Rich/lean/something else? Please help!

[DanTheDoc]

Evening!

I've had a problem with my car since I purchased it just over a year ago. I'm going to give you as much detail as possible without trying to put in my diagnosis so I don't bend your thoughts.

Firstly, the car is a 1989 318i M40 auto touring.

Basic problem: it's burning something other than the correct amount of fuel and smells a bit.

Symptoms:

Since I bought the car, it's smoked a bit on start-up, more than it should in my opinion. The smoke is whitish and it clears up when the engine is warm but it can be quite a lot, increasing with revs.

The exhaust smell (at least I think it's coming from the exhaust) is strong, either rich or oily, I can't really work it out. It's mostly recognisable in the car when reversing or stationary. I can pull up at home and still smell it when I've got to my front door!

The mpg has recently dropped quite a bit. I used to get close to, if not more, than 300 miles per tank, it's now more like 240 - 250.

The revs at idle hunt slightly but nothing major, can't really see the needle move but you can hear the engine. It sits between 800 and 900 rpm.

I've recently changed the radiator and thermostat and the temperature sits between quarter and half (closer to quarter, and it is an 88 deg C stat). And if I'm not mistaken, I'm sure since the mpg has dropped, the engine is getting to temperature quicker, I may be going mad!

Recently fitted new (second hand) full exhaust, not including manifold. Also fitted new wheels, gone from 14" to 16" (not sure if this will affect mpg?!)

The one fault I do know my car has is the air filter to throttle body rubber boot is slightly split, not bad and it doesn't seem to make a difference if the split is covered. I'm on the lookout for a new one, does anyone know where to buy new?

Does anyone know where to start looking for the above fault/s? I have a few ideas but I want to know what the people with more knowledge thing so I don't waste time/money.

Any help would be much appreciated.

Thanks in advance

Dan

[DHFiS]

Engine would get to temp slower if your old stat was stuck open.

The split rubber hose will be available new from BMW. I would replace any hose which looks cracked before making any other changes.

Has the plastic bung been removed from the AFM?

[bmw9818]

my one had a petrol smell coming from the engine bay the rubber hoses were perished, and it was leaking and gave bad mpg, check those while your at it,

for some reason mine was the same it stopped 1/4 temp, but took a while to get up to temp,

try checking the blue temp sensor as that affects mpg and can leave your ecu in start up mode iirc dumping excess fuel,

[kam-325i]

Engine would get to temp SLOWER if your old stat was stuck open.

Fix'd !

[DanTheDoc]

What rubber hoses are you referring to bmw9818?

The old stat was sticking closed, used to get quite warm before the temp came back down. The stat change was a few months ago too, before my imaginary engine temp getting warm speed increase.

I will order a new hose and check that plastic bung. What would it mean if it was missing?

Thanks

[soul4t]

I would have thought that a thermo stuck open would prevent it getting up to temp quicker as it opens when it gets to the half way mark or thereabouts on the gauge?
Either way, the normal op temp is around the half way mark...mine was running just after the 1/4 way mark for a year or so before I realised...changing the thermostat sorted it, so I'm surprised yours sits there even after having a new one...unless it's faulty

Definitely get that hose replaced before going any further!

The fuel lines that are most common I believe...are under the upper part of the intake manifold...you should be able to smell an obvious leak...but I've found a slow one only when I removed the upper part when changing the gaskets!...then again, this isn't likely to cause an overfueling problem, but is well worth sorting if there's a problem as you would be loosing excess fuel!

If the bung is missing (anti-tamper plug) it may mean that someone has blindly changed the CO idle mixture screw that it protects, this could have been richened up and cause higher mpg...especially if you spend time in traffic!

[DHFiS]

Engine would get to temp SLOWER if your old stat was stuck open.

Fix'd !

[DanTheDoc]

Is this the rubber bung you're talking about, if so, it doesn't look like it's been touched at all:



This is the split in the intake pipe, the blue line shows roughly how long it is:



A few more questions I have are, what is this thing arrowed because the pipe leading to it is slightly crimped (the rough line of the pipe is the blue line, a closeup picture is below):




I'm also in the process of reducing my signature pic as it's mahoosive!!

Thanks

[DHFiS]

This is the screw that should be covered with a plastic bung. If its missing then someone has altered it. The split hose should be replaced.

The thing with the arrow in the 3rd pic is the idle control valve.

[DanTheDoc]

Ah right, thanks for that, I'll check ASAP.

Does it matter that the hose to the idle control valve is slightly crimped?

