Mi16 Idle "chug"

[timmsy19 3]

Hi all

 

got a strange one here.

 

got my idle control valve issue sorted a while back which means car now idles dead on the money.

 

however at idle it chugs a little... bit like the revs are going up and down ever so slightly. Im i just being paranoid or does this mean something isnt running right. ive tried the screw on the AFM but that does nothing.

 

went thru MOT fine with it so cant be exhaust really. although im paranoid that my manifold has a slight crack in it.

 

anyone have this?

 

any ideas?

[jackherer 543]

Worn throttle body probably, try gently nudging the link between the two butterflies when its chugging and if it suddenly purrs you've found the culprit. They are all knackered these days I am finding.

[Simes 248 2 Cars]

Mine does this and so do lots of others - I've even noticed different fuels (all 95) can make a difference with the idle.

[jackherer 543]

Mine does this and so do lots of others - I've even noticed different fuels (all 95) can make a difference with the idle.

 

If everything works properly an Mi16s idle should be very stable.

[Simes 248 2 Cars]

If everything works properly an Mi16s idle should be very stable.

 

 

Forgot to add I've got different cams.

[Ethos 0]

My idle is VERY steady on the mi16 but it still "chuggs" a bit, especially noticeable if you listen to the exhaust!!

[jackherer 543]

My idle is VERY steady on the mi16 but it still "chuggs" a bit, especially noticeable if you listen to the exhaust!!

 

If it chugs (and you have a standard cam ) the idle fuel mixture is wrong, either because the screw on the AFM has been played with, or if adjusting that screw wont cure it, there is either a slight airleak somewhere (like a breather hose or the oil filler cap/pipe) or the throttle body is worn.

[Ethos 0]

I *think* the oil filler pipe might have a slight air leak now you mention it, although I think it runs a bit rich on idle as I can smell petrol very slightly.

 

Hasn't bothered me much, just on my list of things to do at some point

 

Guessing getting the idle mixture set wouldn't cost a great deal, although i'm not entirely sure how they set it- ie what level it should be.

[timmsy19 3]

right so check the butterfly and for air leaks. cheers

 

ajusting the screw on the AFM doesnt do bugger all. just seems to spin round both way neither losening or tightening

[James_m 0]

right so check the butterfly and for air leaks. cheers

 

ajusting the screw on the AFM doesnt do bugger all. just seems to spin round both way neither losening or tightening

 

It does eventually! Keep going and the engine noise/smothness will change depending on the mixture change.

My car also chugs and smells of petrol, though i do have an inlet cam, but im pretty sure it was almost the same with the standard cam.

In my case, i think the entire engine management system is just generally old and worn out.

[timmsy19 3]

right will have ago on lunch tomorrow me thinks

[Veero 1]

Right just got my Mi running again after another 9 months of it sitting around.

 

Before I put it away last time it had a horrible habit of roaring up to 2500 revs on start before sometimes settling down and sometimes not. Changed over the TB and noticed that the replacement is considerably less worn than the old, also swapped over the ICV. So now it starts and I've adjusted the idle to just under 1k but it chugs a lot. I had a fiddle with the idle mixture screw and couldn't get it spot on. It seemed to almost get there with the chugging but then would start struggling and sound like it was on the verge of cutting out. This AFM BTW was a reconned one thats had 9k miles of use. Tried another older AFM and it's exactly the same. Just can't get it right. Tomorrow I will have a look at how badly worn the TB linkage is and see if Jack's suggestion helps find that sweet spot.

 

Otherwise is there anything else that can affect the idle and chugging like this?

[timmsy19 3]

Right just got my Mi running again after another 9 months of it sitting around.

 

Before I put it away last time it had a horrible habit of roaring up to 2500 revs on start before sometimes settling down and sometimes not.

 

mine seems to do this every time i start up but always settles just under or on 1k after a few seconds. had replaced the ICV with a good working one and nothing changed so iv put that down to a cold start

 

unless its not meant to do that?

 

anyhow going to out to take a look a TB will report back

[jackherer 543]

A high idle is another symptom of a worn throttle body.

[MikeT 0]

My mi16 idles perfectly / smoothly from cold but when warmed up chugs like a good un' but its bang on 1k - if you get to the bottom of it I'd be interested to see if its the same fix on mine.

 

Had people say "thats running rich" or it "sound like it running on 3 cylinders" when its chugging! :s

[nick 3]

Just out of interest..... which way up are your afm's mounted?

 

Nick

[timmsy19 3]

mine is mounted withplug comng out towards bonnet with the black box towards the front of the car.

 

what difference could this make nick?

[nick 3]

Try turning it round, with the plug to the bottom. I had issues with mine (I'll find the topic when I have time) when it was mounted the same way as yours.

 

Nick

[Phil H 16]

I have noticed mine does this too, although as it has not run for nearly two years, I will see whether it settles down after some use. My AFM is located flat, so will rotate to try to see if any improvement.

[KRISKARRERA 2 1 Cars]

One thing I get with mine is terrible throttle lag and general jumpiness coming on and off the throttle. And with small throttle openings it tends to feel like the throttle plates are flapping about cutting and reintroducing fuel over again many times a second.

[timmsy19 3]

One thing I get with mine is terrible throttle lag and general jumpiness coming on and off the throttle.

 

see i get that exact same thing. it never just wants to gradually build up speed slowly but then i thought that might be something to do with the egernes of the engine

 

im thinking that i have 2 issues,

 

1: AFM mounted incorrectly

2: TB faulty

 

a combination of problem 2 and 1 is causing the first issue. the second issue just comes along with part of issue 1 if the TB is fubar'd

[jackherer 543]

Thats another symptom I've seen with worn TBs, when you blip the throttle in neutral from idle it can hesitate, bog down and even stall whereas a fresh TB will let you blip the revs in very short sharp bursts.

[Veero 1]

A high idle is another symptom of a worn throttle body.

 

Oh it's not a high idle, just when you start it it roars up to 2.5k sits there for a second or two then drops down to idle at around 1k fine. No idea why it does it.

 

As for the AFM mine is mounted flat with the plug coming out backwards heading towards the bulkhead.

 

As for a worn TB, is there anywhere to get a decent TB, does anyone sell them new? There's plenty on ebay (those polished ones promising 6hp more power make me giggle) but I suspect they're all as worn as mine. Which model VAG ones fit?

[jackherer 543]

I think Golf Mk2 16v and possibly Audi 2.8 V6 are a source for TBs. Alternatively a 306 GTI6 inlet mani and TB fits. Either of these requires a bracket to hold the throttle switch.

[KRISKARRERA 2 1 Cars]

Which bit of the throttle body gets worn then? Just thinking maybe there's some way to fix it.