E30 Zone

I had my M20 engine rebuilt earlier this year due to oil burning caused by bad stem seals.

I had the head completely reworked including new guides and stem seals etc, the block measured, honed with new piston rings.

Running in method was to run it purposely for the first 10/20miles and then easy, I have now done around 900 miles (used mineral oil for the first 500miles and now using semi).

I was aware that there will be some initial burning of oil during running in period however I have noticed that occasionally I get the odd cloud of blue smoke?

It’s very random when it happens when driving but I haven’t seen any during morning start up that could suggest it’s the stem seals.

The engine starts and idles fine and I can’t be any happier in the way its runs.

The other day I inspected the throttle body and there was oil present in the throttle body and the AFM rubber boot?

I also pulled out the spark plugs to inspect the tips and from the below pic they seem to be fine however there is some oil around the threads?

Anyone have ideas in why there is oil in the throttle body and on the spark plug threads and most importantly what could be causing the odd cloud of blue smoke?

Sounds like blocked breathers to me, or some kind of breathing issue at least.

If you take the oil cap off when its running does it puff air out like a fat man going up hill?

If the engine is pressurising the crank case then a huge amount of oil heads up to the throttle body and then into the engine.

From what I understand there are two ventilation pipes: rocker to throttle body and the crank case to inlet - is it just the matter of checking whether these are blocked?

Is there anything else that could cause breathing issues?

Will check the air pressure from the oil cap and report back.

Well only other thing is wayyy to much blow by and that's a bit more serious.

From your plugs though they look reasonable so unlikely to be more that a bit of breathing.

Are they the plugs it was run in with?

Has the breather etc been cleaned out since running in?

Could be just left over from running in.

Best to eliminate the obvious first.

so I checked the oil filler hole, its hard to establish where its puffing air out because of the air moving around from the radiator fan. however I would say no I don't think there is airing puffed out.

if it was puffing out air what would that indicate? blow by?

they are the original plugs that I used in the engine before the rebuild, i just cleaned and re gapped them when it came to firing it up. that pic was taken around when the car had done around 6/700miles.

nope the breather pipes havn't been cleaned out yet...

come to remember when I was installing the inlet I had difficulties fitting the crank case to inlet pipe (with the spring) to the inlet etc. I had to do this a couple of times before thinking everything was fine. could the washer or o ring got disturbed and not seated properly?

the solid pipe is just the return from the head.

Agreed about the fan making things hard.

Whack a set of fresh plugs in gapped correctly and give it a week. See how they look then.

A lot of that could be left over.

Are you sure its oil smoke?

Thanks for the advice on this.

Ill try putting in a new set on plugs in this weekend and clean out the breather pipe, TB, and AFM boot pipe and see the outcome a week after.

In regards to the oily threads on the plugs this could be due to the rocker cover gasket - so ill swap this out for a new one.

If the symptoms are still present I'll try loading a video clip of the smoke.

If you suspect a rocker gasket leak then that's 100% where the oil on the plugs is coming from.
Any leak on that side leaves a swimming pool of oil in the plug holes.

The plugs don't look that bad, see how it goes.

Check your inlet manifold plenum as well, you can end up with a lot of oil collected in there.

why not just check compression's while the spark plugs are out, do this when engine is hot

I should have also mentioned , hopefully you did not break a oil scrapper ring

A ring problem would/should show much sootier plugs.

left work a bit early today so when I got home I started to investigate the potential oil issue.

first removed the breather pipe from the throttle body and seemed to be dry at this end.

I then cleaned (wiped) off the excess oil build up in the throttle body and afm rubber boot pipe, quite minimal build up but thought I clean it anyway.

next I removed a couple of spark plugs and noticed the below:





looks like the rocker gasket needs replacing which is allowing all this oil in.

ive ordered a new set of plugs and gasket which I will change this weekend. ill also remove the breather pipe and inspect for build up.

really hoping that the gasket / plugs will solve this issue.

Bit of progress since last update.....

Replaced the rocker cover gasket and checked the rocker cover for any gunk build up and all is fine.

Checked and cleaned the rocker to TB ventilation pipe and again all fine.

Replaced the spark plugs with a set of new ones and with just over a weeks worth of driving (approx 200miles) the below are the condition of the tips on the new plugs today:





Carried out a compression test and all pistons are around 240-250psi.

To be on the safe side I also checked the blue temp sensor for over fuelling issues, readings as below:

From ecu cold 3360ohms
From sensor cold 3350ohms

From ecu hot 0250ohms
From sensor hot 0250ohms

When the car is idling from initial start up I put my hand near the exhaust and noticed that there were black spots/deposits left on my palm:



After the engine warms up it doesn't seem to do the same.

As I mentioned in my original post, the whine runs and idles great and have no issues with that, it's just smokes occasionally and when reving the engine.

I'm trying to load a video of the smoke from the exhaust but any advice/help in diagnosis would be great help.

video clip of smoke on cold start up (mind the fan belt squeal )

m20 smoke on start up:

smoke during normal temp and engine rev'd:

m20 smoke normal temp:

Hi, i am no expert but 240-250 PSI seems to high i stand corrected, did you take out all the spark plugs first they say that is the proper way also did you take out the fuel pump relay or the fuse as this can effect the reading because you get an injection of fuel each revolution of the engine and it effectively increases the compression ratio.

