Revs drop when oil cap is removed

[Rallyprep_UK]

Hello,

a guy came to look at my 325is which was a complete runner but had rusted to death so i was breaking it. I drove the car previously and it went like a bat out of hell !

He was after the engine and I fired it up and I thought it was purrrfect.

after umming and ahhing he pulled off the oil cap and as he did so the revs changed (-100rpm at a guess).

With that he said it was F***** and tried to get it cheaper. I told him I would rather keep it as a spare and off he went.

Is he "having me on" or is there some sense in his madness ?

thanks in advance
Will

[Felix79]

would it not drop engine pressure doing that and naturally cause the RPM to drop?

[Elecblondie]

Having you on, does that on every engine I've played with.

[Rallyprep_UK]

thats what i thought which is why i told him where to go.

oh well. Its nice to have good spares i spose. I have already pinched the gbox after damaging my selector input shaft was loering the car over the engin/box when the shifter got caught and broke the bit going into the box

Is there such a thing as a high compression engine ? It came from a d reg 325is coupe

[Elecblondie]

Yes the compression was changed on them. The earlier engines are higher compression or so I've read here and while nominally the same power are normally a little more powerful.

[Rallyprep_UK]

birlliant !

thanks once again !

like your picture/car too

[Elecblondie]

Thanks, it's only a wheezy 4 pot though.

[Felix79]

Sorry for sounding dumb , what was the difference with a 325Is and a 325i sport and the 325i. I always assumed a 325IS is a 325i sport

[Brianmoooore]

Removing the oil filler cap allows extra air to enter the engine, via the breather pipe from the rocker cover, but it doesn't go through the air meter, so no extra fuel is added to suit. This results in a lean mixture, and the revs dropping.
Exactly what it's supposed to do.

[Rallyprep_UK]

how precise, i had pretty much worked out its normal to do that myself but its nice to know why also !

thank you very much

[Elecblondie]

To be honest I'd be dubious of someone still keen to buy an engine they describe as "f****d". If I thought something was that bad I'd be walking away.

[Rallyprep_UK]

yes i dont like dealing with muppets which is why I would rather keep it !!!

[Felix79]

A good kick in his nutt sack will revive all common sense and get you a good price!

[magpie]

hope he travelled to see it timewaster

[Alex]

Sorry for sounding dumb , what was the difference with a 325Is and a 325i sport and the 325i. I always assumed a 325IS is a 325i sport

there was a 325is in other countries but iirc they dont look like sports so dont know what the difference is, they just look like normal 325i

here is one

http://cgi.ebay.com/ebaymotors/Cars-Tru ... 06.c0.m245

think they might have had LSD or something

[rossco_325i]

i went to top up my 325i sport wit oil one day and forgot to put the cap back on like a MUPET!!....... the car ran really bad revs going up and down, as soon as i put it back on it went all normall ha ha sweet

[pugboy]

Could be worse. You could have someone come to look at your car, switch the plug leads over and then tell you the engine is shagged.
I told the guy to fook off, but it took me ages to suss out what he had done and then a crash course in the firing order to work out what had been switched round.

And do you know what the worse thing was - it was a crappy old Metro I was selling as a favour to my sister in law!

[323iNathan]

In America the 325is was really not too much different (save for the suspension) from a regular 325i.
In Australia the 325is is pretty much the equivalent of the English 325i Sport (but we didn't get the Tech I, just Tech II).
In South Africa they didn't get the M3 so their 325is had the 2.7L Alpina motor, 5 lug conversion, with M3 suspension (and also Tech II kit.)

[e30_Turbo]

i went to top up my 325i sport wit oil one day and forgot to put the cap back on like a MUPET!!....... the car ran really bad revs going up and down, as soon as i put it back on it went all normall ha ha sweet

Done this same thing myself, thing is my setup runs an open to atmos anyway, so I can drive all day with no cap on and never know!!

I only realised this 20 miles later when I was getting a strong oil smell into the car, opened bonnet, there is was, an oily mess. Lost bloody cap too....

That was a couple of days before the photo shoot to, wasn't a happy bunny. I've had e30's for almost 9yrs now, nothing else, so no idea why I forgot to stick the cap back on.

Still, as long as you learn from your mistakes it's all good.

Fozz.

[e30_Turbo]

[hubble]

I'll admit that I know practically nothing when it comes to these cars apart from checking the oil. I struggle even changing a bulb BUT Even I know that when taking the oil cap of it's perfectly normal for the engine to drop a few revs.

[Rallyprep_UK]

I'll admit that I know practically nothing when it comes to these cars apart from checking the oil. I struggle even changing a bulb BUT Even I know that when taking the oil cap of it's perfectly normal for the engine to drop a few revs.

thanks for the sarcasm

so unless there are others who check their oil with the engine running and from under the oil filler cap I would bet my bottom dollar that quite a few people never knew about the revs dropping.

even so, i figured it was ok and simply wondered why it does happen.

thanks for your input