[soul4t]

That hose to the ICV looks a bit strange...my hose goes from a small (ish) plastic elbow which sits into the large hose (from Air Flow Meter to Throttle Body), to the ICV underside. This hose is sort of fused to a different pipe that goes from the TB to the Engine block (I think)...see no. 10 in this diagram:

http://www.realoem.com/bmw/showparts.do ... g=13&fg=15

See if you can have a look at it, if it looks ropey, it might be one to replace also.

FYI when ever I've ordered parts from my local dealer, the part numbers on realoem.com are usually correct! Let us know how it goes!

[DanTheDoc]

Thanks for that. From what I can see, the hose that's been fitted to my car looks like a bog standard hose from any spares shop without the little hose joining it. I'll try and have a better look.

I'm slightly confused with the little pipe location, where does it go to?

Thanks for the help!

[soul4t]

Hmm, yea worth having a closer look...it's a bit awkward as it's hidden somewhat under the intake! The little pipe goes into a connector and pipe which goes to the back side of the engine block...a hose then leads into the firewall, presumably to the heater matrix? it's no. 11 on this pic:

http://www.realoem.com/bmw/showparts.do ... g=11&fg=35

If someone has fitted a seperate hose for the ICV, then unless they have put a different small hoses section in for the coolant, there should be a hose sitting there not connected...if you follow...

No probs!

[DanTheDoc]

Ah I see. I'll have a poke around later, there is another hose there so they may have just connected two instead of the OEM one. I'm guessing they're connected for some sort of heat transfer?

Thanks again

[DanTheDoc]

Or connected for no reason but tidyness...

[soul4t]

Yea, could be something to do with heat transfer...really not sure though...and yes possibly tidyness!

[Speedtouch]

Before touching anything, I would carry out a compression test on the cylinders to ensure all are giving similar readings - anything above around 150 psi is OK.

This will establish the basic health of the engine. Any obviously low readings indicate either worn bores/piston rings, a head gasket blowing or burnt out valves.

Excessive white smoke usually indicates head gasket problems - does it use coolant, or get any oil mixing with water, and what mileage has it done?

[DanTheDoc]

Hi,

It doesn't use any coolant and the oil shows no signs of contamination.

It does use a fair bit of oil though but there are signs of leaks.

The car has done 70,000 miles (confirmed) however, the cam belt snapped when the garage I bought it from were using it and they replaced the head so I don't know how many miles the head had done or what condition it was in. That was at about 57,000 miles (what it was at when I got it, one old lady owner from new). I spoke to the old lady's husband who said he gave it to the garage at 53,000.

Do you think a garage would do a compression test if I just drove in or is it a booking type thing?

Thanks

[soul4t]

Couldn't say for sure if a garage would have to book it in...depends how busy they are...you can buy a compression tester for about £20 which might be what they charge you usefull bit of kit to have!

[DanTheDoc]

Ah right, I'll look into that! Thanks

[Speedtouch]

I recommend the Gunsons type, such as this one:

http://www.ebay.co.uk/itm/gunsons-hi-ga ... 3ccbc5b862

I've owned one for 20 odd years and it still works well.

[DanTheDoc]

Right, small and quick update.

Had a good look around and the pipe I have to the Idle Control Valve is the correct pipe with the second pipe fused to it. This is all as per OEM with the exception that it is slightly crimped. I think it's been fitted the wrong side of another pipe.

Also had a look at the AFM, the anti-tamper bung is definately missing from the mixture adjustment screw so this could possibly well have been fiddled with.

Is the best way to sort this by putting it on a gas analyzer? Also, is it just the screw that needs to be adjusted or does it need to be adjusted in combination with something else?

Hopefully new AFM pipe sourced.

I'll get a compression tester ordered as well to check my compressions. Is there a how-to on here because everything I've read contradicts each other (all spark plugs out/just one out, throttle open/closed etc).

Thanks again everyone!

[Brianmoooore]

Is the best way to sort this by putting it on a gas analyzer? Also, is it just the screw that needs to be adjusted or does it need to be adjusted in combination with something else?

It needs to be adjusted after everything else is in A1 condition. That's why it should never be touched.
If your engine has an inlet side air leak or worn injectors, for example, then making the mixture richer with the screw will improve things, but then, when the air leak is eventually cured or the injectors rebuilt, the mixture will be set too rich, so the engine still will not run right.

everything I've read contradicts each other (all spark plugs out/just one out, throttle open/closed etc).
!

All plugs out, throttle wedged wide open.