Pitbull69

I was half expecting my car to fail, as the exhaust is always black and sooty looking, will be black within a day of me cleaning it. but it passed today with no advisories.

I was hoping it would fail, and prove that there was something wrong with the car as no matter how I drive it I only get 20-22 MPG. I know the ST170 is famous for bad MPG but surely not this bad. I have seen some people say thye get 320-350 miles from a tank, but I couldn't get near that.


My mate said if it passed the MOT it must be fuelling correctly, which I guess makes sense, but the MPG doesn't.

looking at the readout it didn't just scrape by the test either, seems at the lower scale, Although I did put a bottle of redex in the tank before filling up not sure how much that would influence the emissions test

So should I just accept the low MPG figures, or would anybody recommend anything I can change, I have already changed the HT leads to Magnacor ones, ordered some new spark plugs, but not sure where to look next.

Fullflush

Id start changing sensors, 1 every time you fill up (if possible)

ben_frst

by a cheap obd2 reader with live date and go play

Pitbull69

What one would you start with, I'm thinking coolant temp sensor,

So something like this ?

http://www.ebay.co.uk/itm/2613659821...112%26_rdc%3D1

xr_craig

iTrader: (2)

Sounds like a great plan.

I'd speak to someone who knows st170's and see if they have any ideas before I started throwing money at it.

Fullflush

Yeah the coolant temp seems my most likely bet

Fullflush

Well there aren't many sensors, elimination is a good method

stevieturbo

Or try a mechanic ?

BIG WULL

iTrader: (5)

please tell me you are having a laugh?

GVK.

MOT emission test is only done at very light throttle to reach ~2500-3000rpm ish

ECU will try and keep the AFR at 14.7:1 (Lambda 1) during the test as it does at idle and light throttle cruise situations.

..Unless you drive like a nun, you're not replicating this with 'normal' driving.

stevieturbo

That would depend on your definition of normal.

Most petrol engines run at closed loop stioch under all "normal" driving conditions.

Now if your putting the foot down and boosting everywhere...that's a different matter entirely, and of course you'd expect it to use more fuel.

GVK.

Oh yes, depends of course on if you're driving with economy in mind (Like a nun)..or otherwise!

Full throttle accel will not be in closed loop..

RichieST

iTrader: (2)

I used to get around 280 to a tank from my old ST170.

vaughant

iTrader: (1)

When these were new the carpark in my old work (ford plant) was full of them, mostly in grey and 3dr with the 6spd box. I'd go so far as to say within a year there were about 4 left as everyone had enough of the horrendous economy, all low to mid twenties at best.
Great engine and overall package but yes they are very thirsty for what they are.
On an aside, my old focus estate 1.8 petrol never did better than 30 mpg which is a shame as it was an amazingly nice car to drive.

Pitbull69

Thanks guys some interesting comments.

I have some new plugs that should be here soon and I purchased that diagnostic scanner, so I will have a look and see if that shows anything.

RichieST

iTrader: (2)

For ignition components don't use anything other than genuine ford/motorcraft. I've seen plenty of faults caused by branded plugs and leads etc. For some reason zetecs just don't like them.

mondeoman81

Change the lambda sensors even thou they dont register as failing

ben_frst

Yep that will do you just need to read how to decipher its findings I would say ecu temp sensor a vacuum leak or lambda/maf fault does it idle high? or hunt at all?

Pitbull69

The guy I bought the car off said he did a full service before I bought the car, so im hoping maybe he used different plugs, I purchased genuine ford ones. will check them against each other once they arrive.

I have got paper work saying they was changed about 6 months ago, I know some cars are fussy with sensors, would you know if its the same with this,

Brilliant, I have used diagnostics before but the only live data was that free app on my phone to check my boost gauge was working on my vRS. so hopefully I can work it out eventually. I would say it does hunt but not really bad, but sometimes especially when in reverse it has stalled a few times. and can be very lumpy when cruising along,. its fine if I have my foot planted though

BM08

Thats the first time in my life ive ever heard someone say ''Well actually i was hoping it would fail''

bamba

it may be worth checking the fuel filter.If the fuel coming out has a slight brown tinge to it(hopefully the filter hasn't been replaced recently) I would be looking at the fuel pump.
the pump has two filters on it.Mine were really badly blocked-so much so infact that I couldn't believe it was running still. There were no fault codes produced,the only symptom was a flat spot when revved hard higher in the rev range.
The filter were that bad I replaced the complete pump assembly rather than clean the filters.
other faults include inlet manifold runners/control and lambda sensors-but usually give a fault code.Other thoughts could be partially blocked cat/exhaust for poor economy. ok at emission test range but not general driving.I thought my st170 was good on fuel-did have a Bluefin though.

Hope this helps Glyn

bigjohn0

Drop me a pm if you get no where with your car mate as i am just down the road from you and have diag stuff to tell you whats going on with it.

kosman

my mate dumped his in his garage about 2months ago because he was fed up of fueling it up.

Pitbull69

Haha admittedly that sounds bad, and I'm very glad it passed (Honest) was more to get an answer to above problem

Cheers mate, sort of, I am waiting for eurocarparts to issue me a refund so I can order a fuel filter as there was no paperwork for having that changed any time recently, Hopefully not the fuel pump as I have read they can be costly, I have a receipt for a brand new inlet runner from ford think it cost something like £270 so hopefully that's ok too. exhauts is brand new from cat back, so still leaves cat as a possibility, just glad to hear someone else say there MPG was ok in a ST170

Cheers mate, much appreciated, my diagnostic should be here tomorrow, but if I cant get anywhere with it I would love to take you up on your kind offer.

Pitbull69

Well I changed the spark plugs today, they wasnt too bad but I didnt like all the crap over the thread of them, not sure what caused it either.

But they deffo wasn't standard ford plugs, Bosch Super +

Haven't made much of an improvement, but would the ECU need to get used to new plugs or would that be an instant change ?

I also got my diagnostic reader today, says there was no codes stored, so thats a good thing, checked the live data but wasnt sure what I was looking at, and only checked it whilst parked and revving it,

Would anyone know what I should be looking at, as I cant look at it whilst driving so gonna have to ask the wife to monitor it while I drive,

Here is a few pics I took of the live feed today