Ok, no way you should get that after a week, something is certainly up.
Having done a plug chop on mine after about 200 miles they still look nearly new (identical plugs)

What oil are you using? I have found mineral oils to piss out everywhere as the oil gets pretty warm on these.
Duckhams classic was the worst think I have tried, lubricated the plugs and engine bay more than the engine.

Hi i tried to open your video but it say private it could be my setting, on your latest write up you do not mention blue smoke you mention black spots now, i would say getting a little black spots is normal.

chippy1947 wrote:Hi, i am no expert but 240-250 PSI seems to high i stand corrected, did you take out all the spark plugs first they say that is the proper way also did you take out the fuel pump relay or the fuse as this can effect the reading because you get an injection of fuel each revolution of the engine and it effectively increases the compression ratio.

All spark plugs were removed before i done the compression test and engine was cranked from the diagnosis plug.

HairyScreech wrote: What oil are you using? I have found mineral oils to pee pee out everywhere as the oil gets pretty warm on these.
Duckhams classic was the worst think I have tried, lubricated the plugs and engine bay more than the engine.

For the first 500miles I used mineral oil 15w 40 (first set of plugs), Im now using magnetic 10w 40 semi synthetic with the plugs in yesterdays pic.

Ive updated the youtube clips to be public now.

chippy1947 wrote:Hi, i am no expert but 240-250 PSI seems to high i stand corrected.

Indeed, around 160-180psi is more normal.

Was the test carried out with the engine warm?

Speedtouch wrote:

chippy1947 wrote:Hi, i am no expert but 240-250 PSI seems to high i stand corrected.

Indeed, around 160-180psi is more normal.

Was the test carried out with the engine warm?

I missed this detail the test was carried out cold.

As the all the cylinders gave similar readings when cold would it make much difference if the were tested warm as we know cold readings were more or less the same?

Probably not a vast amount of difference, assuming the test was carried out in reasonably warm conditions.

Were the standard pistons re-used?

Speedtouch wrote:Probably not a vast amount of difference, assuming the test was carried out in reasonably warm conditions.

Were the standard pistons re-used?

yes. I did not change the pistons, here is a pic of one of them:

she smoked like a bitch when you left gaydon the other week which to me would suggest rings without reading whats been said

what piston is that 2.7 eta?

gromgsxr wrote:what piston is that 2.7 eta?

Yeah 2.7 eta pistons.

What's people's opinion regarding the smoke colour based on the below video clip??

just a thought did you separate the piston ring gaps

chippy1947 wrote:just a thought did you separate the piston ring gaps

Yep at At 120degrees.

Looks like blue oil smoke - does it use oil?

Piston rings in the correct way up?

(there is a reason why I ask this )

hennared323i wrote:Piston rings in the correct way up?

(there is a reason why I ask this )

You and many, many people have done this. I will admit to having nearly done it myself.

What is the oil consumption?

How is the fuelling set up?

Is the oil smelling of fuel?

That smoke is certainly hydrocarbon smoke, either fuel, oil or both.

I'm certain the when I built the pistons I took particular care when putting on the rings top side up.

Oil consumption was there initially during the break in period however I dont believe this is the case now after by doing miles.

I've started to think that this maybe down to a fueling issue caused by the ECU and head setup.

I was playing around with the FPR last night and the fumes were really bad (fuel smell) by the time I went back in I was high. The car is backed up near a wall and i can see that it has left black soot where the exhaust is pointing to.

I'm going to get the engine tested for emissions tonight but I don't believe this will resolve the issue

Could the stem seals cause this much smoke?

Not if you replaced them; worn valve guides can cause alot of blue smoke though.

Which ECU and chip are you using?

If your burning oil then you should find you oil level going down.

A friends cosworth rebuild was smoking in a similar manner the other month (turned out to be a cracked ring) and that was using about 1l every 50-70 miles.

If your smoking that much then your using oil fast.


I am wondering if it could be fuel related as well.

Does the oil smell like fuel if you pull the dip stick?

How has the fueling been adjusted for the 2.7?

What ECU set up are we talking about?

Whats the full engine spec? (ETA bottom end, early 885 (325) head?, 325 inlet and exhaust?, Cam?, I am guessing you have an adjustable pressure regulator? bad news those.)

The engine in question is supposedly a Hartge H27 setup with ECU. I can confirm that the ECU is genuine as it has markings around the case and that the chip is heavily glued into place (trademark). Can confirm ECU number later tonight.

When carrying out the rebuild I released that the cylinder head (885) was in fact a standard 325i head/cam setup with inlet and exhaust however the crank and pistons are from an ETA 2.7. The head was sent to Correy's Cylinder heads to be worked.

When I originally purchased the engine it came with one of those FSE FPR which I swapped out for a 3.0 bar 325i regulator.

I am assuming the person who had the engine before me may of had an issue with the original Hartge worked head (cracked, warped etc) and may of swapped it for the standard 325i head.

This leads me to believe that now the ECU/chip will cause over fueling issues as it would be expect a longer duration of cam lift but in fact is stand with the 325 cam? Could this be the case?