318i very strange missfire

[E30-318is-auto]

ok so as you can guess my 318i is missfiring , but here is the strange thing its overfuelling and blacking the plugs so i clean them and it settles again but today i went and bought 4 new plugs and it has started missfiring worse than ever, does anyone have any idea why it would be worse with new plugs?

[zaust]

no gap's set.

or

wrong plugs

or

faild lead

[Chris36]

As said check the gaps, may need a cooler plug. What make plugs? Hopefully NGK and not Bosch. Any mods?? or air leaks?

[Brianmoooore]

If the previous plugs were black, then find out why! It's misfiring because it's over fueling.

[E30-318is-auto]

so what could cause over fuelling, i have already replaced ecu but other than than i have no clue what could be causing it.

[E30-318is-auto]

ths is really baffling me now put new plugs in sunday missfired all wy home, been to work and back today and didnt do it once. any ideas why it would be intermittent.

[E30-318is-auto]

have now replaced afm and still the same dodgy running.

[MaK-71]

Have you checked and cleaned the fuel pressure regulator / idle air stabilizer / oxygen sensor /intake air temp sensor / main fuel filter and checked for carbon deposits on the fuel injectors.

Give em all a good clean and inspection

Hope this helps MaK

[E30-318is-auto]

oxygen sensor /intake air temp sensor where o i find these.

[E30Gheko]

I have a 318i but I've not had it for very long so I don't know a huge amount about these motors yet. If this was on my 325 I'd proceed along the following lines....

I'd start with the rubber air intake hose. If it's split (happens with age) it could cause these sort of problems. It's the big black one inbetween the air box and the intake assembly.

If there's no signs of a hole in it, then check the AFM. (Air Flow Meter). Simplest way to do this is to take off the air box, stick your head so you can see in the big hole where the air box was and rev the engine. A flap inside should open freely with the revs. It may stall without the air box on so its handy if a mate can rev it for you, or just be very quick!

The air intake temp sensor should (I think) be visable when you have the air box off. It's mounted on the AFM opening. Check for any crud built up on it.

It may also be worth checkin ur fuel pump relay and the fuel pressure regulator.

[E30-318is-auto]

hmmm got e thinking about the air intake hose it is actually split right by the jubilee clip on the afm, could this be the problem i wonder, i have replaced afm so i`m pretty sure its not that, but as someone mentioned earlier in thread about plugs i did buy bosch super 4`s could these be a bad choice?

[E30Gheko]

hmmm got e thinking about the air intake hose it is actually split right by the jubilee clip on the afm

I'd say almost certainly this will be ur problem. If you very carefully remove it without splitting it further, you should be able to get a reasonable seal on it by stretching some insulation tape all the way around it provided it's not too far gone. Not a permanent fix by any means but should cure it for long enough to get a replacement delivered. An improvement in performance would also confirm whether u've found the problem or not.

Put an ad in the wanted section and you could have a cheap replacement in about 3 days.

[Brianmoooore]

If the air hose is split, it's going to run weak, not rich. Would still misfire though.
The 4 electrode plugs are not a good idea. These engines run best with ordinary single electrode plugs, the same as they left the factory with.
How come no one's mentioned the blue temperature sensor yet?

[E30-318is-auto]

just been out again and it seems the longer i drive the worse it gets, swapped my plugs back but that didnt seem to help either. its running so rich its fouling the plugs in minutes, what causes over fuelling?

[E30Gheko]

Have you done anything with the hose yet?

My 325 used to drive worse the further I drove it. The problem improved massively when I cleaned the points on the fuel pump relay. I have a replacement relay but as the car is not currently on the road, not had a chance to check if it's cured completely yet.

[Supafly]

ahem....

You wanna check your blue coolant temperature sensor mate.

I think I've read its under the inlet on the 4 cylinders??? Not sure but if you have a quick search it'll tell you where.

There we go, all mentioned now

Seriously though, it's one of the first things to check, especially if the cars running rich. If the sensors telling the ecu it's cold it will continue to run rich.

[E30-318is-auto]

ok so what do i check on the sensor. oh and yeh i taped up the split in the hose and it made no differece hehe.

[anisotropy]

If you search you should find a test for sensor. You can remove it, test resistance with a multimeter whilst cold, then put it in hot water and test again. The resistance should increase (or decrease I don't remember but I'm sure a search wil help this). You can just buy a new one from euro car parts or german swedish french car parts and stick it in -only about a tenner.
What's your fuel economy like? Are all spark plugs fouled the same? What's the cars performance like?

[E30-318is-auto]

fuel economy is terrible lately, all plugs are fouled the same and performance is very much decreased.