Mi16 Misfire

[KRISKARRERA 2 1 Cars]

My Mi16 has developed a misfire.

 

It is present at idle and low revs.

 

If I rev the engine to say 2.5k rpm in neutral it behaves fine.

 

So far I've changed the spark plugs, distributor cap and rotor arm, and coil.

 

Could it be the ignition amp?

[luggy 13]

Is the miss fire present from cold or when its at running temp?

 

 

By miss fire do you mean it sounds like its running on 3 cylinders?

[KRISKARRERA 2 1 Cars]

Since this problem started, i.e. yesterday, I've never let is run up to full temp, don't want to risk damaging anything. But yes it's like its running on 3 cylinders.

 

I've also tried my spare ECU and spare AFM but they haven't helped improve it either. Might try a compression test now.

[Stu 18]

I'd certainly swap the amp before you try anything, i had a similar issue with a brand new (albeit spurious branded) amp, swapped it for a blue Bosch one and it never missed a beat for the entire time it was injected.

 

Ive got one if you need one too

[KRISKARRERA 2 1 Cars]

Compression test was 195, 195, 195, 170 psi. I retested that 170psi cylinder with some oil down and it then showed 220psi.

 

Thank you Stu. I'll hold on that for the moment because my old man noticed something - the exhaust sounds a bit too loud around the manifold area so I'm wondering if I had a leak or crack there

[luggy 13]

Compression test was 195, 195, 195, 170 psi. I retested that 170psi cylinder with some oil down and it then showed 220psi.

 

Thank you Stu. I'll hold on that for the moment because my old man noticed something - the exhaust sounds a bit too loud around the manifold area so I'm wondering if I had a leak or crack there

 

Which plug/s were sooted up?

 

Had a similar issue with my MI where it was running on either 2 or 3 cylinders from cold, sounded like a Trabant, whipped plugs out, cleaned them, disabled fuelling and sparks, turned her over for 5 secs to get the excess fuel out, plugs back in with replacement known good AFM and was running fine.

 

Start her up then disconnect the AFM to see if it makes any difference, if its still the same then you know then its the AFM or possibly the connection.

 

Seeing that you've already tried a different AFM, disconnect the battery for 30 mins then try again.

 

Never had an issue with the ignition amp, its always either been either the dizzy, coil or AFM causing the issues from cold, good luck

Edited October 16, 2012 by luggy

[KRISKARRERA 2 1 Cars]

Yes the plugs are sooted up but then I guess they would be with the way its running. I had both relays and spark plugs out while I was doing the compression test so everything was cleared out but still the same when I put it all back together. Will see if there's any difference with the AFM disconnected.

[KRISKARRERA 2 1 Cars]

Disconnected AFM plug - engine died. Disconnected CTS plug, ran worse, so those two are ok.

[KRISKARRERA 2 1 Cars]

I was just performing an injector test on my car. You probably know about this test but I'll explain in case you don't. Basically you ground the fault code reader socket and then turn the key to ignition position and after a few seconds the injectors should be heard to pulse. I did this and discovered that only one injector was pulsing. Obviously this result is a bit of a red herring because if only one injector was firing the engine would not start at all.

 

EDIT: Ignore the above, had my mate, who runs an injector cleaning business, test them and they're ok.

[kyepan 291]

take the air filter off with the afm connected, take something long and stiff, gently start to open the afm flap.. does it run correctly then? if so it may be the afm is dying.

[KRISKARRERA 2 1 Cars]

Yeah I'll try that. I've got an ignition amp on the way from Stu. Not much left to try, thinking cambelt next. Not looking forward to that in this grim weather.

[Miles 331 1 Cars]

A Blue Bosch one I hope

[KRISKARRERA 2 1 Cars]

I believe so.

 

Tried the AFM test Kyepan, made it worse lol.

 

HOWEVER, I've taken the cambelt covers off and I'm trying to line up the timing holes and unless i'm doing something wrong it would appear the exhaust pulley has jumped quite a few teeth.

 

Can I just check, When the crank hole is lined up the exhaust cam timing hole should be at "6 o'clock" and the inlet cam at nearly "9 o'clock"??

[kyepan 291]

not sure on the orientations from memory, but the timing pins if 6mm should go all the way through the holes in the pulleys into the head, and locate with a bit of wiggle in them, you should have even slop left and right on all three pins.

 

on the afm, try again, but this time moving the flap in the other direction, check result.

[KRISKARRERA 2 1 Cars]

Yars, I will try this if the problem remains, though I'm hoping she'll be running ok when I've finished putting it all back together with the exhaust pulley in the correct position.

 

I shall now proceed to do a forum search on Mi16 cambelt, because I'm a bit concerned about getting the tension correct.

[KRISKARRERA 2 1 Cars]

I've put it all back together and misfire gone!

By far the hardest part was getting the cover on and off.

[luggy 13]

I've put it all back together and misfire gone!

 

Good effort!

[Miles 331 1 Cars]

Hopefully with a new belt

[KRISKARRERA 2 1 Cars]

Nah it's only been on there a year, I couldn't see anything wrong with it... or am I tempting fate?

[welshpug 1,657]

should never re-tension a belt.

[KRISKARRERA 2 1 Cars]

Uh oh, time to get another then.

[Miles 331 1 Cars]

You can, But if it's slipped I wouldn;t like to use it as it would of done something even if you cannot see it, But for the sake of £25.00 its not worth the risk