P38A Mileage Query

Oddly I like resetting mpg meter. It does seem to be slightly random at times.

Mileage dropped before I changed plugs and didnt improve afterwards
I have got another week of shortish journeys then back to longer ones and will see what happens
Will check O2 sensors on nanocom too

How do I check MAF?

Does having an old fuel filter affect mileage?

oakey said:

Does having an old fuel filter affect mileage?

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Might restrict the amount of fuel getting through and push it up. It'd have to get pretty manky for that though.

I don't have the figures but it's a voltage reading taken at 1000 and 3000 rpm. Only problem with fuel filters is the car won't start if its very blocked!
The Lucas injectors at that mileage are usually dicey. I think the actual reading is arrived at by the injector pulsing( knowing fuel pressure and injector delivery amount) over the distance derived from the abs sensors( new wheels and tires?)

No not new tryes etc
Fuel filter has done at least 120k cos I didnt know I had one
Not used injector cleaner stuff in petrol for ages

The lucas injectors can let by usually resulting in high revs on starting. The correct Bosch injectors are a big improvement and a straight swap.

I will have a look and see which ones I have ta

johnnyb70 said:

The lucas injectors can let by usually resulting in high revs on starting. The correct Bosch injectors are a big improvement and a straight swap.

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What do you mean by "let by", Johnny?

If you have changed components reset the adaptive values to wipe the ECU memory or the ECU will be running the engine as it did with the worn components fitted.

By let by I mean the injector pulse no longer delivers a crisp waveform. They open slightly before and close slightly after. They also have a very poor spray when they get older. Even at 100000 miles there not great. There not available either. I attribute the Thor's better fuel consumption mostly to using Bosch gen 3 injectors. PS only gen 2 injectors will work with gems(see mark adams site for new and recon) I got mine off an American mustang breakers.

If you've just changed the plugs don't reset adaptive values. If you've changed a cam maybe. But gems will learn to run ok after one drive cycle. If you've changed the throttle sensor iacv yes to reset the idle.

Just changed plugs n leads
Mileage plummeted before anything was changed

Check the fuel trim. See what adjustments are being made from base.

When I got mine (4.6 Thor) in April, the readout stayed around 11-12 mpg. One good long motorway blast and now the 'local' running about reading is 15-16 mpg. It must have adapted in some way (or there were some cobwebs in there). The mpg readout is not 100% accurate: compared with brim-to-brim readings over several hundred miles:

Local: brim-to-brim 16, readout 17.4
Motorway: brim-to-brim 20, readout 22.

Hope to plug it in to Nanocom by weekend and have a looksee at figures.
Yes dashboard may be out a bit but just been using as comparison.
Will get a long run next week and see what happens

oakey said:

V8 4.6 auto 1995 178k
Purely based on the dashboard figures, I used to get approx 20 - 21 mpg
For the past few weeks I get approx 25 - 16 mpg.
Anyone any ideas?
I just changed all plugs and leads and they certainly needed it.
All the plugs looked the right colour so I guess the mixture is ok
I have a nanocom, what should I look for?

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My P38 is giving me 11mpg towing a 3.5ton horse trailer,

It is stuck in sports mode making it difficult to lockup in top.

I have had 20mpg solo when auto box was not playing up.

So check the box is in manual mode.

I will check ta

Gearbox seems to e working fine