Mi16 Hot Idle - Total Stall. Usual Remedies Tried. :(

[Jon_Bmw 13]

I signed up to the forum a couple of months ago when I was on the look out for an mi16. Finally got a project one, which is turning into a bit of a disaster. Next time I will definatly buy a running good one.

 

It hadn't been run for about 2 years and some of the wiring was a bit dogey/wrong. Its a joint project between me and my brother and luckerly he is a wizz at electronics, compared to me anyway. After sorting out the injectors it eventually started, the rev counter was INOP but he soon sorted that. It was missing on 3 but it was sorted by pushing the inards of a ht lead back to where they should have been.

 

Various other problems/gremlins were sorted as well.

 

The PROBLEM: The car runs ok on cold idle, with a very intermitant miss on occasion(once over 1 min or so). As it warms up( 3-5 mins) it starts to run a bit lumpy. The temp gauge is now showing a quarter. Gradually the car idles worse and worse although it will rev up fine. Once it reaches full operating temperature and the fan has cut in once or twice it chuggs to a total stall. It then will not restart properly at all till about 35-45 mins has elapsed(when its cooled down basically)

 

Things tried:

 

Brand new COIL

 

A spare ignition module that is swapped in once it has got to its stall stage. (not new)

 

Fuel pump relay

 

Fuel Pump

 

Coil Lead

 

 

Things Tested:

 

Engine temperature sensor - within normal boundaries.

 

Crank sensor - we think that is in range(checked on an ossiliscope)

 

 

Other things noted:

 

Oil pressure gauge reads a half at all times really, so i think that might be a sensor-->gauge issue.

 

 

 

Sorry for the long post and a first post from a newbie asking for advise.

 

 

If i think of anything else relevant i'll post it up.

 

Cheers guys

 

 

Jon

[pugman211 0]

Sounds like it could be the ignition amp (even though you have changed it) or possibly the ECU temp sender. Only other thing i can think of checking is that the SAD is working properly etc.

 

As for the oil pressure, mine always stays on half way till the engine is warm, then goes down to quarter mark, but mine is a brand new sensor.

 

Are you running Mi Motronic or Jetronic?????

[Jon_Bmw 13]

Well as you probably know the usual cause of problems like this are either the coil or the ignition module heating up. So once its in its stall stage we tried switching to a "cold" ignition module(the spare) to no avail. Its like a switch as soon as it reaches a certain temperature it just refuses to run.

 

As for the temp sensor, resistance readings taken off it appear to be in the normal parameters. We have even tried placing various 'right' specced resistors in the temp sensor wiring to trick it. No luck.

 

The problem is under any load condition, even on WOT it will still stall and no idle or rev so we have pretty much discounted the SAD

 

The car is running mi16/bx motronic.

 

We are starting to suspect the ECU and whatever internally fires the ignition amplifier.

 

Thanks for your post by the way, good to see a response so soon.

[Jon_Bmw 13]

Any ideas guys?

[brianthemagical 1]

try some of those inline lad things for the spark plugs to check if it is the spark/what it's doing. or try an afm

[kyepan 291]

I've got a car that won't start when its hot, it was fine before but started misbehaving at some point over the last few months and has gradually got worse. i'm going on a hunch tonight from the sounds of your problem and am going to try something.. you might find it's the ignition amplifier getting too hot, or a bit knackered and getting too hot ..

 

mine is backed on metal but stupidly i wedged between two water pipes, which heat up, and ignition amplifiers dont like heat, i'm going to mount it properly on the inner wing when i get in... and try getting it hot...

 

crosses fingers toes etc.

[returnofjim 0]

I had a very similar sounding problem recently, went throught the usual changing of parts, ign amp, afm, etc, none of these cured it. The engine would run fine on short journeys but once it got warmed up it just misfired. It turned out to be a very small split in the hose from the icv to the inlet manifold, im not saying this is what is causing your problem but its worth checking. Take the pipe off and have a good look at it, it was only a hairline crack what caused our misfire.

[kyepan 291]

didn't work.

 

Got stranded in sanisburys last night, and per anthonys advice i used the sub cable from the battery positive to hot wire the starter and it started, so that means there is definitly something wrong with the wire from the starter negative to the fuse board...

[Jon_Bmw 13]

I thought i'd do a little update on this.

 

Still banging our heads against the wall with this one, its getting to the stage of "lets just burn it."

