially with a 2.5 tonne boat on the back.

The symptoms you describe are similar to those of a faulty Mass Air Flow sensor.

Symptoms are ( according to the manual)

During driving, engine revs may dip before recovering
Difficult starting
Engine stalls after starting
Delayed throttle response ( this is your symptom)
Emission controls inoperative
Idle speed control inoperative
Reduced engine performance

A faulty Throttle position sensor will also cause your problem.

The ECM uses the outputs from these two sensors to "see" the change in throttle position when you call for acceleration, if either is slow to react (or missing altogether) you will get a lean mixture and a flat spot until the sensors send the correct signals to the ECM.

The manuals dont list any other causes of your symptoms that I could find.

I would check the MAF and TP sensors first before I laid out cash for a new fuel pump.

The manual shows the two mesh filters on the base of the pump but has no info on how to clean them if you do block them. I would try removing the pump and gently cleaning the filters at home before I bought a new pump because a pump will not be cheap. The labour to install it wont be cheap either.

Hope this helps.

regards

Discoveraus

tempestv8:

Yes, I'd agree with the post above that it may be MAF related.

The problem with the MAF is that if it degrades slowly over time, the engine's ECU will simply just recalibrate the fuel trims.  You can do a simple test - just start the engine and pay attention to the quality of the idle.

Then turn off the engine, disconnect the MAF and start it again.  If the MAF is in perfect working condition, you'll notice that the idle is rough but if you wait long enough, the ECU will probably compensate for the missing MAF and smoothen out somewhat, but the engine's responsiveness may be affected.

If however if you do not notice ANY difference in the engine's behaviour upon restart after the MAF was disconnected, chances are that your MAF is no longer effective.

I work on the personal rule that I replace the MAF sensor and the O2 sensors every 3 years or 60,000 kms, to ensure that the ECU is getting the correct data from these sensors.  The Land Rover MAF sensor is reasonably priced but the O2 sensors are very expensive, unfortunately.

Lawrance

Navigation

[0] Message Index