General 100hp mpg drop?

[DaveMcT]

MES will probably not see a coil problem. You would have to work it out from other symptoms.

There are many parameters that affect fuel consumption - air filter - air flow measurement - engine temperature and anything onwards from there. All you can do is get the readings and look for discrepancies.

I don't know if the MES free version will give what you need. Try posting in the relevant forum section.

 

[dac69er]

MES free let's you monitor everything, but only a few items at the same time and only for 30 min sessions.

I measured resistance of all coils when the engine was hot and all read 0.8 ohms.

There just doesn't seem to be any issues that I can see, it's a strange one!!!!?

 

[dac69er]

Any other suggestions regarding This?

My 200bhp modified starlet turbo gets better mpg than the panda!!! Something must be wrong!?!?

It starts and drives perfectly fine. Performance is as expected. No smoke from the exhaust and no ecu fault codes or anything obvious on MES.

I am really at a loss as to what has changed on the car to cause the reduction in mpg!?

 

[DaveMcT]

Mine went on to three cylinders on my Friday night drive home. On Saturday, I started it for a few seconds - still really rough. One exhaust outlet was cold so most likely a spark. I replaced the plugs but it turned out to be the stick coil. New coil and the car feels like its been reborn so despite no warning lights I suspect that coil has been failing for some time. It's too early to say how it affected fuel consumption but can't have helped.

The coil connecting cable rail was brittle. On every connector, the yellow locking tags crumbled away and the plastic harness cracked. I patched it up with cable ties so its not going to fall off but will probably get a new connecting harness.

I have not worked out how the large connecting block adjacent to the cylinder head actually disconnects but it does not look like a simple pull out jobbie.

 

[dac69er]

i am kinda suspecting a coil/coils. my only issue is that it drives really well, its simply the fuel consumption that seems off!

it is quite pricey to replace all 4 coils on a whim which is why i am a little reluctant to do it!

i know what you mean about the harness, it turns to dust once the mileage is up and the heat has got to it

from memory, i think the connectors are pretty straight forward to remove once you know the "knack" i would have to have a look and refresh my memory on that though!

did you get an engine warning light when one of the coils went? what mileage is your car currently?

it will be interesting to see what your fuel consumption is like now the coil is replaced. you did mention that yours was pretty crappy too

 

[chris3234]

i am kinda suspecting a coil/coils. my only issue is that it drives really well, its simply the fuel consumption that seems off!

it is quite pricey to replace all 4 coils on a whim which is why i am a little reluctant to do it!

i know what you mean about the harness, it turns to dust once the mileage is up and the heat has got to it

from memory, i think the connectors are pretty straight forward to remove once you know the "knack" i would have to have a look and refresh my memory on that though!

did you get an engine warning light when one of the coils went? what mileage is your car currently?

it will be interesting to see what your fuel consumption is like now the coil is replaced. you did mention that yours was pretty crappy too

You could try one replacement and try it each cyclider/plug for a week see time see if it improves the mpg any?

 

[dac69er]

That's assuming it's only 1 coil at fault of course.

I guess I could try that. I'm still not sure how cost effective that is. Even the cheapest coils on eBay at around £20+ the relatively small reduction in mpg would take a while for me to recoup the expense if it does improve it.

 

[DaveMcT]

The performance and mpg have improved on mine with it's new stick coil. But doing mostly motorways and duals, it's unlikely to get above 40mpg.


It cost £43 from my friendly local parts shop so I'm hoping its the only one. On Shop4Parts they cost £45 plus VAT and delivery so very not cheap.

A basic test of failing coils means swapping them about and see if the cool exhaust stub "moves".

 

[dac69er]

The performance and mpg have improved on mine with it's new stick coil. But doing mostly motorways and duals, it's unlikely to get above 40mpg.


It cost £43 from my friendly local parts shop so I'm hoping its the only one. On Shop4Parts they cost £45 plus VAT and delivery so very not cheap.

A basic test of failing coils means swapping them about and see if the cool exhaust stub "moves".

i have found some substatially cheaper coils from some dubious sources, but these may be trash anyway!
im tempted to give them a try though :slayer:


i cant see a coil that is only weak and not actually causing a misfire creating a noticeable decrease in the temp of one exhaust outlet port on the manifold without use of temperature probes in the runners.

 

[DaveMcT]

i have found some substatially cheaper coils from some dubious sources, but these may be trash anyway!
im tempted to give them a try though :slayer:


i cant see a coil that is only weak and not actually causing a misfire creating a noticeable decrease in the temp of one exhaust outlet port on the manifold without use of temperature probes in the runners.

If you fully warm the engine the only way to get any information from the exhaust temperature would be via an IR thermometer. I used that method to set the throttle bodies on my bike.

My quick and dirty coil test runs the cold engine for less than 10 seconds. Enough to warm the exhaust runners. Any that feel cool are suspect. Swapping the coils around is long enough for the metal to cool back to ambient for a retest.

A cold engine tends to show weak coils more than a warm engine.

 

[dac69er]

well i managed to find some coils for £6.99 each

i have bought a full set so lets see how they go when they turn up.........

 

[DaveMcT]

well i managed to find some coils for £6.99 each

i have bought a full set so lets see how they go when they turn up.........

Wow! :worship:

That's little more than I paid for just one coil.

 

[dac69er]

Wow! :worship:

That's little more than I paid for just one coil.

May be false economy, but worth a try for fault finding sake.

I will take one for the team and share details if they are any good. They look good quality in the pictures!

 

[dac69er]

Well they work. Maybe a bit more pull at low rpm, but that may just be in my head.

They seem decent enough. Just need to test them long term.

Originals on the left, new ones on the right:

 

[DaveMcT]

I have one coil with damage to the flange where the cable connector clips on. But the coil which actually failed looks just fine.

 

[dac69er]

UPDATE:

Went on a good run today and got an average of 48mpg. Back to how she was. Midrange is also noticeably better too.
If I tried I could manage 50mpg without too much effort.

Definitely worth the sub £30 for the set.

These are what I bought: ebay item number 283538158008

 

[JustApanda]

Bit of a thread revival. Would a failing coil/s or spark plug/s cause a slight hover in the revs when lifting off the accelerator when changing gears... I’m sitting with a combined average consumption of 7.1l/100km (38mpg if the conversion is to be believed) I’ve also noticed that when coasting in gear the consumption never drops below 2l/100km . When i did this with my Up! It would always be zero... would the coils be the cause or dirty throttle body?

 

[A3jeroen]

With the engine running, consumption can never be zero...

For the hovering, my money would be on the throttlebody.

gr J

 

[DaveMcT]

The computer never shows better than 99mpg (whatever that is in L/100km). It's wrong because coasting on a closed throttle uses zero fuel. However, my displayed average consumption figure is pretty close to brimming the tank and measuring against distance traveled.

The uneven revs could be many things from throttle body to accelerator pedal - it is drive by wire. I would say it is unlikely to be ignition coils but you never know. If you get a copy of www.multiecuscan.net you'll be able to datalog the engine parameters which should allow a diagnosis.

 

[JustApanda]

With the engine running, consumption can never be zero...

For the hovering, my money would be on the throttlebody.

gr J

Coasting in gear? It does use fuel yes, but it shouldn’t be that much should it? How much fuel is fed to keep the engine idling?

So a throttle body clean is in order? Ill
Search for a how to on the forum. Very new to fiat and their layouts but can do most of the work myself luckily...