 

We checked compression when it was cold, with all of the cylinders reading around 13 BAR. Although number 1 (closest to the flywheel is number 1 right?) took more cranks than the others to get it up to 13psi.

 

Then we checked it warm, cylinders 2,3,4 were all about 13 bar again, but from memory cylinder 1 was down at about 7

 

OH DEAR. Popped a bit of oil in the cylinder and it shot up to 13 BAR, so we are guessing that the piston ring is a bit foobarred.

 

A theory that my cleverer brother and father have come up with is that there is a shed load of positive crankcase pressure pushing past the linings that is effectively unmetered air re-entering the car via the valve cover to inlet pipe causing it to stall once it is warm.

 

Thinking about it now, we could test this by removing the pipe and blocking off the air inlet bit and letting the crankcase breathe to atomsphere.

 

What do you guys think should be our next move? Burn the f**ker?

[pugman211 0]

sounds like a good theory!!!! Give it a go as it wont hurt to try it!!!!

 

Good luck

[Jon_Bmw 13]

Oh toss, the cleverer people have already tried it whilst i was working late one night. Bug*er!

 

Its going to be one hell of a bonfire night on the 5th

[Normski 1]

I had the same symptoms to this myself. Turned out to be a fuel pressure problem, the signal hose from the inlet manifold to the regulator was split. Something to check out.

[Jon_Bmw 13]

Cheers Normski, Just whipped the fuel pressure regulator right off to check the hose. Its all good. Holds a vacuum no problems! Bummer.

[Jon_Bmw 13]

Any more leads? Head is going to be coming off soon otherwise. And that is a sad job.

[Jon_Bmw 13]

Come on guys, help a newb out

[Guest jpward99]

Hey Jon,

 

Got mine sorted (as you know similar symptoms) - after putting in a new ignition amp, new coil, new tachy relay, new HT leads & plugs, new dizzy cap & rotor & ECU without fixing it............changed the dizzy itself and it's fixed! Including revving a lot cleaner up to the limiter.

 

It must have been a fault in the sensor/fly lead which sends a signal to the amp.

 

I picked up a 2nd hand dizzy on ebay for £30ish to try first before splashing out on a new/refurb unit.

 

Good luck!

Edited November 12, 2007 by jpward99

[KRISKARRERA 2 1 Cars]

Oh well too bad you aint got a dizzy Jon.

[Guest jpward99]

Show's what I know!

[Sandy 189]

The last one I cured had an oil breather pipe split and I replaced it, which made it better, but not fixed. At the next attempt I found the throttle spindle had play, so I swapped the TB and it was abso-friggin-lutely right as rain.

 

Good luck.

[Jon_Bmw 13]

JPward, you hero, well done on sorting yours out mate.

 

We think we made the breakthrough we were looking for last night. My brother got his osilliscope out last night and checked for power to the coil. Yep. Power after the coil. Yep. Power to the king lead. Yep. What we did was rev it up till it stalled each time and checked it. The above still occured. So we fitted a timing light between the HT leads and the spark plugs. Sure enough when it stalled at 3000rpm the timing light went dead straight away. So the problem is either the Dissy Cap, Rotor arm, HT leads or plugs.

 

We are betting on the rotor arm as it has a small burn mark inside suggesting it has been arcing onto the head of the engine. No Actual distributor on this as its an mi16.

 

Tomorrow we will get a rotor arm and HOPEFULLY it will drive for more than 10 minutes!

 

Wish me luck.

[Dream Weaver 2]

Good luck, the Mi16 eats dizzy caps/rotors so there is a good chance that is the issue.

[Jon_Bmw 13]

Well almost embarrased to admit it. It turned out it was a £15 rotor arm after all those nights pissing around looking for something more complex. Mind you, who has ever heard of an overheating rotor arm!!

 

Cheers for all the input lads, hopefully i'll be able to help people out in the tech section some day

[Dream Weaver 2]

When I first bought my 205 it had an Mi16 engine fitted that was blowing blue smoke - it was diagnosed as piston rings, so I knew I would eventually have to rebuild it - took it out one day and it came to a rumbling stop at which point I thought that was it, engine knackered.

 

So I removed the lump, and embarked on the project link in my sig - brand new engine etc. WHen I was dismantling the old engine, I removed the dizzy cap and the rotor arm was in a million pieces - effectively I had removed and dismantled my engine purely because of the £15 rotor and I could have kept it going for a while in reality

 

It did need doing though.