Forrest 35 Report post Posted July 19, 2009 (edited) So have had the m20b25 about a month, and have noticed the idle getting progressively worse and more rotaryesque as I have had it. In the weekend I took the valve cover off to paint it, and after replacing it this morning it is a lot worse. The motor has a pod filter which didn't make any difference to the idle when I fitted it. There are a few things I can think of to fix it and answer my own question, but other advice or pointers is entirely welcome. So my car is the early Motronic 1.1 (if that makes any difference). At idle it's only idling at just under 500rpm (is this normal) but the rev counter is jumping up and down more than I had noticed before. From my previous e30 my problem spells out vacume leak, but I am not so sure, 6 cylinders are scary. My thoughts: - Intake boot is starting to crack but hasn't split. - The valve cover may have got some paint inside it (when I painted it this weekend) where the top hose under the throttle body goes. - I need better hoses for my pod filter to AFM. - I don't think the idle control valve/screw has been touched (definitley not by me but maybe previous owners. - Something else? (Insert knowledgable mechanical opinion here) Since I am a bit of a noob at m20's, my mates 320i has the same problem so some help is doubly appreciated. I have only had the car less than a month so please bear with me. Probably should have searched but the forum is quiet this morning so give someone some work to do - Nathan Edited July 19, 2009 by Forrest Quote Share this post Link to post Share on other sites
Mark 178 Report post Posted July 19, 2009 Should be idling at 750rpm Does the engine always idle at 500rpm when cold? Or only when warm? Quote Share this post Link to post Share on other sites
melowpuf 19 Report post Posted July 19, 2009 Sounds like an air leak, or ICV needs a clean.. when you put the rocker cover back on, what condition was the gasket in? did you tighten the breather hose on top of the rocker cover under the manifold? They would be about the only things you would have disturbed when you took the rocker cover off. Check those and then pull the Idle Control Valve off. ICV picture - Item 3 in the picture Spray some carb cleaner into the inlet and outlet of the ICV and rotate it quickly so you can see the mechanism inside turn. keep doing it till the inside moves quite easily, these build up lots of gunk over the years and need a good clean out. sometimes you may need to spray carb cleaner in it and then poke your finger in to rotate the inside bit to help get it moving. You should be able to make that inside bit move quite freely by just giving it a quick turn in your hand. bolt it back on and see how you get on.. that has worked some magic on oh so many m20's I've worked on over the years. Quote Share this post Link to post Share on other sites
Forrest 35 Report post Posted July 19, 2009 (edited) Thanks a lot Melowpuf, rocker cover gasket looks is great condition, going to repaint the cover anyway looks like balls so I will recheck it tonight. Mark it slowly creeps up when warm to just over 500rpm Edited July 19, 2009 by Forrest Quote Share this post Link to post Share on other sites
