Thought is was time to start a new thread as my noisy injectors thread was getting rather long and apart from the noise, what I am actually trying to achieve is the seemingly fanciful mpg that many others here seem to get. I also want to get rid of the lumpy start up. :yes:

I've had the engine checked and was told it was running fine and sounded OK by two different mechanics, even though to me it sounds like a bag of spanners.

No codes show up on diagnostics.

New stat.

Full coolant flush and refill with GL12.

I have adjusted the valve clearances as specified.

I have run some injector cleaner through the fuel system.

Plugs are fine.

Air filter is new.

Throttle body is clean, as far as I can see.

New exhaust throughout including cat.

The car only does a straight 10 mile run to work and 10miles back and I mean straight, only one junction and I rarely need to stop at it. Pretty much constant 40mph all the way, as it's 5.30am and no hills really.

The mpg was at about 25mpg a few weeks back, but is now about 30mpg. I suspect this is more to do with the warmer ambient temperature than anything else.

Thanks to all those that have contributed so far, but any more suggestions chaps?

Edited 28 March, 201016 yr by myjalopy

Hmmmm, tricky.

I taught my son to keep in the green zone on the rev counter and to use engine braking as much as possible when slowing down; ie change down a gear rather than brake all the time.

Other than that, all I can suggest is giving it another week or two and keep an eye on it.

You've checked for binding brakes, wheel bearings, under inflated tyres, etc??

Hi, yes checked the brakes, bearings and tyres are at 30psi, possibly slightly higher than required. Even had a look for fuel leaks. I am not lead footed and as you suggest, keep within the 2-4k rpm.

It really is getting me down as it was bought as a cheap runaround for work. So far it is anything but and has cost me more in bits and time than my 11 year old Scenic has. It looks immaculate, in and out and has only 45k on it, meticulously serviced by the previous 2 owners from new new, so I am puzzled why I don't get the mpg others do

Your tires must be pretty new, I think mine are old, and at 30 they look really deflated, so I've pumped them up to 40. Haven't really noticed much difference in MPG though.

Yep, new when I bought the car a few weeks back.

40psi seems way too high, regardless of age. It doesn't matter what they look like, the psi should be correct. The ride will be hard as well as putting extra strain on the suspension components and the tyres themselves.

I think mpg will only be affected by really low pressures, because the rolling resistance increases.

Edited 28 March, 201016 yr by myjalopy

have you done a compression test on it? i'm think along the lines of a leaky or burnt out valve or worn piston rings

my felicia pickup is over 100bhp and i can still get 44ish mpg out of it so there is something funny going on with yours

in regards to diagnostics, sadly they often don't tell you an aweful lot unless one of the sensors is out of it's normal operating range, it's still possible for a sensor to be faulty and still be sending the ecu that is still within it's normal range of operation....

does the exhaust gas smell all fuelly when it's idling?

have you checked the condition of the fuel pressure regulator vacuum hose?

have you done a compression test on it? i'm think along the lines of a leaky or burnt out valve or worn piston rings

does the exhaust gas smell all fuelly when it's idling?

have you checked the condition of the fuel pressure regulator vacuum hose?

No, I haven't done a compression test, but that would be a good idea, thanks. The engine seems to pull ok, so I never thought of doing one. Do you know what readings i should get?

The exhaust doesn't smell of petrol, just the usual fumes.

No, I havent checked the regulator hose. Thanks again. I imagine if there are any cracks or damage it would be a bad thing, but what does this hose do and how would it affect fuel economy?

the fuel pressure regulator is referenced to manifold vacuum levels, this raises and lowers the fuel pressure in line with manifold air pressure/vacuum. without the vaccum line on there the fuel pressure will be slightly higher so you would use more fuel,

Valve clearances?

This is the MPI not the SPI.

How many miles are you getting per tankful?

the fuel pressure regulator is referenced to manifold vacuum levels, this raises and lowers the fuel pressure in line with manifold air pressure/vacuum. without the vaccum line on there the fuel pressure will be slightly higher so you would use more fuel,

I see, thanks. It looks fine, but the manifold end was welded on. Started the engine, took the pipe off the regulator end and the revs went up a bit. Put my finger over the end and got suction and revs dipped, so I think it's all OK.

Edited 29 March, 201016 yr by myjalopy

Valve clearances?

This is the MPI not the SPI.

How many miles are you getting per tankful?

Valve clearances should be fine as they were set to specified tolerences last week. They were slightly too tight before that I reckon as the feeler would barely go between them at all.

Yes it's the MPI.

I have never run a whole tank down as that means I would have to fill it up again, I filled up and just did say 100 miles, then filled up then 100 more and so on. Miles divded by fuel used gives me mpg. Do this 3 times to get an average.

Edited 29 March, 201016 yr by myjalopy

Hmmm. Definately doesn't seem great MPG.

On a run like that I would be looking at getting at least 40mpg in Nelly. On a good 'spirited' run she would never go below 27mpg which is the lowest I have ever got and that was a very long run thrashing it quite a lot.

Almost seems like something is causing too much fuel to be injected/used.

I would definately do the things Tom has suggested and would have thought the answer will lie there somewhere.

Phil

40mpg from ours skodas isn't looking so good now that these guys from america have come along:

http://electric-vehicles-cars-bikes.blogspot.com/2010/03/4548-mpg-achieved-at-2010-shell-eco.html?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+blogspot%2FpEcq+%28Electric+Vehicles%29

2487.5 mpg.....now theres a dream

I would definately do the things Tom has suggested and would have thought the answer will lie there somewhere.

Phil

Yes, just need to sort a compression test when I get the time and someone to do it.

I see, thanks. It looks fine, but the manifold end was welded on. Started the engine, took the pipe off the regulator end and the revs went up a bit. Put my finger over the end and got suction and revs dipped, so I think it's all OK.

ok, that sounds normal to me... taking the hose off will allow a small amount of air through which will increase the idle speed, replacing the hose back on it dropped back so you can assume there is no vacuum leak there

doesnt sound good, mines got FSH etc and even when i do a full tank round town doing no more than 5 mile trips i still get 35mpg, in the last week, i've been commuting 100 miles each way (5 times each way so 1000 miles in 5 days!) and its doing about 43mpg so not as high as i'd like but still a decent figure!

sorry cant make any suggestions as to how to achieve these figures, i'm quite heavy footed as well, and mine has the rough starts, runs badly for the first 5 miles or so! i only live 1 mile from the dual carriageway so its 5th gear driving almost anywhere though!

Maybe I should try the lead footed approach.