Occasional loss of power.

[Delta66]

Originally Posted by Stephen Edwin

Delta. I can't advise. I am wondering in case it helps any advisers. Is it a loss of power as in total loss of power, or a significant reduction of power, a refusal to accelerate, a slowing down of the vehicle perhaps?

Reading between the lines I'm guessing a reduction of power.

Dave. You mentioned the possibility of an over heated fuel pump fuse. Do the 700/900 cars have fuse boards designed for ceramic bodied fuses as per the 240?

A reduction in power would be a better description, like a limp home mode has been selected when a modern engine has detected a problem. The car does not suddenly have no power at all.

[Laird Scooby]

Originally Posted by Delta66

Since Dry Fuel is basically meths, the problem started after I added the Dry Fuel and the consensus is that there will be no more of that additive left, I think I can rule out it as the cause and would be reluctant to add more.

The revs do drop as the power drops, the car will not rev and even foot to the floor with the accelerator produces nothing, the car keeps slowing. I am now careful about foot to the floor, as the power returns all of a sudden and the car will shoot off.

I replaced the HT leads a while back when trying to sort uneven idling.

Since you added the "Dry Fuel" in an effort to cure this problem from your original thread you posted about the same problem, i'm not surprised the fault is still there considering the small amount contained in the Dry Fuel bottle.
Experience, trial & error has proved time after time, not just for me but others as well that the optimum concentration is 10% meths in fuel. Therefore 2L in a maximum of 4 gallons of petrol (18L) is in fact spot on - the Dry Fuel bottle is 325ml - less than 1/6 the amount proven to be effective.

That's assuming it's fuel related.

The next question i asked was if the rev counter dropped to zero. You replied the revs drop. That doesn't answer the question.

The revs dropping is a given in a power loss situation, the power is removed, therefore the engine is trying to die and the engine speed/revs drop accordingly.

Does the rev counter itself drop to zero? This is an important diagnostic question and needs answering correctly.

It's impossible to try and help if you aren't answering the questions correctly - first i don't know if you've understood the question, second i don't know how to interpret your answer. Please see above for the explanation of that.

If you don't understand the question, i'm happy to rephrase it or explain it further so we can get to the bottom of this for you.

Originally Posted by Stephen Edwin

Delta. I can't advise. I am wondering in case it helps any advisers. Is it a loss of power as in total loss of power, or a significant reduction of power, a refusal to accelerate, a slowing down of the vehicle perhaps?

Reading between the lines I'm guessing a reduction of power.

Dave. You mentioned the possibility of an over heated fuel pump fuse. Do the 700/900 cars have fuse boards designed for ceramic bodied fuses as per the 240?

Thanks Stephen - your response has highlighted exactly what i am trying to explain above.

As for the fuses, thankfully the 7/9xx series don't have the horrendous "Continental" ceramic bodied fuses. They have the later, more reliable blade fuses. However, i know from personal experience, the fuel pump fuses in 740s have a tendency to get hot because of poor connections. This can cause the fuel pump to cut-out until the fuse holder cools down. Have a look here :

https://www.vlvworld.com/indexframe....al/700_0_3.htm

On my first 740, fuse #1 had been moved to position 23 (spare) and still overheated causing burning/discolouration to the plastic around the fuse. It also meant the car would completely cut out and not restart for about 10 minutes when driven for more than half an hour. In the end, i fitted a new, separate fuseholder and problem solved.
My second 740 had already had a new fuseholder fitted, just for that circuit. My last 740 was strangely absolutely fine, despite being the highest mileage out of the three.

As the same fusebox was used on the 940 it's entirely possible the fault still exists as it seems common.

[Delta66]

Originally Posted by Laird Scooby

....
It's impossible to try and help if you aren't answering the questions correctly -
.....

OK, just leave it for now thanks.

[Stephen Edwin]

Delta.

I really hope you will continue this thread, please. It is very important in my opinion indeed it involves safety. Absolutely important for you, and also for anyone else who might encounter the same symptoms.

[Dirty Rooster]

Originally Posted by Delta66

OK, just leave it for now thanks.

No.

Next time you feel the loss of power, look at your rev counter.
If it has dropped to zero but the engine is still running that indicates a certain thing failing,
if the rev counter is normal during your power loss tell us.
We can rule things out one by one this way.

[Delta66]

Originally Posted by Dirty Rooster

No.

Next time you feel the loss of power, look at your rev counter.
If it has dropped to zero but the engine is still running that indicates a certain thing failing,
if the rev counter is normal during your power loss tell us.
We can rule things out one by one this way.

I am pretty sure it did not drop to zero. I was on a busy 50mph road with an artic behind me, so I was concentrating more on keeping safe as I was slowing down to 10mph.

But other times it has done it, it has definitely not dropped to zero.

It has been running fine since I originally posted.

[Laird Scooby]

Originally Posted by Delta66

I am pretty sure it did not drop to zero. I was on a busy 50mph road with an artic behind me, so I was concentrating more on keeping safe as I was slowing down to 10mph.

But other times it has done it, it has definitely not dropped to zero.

It has been running fine since I originally posted.

That more or less rules out the CPS and indeed most of the ignition system, with the exception of the coil and/or king lead.

However it it has been running fine since, what else have you done differently recently? Have you changed filling stations? Has the last of the condensation finally gone from the tank? Have you been using the car more frequently?

[Stephen Edwin]

Does this car have an air mass meter? They can go faulty in more than one way, including intermittently going in to a sort of limp home mode.

Does the car have a built in LH type code reader? Does that show any code[s]?

Intermittent faults are a pain to find. And your experience with the HGV must have been horrible. Good luck getting this sorted.

[Delta66]

When I had problems with the lumpy idling and it actually cutting out, I replaced the MAS and ignition leads. I did a idle valve control clean and added a fuel system cleaner and between that lot got the idle fine and cutting out stopped.

I then had an ABS problem and got a reader to identify which one was faulty and it did not kick up any other codes, other than the MAS, which I presume was an old fault and once cleared was fine.

There has been no change in the use of the car, it gets run most days and I use various local garages (BP, Shell, Esso and Jet).

Of course, it has been fine since I originally posted.

[Laird Scooby]

Originally Posted by Delta66

When I had problems with the lumpy idling and it actually cutting out, I replaced the MAS and ignition leads. I did a idle valve control clean and added a fuel system cleaner and between that lot got the idle fine and cutting out stopped.

I then had an ABS problem and got a reader to identify which one was faulty and it did not kick up any other codes, other than the MAS, which I presume was an old fault and once cleared was fine.

There has been no change in the use of the car, it gets run most days and I use various local garages (BP, Shell, Esso and Jet).

Of course, it has been fine since I originally posted.

If it's any consolation, it took me 9 years to find an intermittent battery drain on one of mine. I'd avoid the Esso and Jet petrols for a while and just see if it behaves itself, none of my cars have ever run right on those.