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Discussion Starter · #1 ·
When my 1.8t is cold it will at best get 10mpg ?! thats with absolute granny driving aswell, but once it is up to 90degrees it will nicely sit at the 30-40mpg range even with the odd bit of booting it about [:S]

Does anyone else expiernce this ?

Also when my car is cold it idles at around 1100-1200 for the first 1min or 2, do u think this is connected to the low MPG

i thought it was idleing higher because it was cold and the engine was puttin in extra fuel to warm it up quicker but i have heard this could be a temp or maf sensor but didnt really believe it but now i have also a flat spot between 3000-4000 rpm in every gear, is this just the standard poo mappin or is it prob?

As a faulty maf /temp senosr would explain the symptoms above, but like i say i dont no if its a problem or if its how the car is supposed to run, PLEASE help [:S][:S][:S][:S]
 

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When I turn mine on in the morning or indeed the evening after work mine idles at 1200 too for about 2-3mins and sounds like a tractor at the same time, or sounds as if you have lost the backbox!

After that it is fine, and yes, I get about 10-15mpg until it has warmed up too.

If anyone has a solution to this 1200 revs and the tractor noise I would love to know it, cus it sounds awful when your getting into your pride and joy in front of some nice lady.
 

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I thought all petrol engines run higher idle rpms when cold as the engine needs more fuel to start and run, similar to chokes in the old days. but agreed mine does exactly the same
 

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Discussion Starter · #4 ·
W36 EJO Do u have any flat spots ? My enigne is AUM, what code is yours ? wen i am bootin it against another car i nicely pull away untill the flat spot which last like 1/-2 secs then they catch up but end of flat spot im off again [:(] [:S]

Its weird [:'(]
 

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i don't have a petrol car but a similar thing happens in my diesel.

when cold i get about 25-30mpg, once up to 90C, i get 45-55mpg. the
reason for the increased fuel consumption at low temperatures is due to
two main issues:

1. Oil temp is low and therefore more viscous, also a lot of surfaces
have no oil on them as its still in the sump so you get increased
friction.

2. not as bigger a reason but the engine management system on most cars
sprays in a fuel rich mixture when its cold to prevent the engine from
stalling and also increase the flame temperature. this causes the
engine to heat up faster. once up to about 50C it leans the mixture out
until its stoichiometric (if you have a petrol)

hope thie helps
 

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Discussion Starter · #7 ·
Cheers dude [H]

Does anyone have a golf whos doesnt do it? As i dotn remember my car doin this when i first got it lol

What about the flat spot? what could be causing that ? Revo is calling out to me if this flat spot is normal? lol
 

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noticed this on my (ARZ)1.8t too.

When i start the car in a morning the car idles at about 1200rpm and my average mpg reading shoots down from about 29mpg to about 13mpg. It will carry on going down untill the rpms settle back to 700rpm.....

doesnt sound like a tractor though

after a few mins driving its back up close to 30mpg

its done it since i bought it in feb

Thought i may have a dirty maf ... buit i think its to do with the auto choke making the car drink like hell first thing in a morning
 

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Can't remember the code, but I'm on a Y reg 2001 model with DBW. I wouldn't mind so much if it wasn't for the noise.

The only thing thats nice about the noise is when it cuts out and you get that nice turbo/fan effect winding down, apart from that, its poo poo and can be quite hard to drive sometimes.

No I don't have any flat spots though, only a tiny bit of turbo lag say when I change from 3rd from high rev's into 4th quickly.
 

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sounds like a tractor? maybe it's misfiring? new ignition leads?

maybe moisture is causing misfire and when the temp of the engine rises the moisture goes as does the misfire..

I am totally guessing here.. not a mechanic.. lol
 

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I've realised out of experience to drive the car very easy until it is fully warmed up (sometimes the full journey) otherwise its like me on beer on a sat night!!

Mine also sounds like a diesel when starting, but has always done it. I also have the flat spot - most noticable in 3rd at around 4k revs or 5th at around the same 3.5k-4k revs, but i know the maf is knackered - i just keep cleaning it and its ok for a few weeks - will get round to changing it soon though. Oh yeah this is on an ARZ
 

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Discussion Starter · #12 ·
Maybe its turbo lag i am expeirncing, what is the optium rpm to shift at, as i think i shift to late, increaseing the turbo lag?[N]
 

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not sure if the tappets on the petrol engine are hyraulic but if they
are the lack of oil pressure will cause them to be noisy and may give
you the tractor type noise.
 

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Just had a look through the Bentley manual, the 1.8 engines do have hydraulic lifters.

This may aslo apply to cars with hydraulic lifters, but bike engines with buckets/shims or locknut/adjuster valve clearance adjustment should not be allowed to slow idle when cold.

It causes severe pitting and wear on the rear cam face (the face that allows the vavle to close).

GPz 600's were prone to this problem if they were allowed to cold idle bellow approx 3k.
 

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The sound it makes is as if it's meant to do it, but not all 1.8T's seem too.

If I had something to record the sound with I would go and do it, but I don't. If one of you others can record the sound please do, I will host it and then other people will know what we are on about!!
 

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i have a 1.8t. on cold i get around 18mpg upto 30, depending on how i drive.  I added a new dump valve.  it made quite a difference, dont know why.
 

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Discussion Starter · #18 ·
wharts a hydrolic filter ? [:S]

Deano did it make a difference for the worse or the good mate ?

I justgot 47.1 mpg droppin my girlfreind back how good is that !
 

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hydraulic lifter or tappets.

these things take up the slack in the valves so when the cam comes round to open the valve, it doesn't "bang" on the follower.
 
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