Petrol Smell & Missfiring

[Jonnyf007]

Hi all,
Could someonr please give me some advice where to start, recently I've had a strong petrol smell from cold and goes away when the car warm up . Also the car has a really bad missfire on around 1000rpm. Is this likely to be a coil pack and a labda sencor to cause these issues? I have checked the exhaust for any leaks but is perfect and I have no warning lights on my dash. But this problem does not show up as a fault on a diagnostics unit.
Please could you give me some. Advice.
Many thanks
Jon.

 

[daveypower]

I'd through a Coolant temp sensor in the mix to??

 

[TheEvilGiraffe]

Standard exhaust ? Is the cat there still ?

 

[MartinR]

I'd through a Coolant temp sensor in the mix to??

Coolant temp sensor won't cause a missfire but can cause it to run on the cold map hence why it stinks of fuel.
Personally i would look at the coilpack,plugs and leads.

 

[Renatoccg]

I'm with the same issue ish on my mk2 K4M 2006 sirius 32 flex.
I have a k&N inbox fitted, and removed the cat, but only one lambda though.
first it loss a bit of power, then was misfiring when cold, then all the time if WOT under 3000rpm.
scanned the ecu, nothing wrong.
changed spark plugs, nothing happened, but the plugs was full of carbonization(waaay rich).
Changed the coils, stopped the misfiring for a few days. But it is still lacking power, and starting to misfire when wot at low revs.

While scanning the ecu, the lambda graph seems normal, oscillating around 100 and 900mv.
Guess the last "cheap" thing that could be is the cts, before testing the electronic tb or the ecu itself.
But if there's the cts to blame, why it doesn't have a fault code shown, and why it shows the temperature normally on the dash reader?

Cheers!

P.S.:
The cts can cause the misfire, indirectly. When running on rich mix for some time, it creates a carbon deposit on the spark plugs, due to the fuel excess and the low temp of the combustion chamber. Mine was like this.

 

[flat-eric]

Well going on what happened with mine mate, first thing to check is the plugs as its easy to give a visual check. my duff plug was very obvious! if its not plugs or leads, then get it into a decent (Recommended) garage for a check up. Dont waste time replacing stuff as it can easily turn into a very costly fault finding method!

 

[Jonnyf007]

Thanks all for your replies,
i have a aftermarket exhaust with the cat and its perfectly fine no leaks etc.....
will try looking at the plugs , coil pack etc first with a visual check
I would not of thought a cooling temp sensor would be my issue or would it my car doesn't overheat etc...
Cheers
jon

 

[Jonnyf007]

Thanks all for your replies,
i have a aftermarket exhaust with the cat and its perfectly fine no leaks etc.....
will try looking at the plugs , coil pack etc first with a visual check
I would not of thought a cooling temp sensor would be my issue or would it my car doesn't overheat etc...
Cheers
jon

 

[daveypower]

coolant temp sensor wont cause the car to overheat, your thinking of your thermostat, it adjusts the air fuel mixture with the heat of the engine coolant, it helpss on start up etc, and can cause a misfire/ rough running.

 

[Renatoccg]

The fact that the cts has 3 wires on it. Can the signal sent to the ecu be different from the one sent to the dash?

 

[Jonnyf007]

Ok, today I changed the cts sensor, and my coil pack, my misfiring problem seems to have gone so I take it the coil pack had solved that problem, but still I have a really strong petrol smell and I have noticed that I have some black stuff inside my tailpipe :/????
my car hasn't lost any oil etc nor can I see any leaks, car heats up ok and I haven't lost any coolant, I do get the occasion of white smoke from startup but then goes! Does anyone have any ideas on this?????
CHeers
jon

 

[Renatoccg]

Jonny, the black stuff is because when misfire happens, partially burned fuel is thrown on the exhaust. Would be nice if you could test if while in wot, there is dark smoke coming out of the exhaust. Probably it's only possible to note thar from outside.

When I changed the coil pak, the misfiring stopped too, but it's back again in some occasions.
Just tried fault reading again, no fails again. The cts is working fine, reading up to around 102C when the fan starts.
Though one thing caught my attention, the O2 sensor wasn't reading above ~650mv.
Usually it varies fastly between ~50mv to 950mv. Tried other 2 cars on the shop, and they were ok. Now, is my O2 sensor needing replacement, or is something else causing the afr to be that way?

 

[Jonnyf007]

so i finally got to the bottom of my issues today, I had taken the car out for a quick 5 min drive and noticed it took almost 5 min for my temp needle to move from the bottom..... After never getting any problems with my temp needle going to mid way showing the car was heating up correctly it dawened on me to thing could it be something as simple as my thermostat..... so i went and got a thermostat today and coolant and changed it...... let the car warm up needle back to where it has always been...... so i left the car cool down for a few hours then went back to check and warm it up then presto the fuel smell had gone and the missfirng had completely vanished once it had fully warmed up..... Even tho my temp needle was always sitting as it should be i had actually had a dodgy thermostat that must of been causing my car to run cold causing the common missfire and the overfueling smell.
Ive been out in it all afternoon shocked that all is back to normall just by changing the thermostat!!! UNBELIEVABLE

 

[Renatoccg]

Nice thinking!
I'll try to check it too.