325I Engine note...

[SeymourCake]

I have noticed that while sitting in my car, ONLY in idle, the engine idle has a vague judder/lumpyness within it's tone.

For example, if I am sitting in the car, I can feel the small judders. Or if I open the bonnet, I can see the these little lumps in idle in the way the engine moves while it's idling.

This is my first e30, and I haven't experianced this sort of thing in all my other newer cars.

Does anyone know what I am talking about? lol .

Just wanted to know if that is normal in all m2025b engines...

[wullie325i]

should run quite smooth but they are old now.

check all your air hoses on the afm side for leaks/craks ect and spray in that area with carb cleaner and see if the idle changes. if it does you have a leak.

[Z3I]

Mines nice and smooth, no juddering. wullie325i gives good advice..

[wullie325i]

Mines nice and smooth, no juddering. wullie325i gives good advice..

im good now and again lol

[SeymourCake]

Thanks.

However I think if it was a air leak, the juddering would be quite severe won't it? and it would run quite horrible? i have checked if there are any air leaks by opening the oil cap while engine idling, and the engine started to hesitate which is a sign that there are no air leaks (from what i been told). Also checked the big boot from AFM, no sign of any leaks.

I think the juddering I am on about is not REALLY that noticeable unless you pay attention to it. For example, say if I am waiting at the traffic lights with the stereo off, only then I can sort of feel this vague judder within the way it idles. Bit of a lumpy feel.

I think I am going to check out my idle control valve first thing when I wake up tomorrow. Or maybe need to give throttle body a clean?

[Z3I]

Check it at night too. Take it to a dark place (the car), lift the bonnet and observe, see if you can see any HT leaks to earth. No cost check.

[wullie325i]

timing could be out a fraction also but theres alot of things that give these symptoms

[JJ26]

When were the plugs last cleaned and gapped?

[SeymourCake]

Plugs were changed a few days ago. Could loose or badly gapped spark plugs cause this?

If so then I think that could be the problem as I didn't have this issue a few days ago.

[Brianmoooore]

A large air leak (such as removing the oil filler cap) will make it idle very rough; a small air leak will make it idle slightly rough.
One common place that M20's leak air into the inlet tract that doesn't seem to be very well known is via a missing or perished blanking plug on an unused stub pipe on the inlet manifold, situated just behind the throttle position switch.
Plenty of other places that there can be a small air leak of course, and there may not just be one leak.
It may be a completely different reason for the slightly lumpy idle, of course. A compression test may show if one particular cylinder isn't contributing what it should.

[SeymourCake]

A large air leak (such as removing the oil filler cap) will make it idle very rough; a small air leak will make it idle slightly rough.
One common place that M20's leak air into the inlet tract that doesn't seem to be very well known is via a missing or perished blanking plug on an unused stub pipe on the inlet manifold, situated just behind the throttle position switch.
Plenty of other places that there can be a small air leak of course, and there may not just be one leak.
It may be a completely different reason for the slightly lumpy idle, of course. A compression test may show if one particular cylinder isn't contributing what it should.

Ah I think that is where the problem lies!

The person who changed my spark plugs a few days ago said that the thread inside cylinder 1 where the spark plugs go in is in bad condition. He said if it tightened it anymore, then that the spark plug would get stuck within the messed up threads of the cylinder, and to take it back out again would be a really big job (taking the head off). So he had to leave the new spark plug in cylinder 1 quite loose. I think this is why the engine is reacting like this.

Might have to get it checked out by a mechanic tomorrow.

[Z3I]

All of a sudden it looks easy!

[SeymourCake]

Its not good news though mate...

means the heads going to have to come off to repair the cylinder 1 so the spark plugs can properly sit there, depending how bad it is ofcoarse.

So it is fair to say this problem could be the cause of the symptoms I have described in my initial post?

[Simon13]

sounds like a helicoil job, it can be done in situ though

[SeymourCake]

Cheers Simon... SOME good news.

Can you elaborate on what a helicoil job is/involves?

[Brianmoooore]

Helicoil is essentially tapping in a slightly larger thread, then fitting a special 'coil spring' in that thread, so that the inside of the 'spring' becomes the new spark plug thread.
Can be done in situ by packing grease into the cylinder with the piston part way down the bore, then turning the crank to expel the grease, along with the swarf, when finished.

[SeymourCake]

Brian can this cause the lumpyness I mentioned earlier?

[Brianmoooore]

If the plug is still sealing properly, then it won't affect running in any way.

[SeymourCake]

I reckon the cylinder 1 spark plug is not sealing properly.

Also bad news... I just came back from the garage, the mechanic said nothing can be done about it, except shut the head down and get another cylinder head.

Not happy at all.

[Brianmoooore]

Why does he reckon it can't be helicoiled?

[SeymourCake]

I don't really know.

He said it will make the thread inside bigger, therefore making it useless for a sparkplug to fit into. Also something about it being alluminium so you can't do nothing to it.

Then again... He could have just said that because he doesn't want to do the job...

[powelly]

I don't really know.

He said it will make the thread inside bigger, therefore making it useless for a sparkplug to fit into. Also something about it being alluminium so you can't do nothing to it.

Then again... He could have just said that because he doesn't want to do the job...

he obviously doesn't know what a helicoil is then, essentially you drill the existing hole oversize, the new hole is then tapped to receive the helicoil, the helicoil is wound in the the freshly cut thread restoring it's original size, you can use it in any material, steel, aluminium or whatever, I know a guy that uses them on his 600hp Ford Falcon racing car, sounds like your mechanic wants to fleece you or just doesn't know what he's talking about.

[e301988325i]

sounds like your mechanic wants to fleece you or just doesn't know what he's talking about.

here here.

My idle did this M20B25, my TPS wasn't registering idle, it got a lot smoother when I fixed that and when I reset the valve clearances it also improved the smoothness of the idle. Obviously get your plug helicoiled first though.

[SeymourCake]

Yeah the guy is a knob tbh. It's clear now that he didn't want to help me at all.

Anyway I have checked the spark plug in cylinder 1 properly, and it seems to be sitting in there alright! I actually think it IS sealing properly. It's just a little bit looser then the others, but still sealing properly in the cylinder.

I am thinking I should just adjust the valve clearance now, and make sure that my TPS is working like e301988325i suggested.

Had a look at the valve clearance tutorial, and don't feel to confident doing it myself, so I will take it to someone who knows what they are doing and see if they can do it for me.

I could try and record what the problem is on my phone, however the judder and lumps are so faint that I doubt the camera will pick it up. It's just when you sit in the car, or see the engine block while turned on, you see it shake a little bit while idling.

[SeymourCake]

Thanks for a reply mate. Just wondering where around the leads would be a good place to plug in the multimeter to test it?

[Ilkorin]

interesting...had the same problem myself, the idle would roll a little bit and sound slightly uneven.

An air leak check has done it wonders but it isn't quite 100% - I would say check and double check the air leak problem... Will keep watching the thread though, might do the HT lead check when I have time...

[SeymourCake]

Sorry forgive me for being very dumb but I'm finding that the mulitmeter won't read anything because of the leads have a rubber casing around them. Don't really know where to plug in the crocodile clips to check the ohm rating..