Jerky On Low Throttle And Coming Off Revs

[Veero 1]

So on the Mi coming off throttle onto idle doesn't happen instantly, instead the revs drop off throttle and then lazily come down to idle so there's lots of overrun and low speed driving say for the speedbumps on my road is a royal pain in the backside. It's like the ICV is wide open and doesn't shut fast enough to actually slow the car down. No air leaks as far as I can tell.

 

I have removed the TB and TPS, checked the TPS and it functions properly. It clicks just as you open the throttle off the stop. I have tried a different AFM, a different ICV and the problem is identical.

 

This is related to a problem when starting. The revs jump up to 2.5k and then settle straight down to a fairly stable idle and the tacho seems slow to react but once on it seems fine, just that driving around slowly is a pain.

 

So can anyone suggest any possibles?? I really am totally out of ideas and as the title suggests I will pay money to whoever can fix or suggest the solution that resolves this issue I am that desperate.

 

Please please help!

 

Anyone in the Glocuester area who wants some beer enquire within!

[kyepan 291]

what is the number on the end of your ecu and is it two or three row.

 

as the cold start behaviour is the same on mine, and only started after i swapped over the.

 

The overrun also changed too, to have more overun, lots more than my standard ecu. This incidentally cured the hot stall problem.

 

do you have a fruity cam?

[Cameron 16]

Have you checked and cleaned the crank position sensor?

[Galifrey 1]

Can you reset an MI16 ecu or is a non learning one?

[Veero 1]

I forget the exact number but its a 3 row with knock but no lambda.

 

It's got a brand new crank sensor, along with the entire ignition system.

 

No idea if it's a learning one, how would you go about resetting it?

[Simes 248 2 Cars]

I forget the exact number but its a 3 row with knock but no lambda.

 

It's got a brand new crank sensor, along with the entire ignition system.

 

No idea if it's a learning one, how would you go about resetting it?

 

Switch it off I reckon.

 

I've a spare 3 row ECU if that's of any use, I reckon it's your TPS though.

[Veero 1]

Well thats what I thought, hence taking the TB off and testing the TPS. Pins 1-2 are closed circuit on closed throttle which becomes infinite resistance on throttle opening and pins 2-3 do the opposite, or the other way round, whichever it's supposed to be in the 2 row diagnostics manual.

 

Oh that's what I forgot to mention. With the TPS unplugged it won't run at all, I think the ICV goes wide open and the revs just keep rising so I just turned it back off.

 

PM me with how much you're after for the ECU, potentially interested,

 

Cheers

Veero

Edited December 23, 2009 by Veero

[KRISKARRERA 2 1 Cars]

Ahh you've still got this then. Me too. Worst part of mine is accelerating away in 1st with a cold engine and taking my foot off the gas as the revs drop towards idle and fuel is re-injected there's an almighty jerk like I've done the world's quickest emergency stop.

[Galifrey 1]

Mine is smooth as silk but it does hang on to some RPM when I lift off.

 

Am going to give the ICV a cleanup when I can work on the car and retain feeling in my fingers.

 

[M_R_205 5 1 Cars]

It could be worth getting the AFR checked, as when mine was running ritch it was very jerky at low speeds and low throttle.

[Veero 1]

Well the CO2 was way up on the MOT, so the guy tried adjusting with the idle mixture screw but it did nothing at all, so he popped the cover off the AFM and (didn't like it TBH) clicked something round a notch which brought it within tolerance. However it was jerky before and is still jerky after.

 

What's the best stuff for cleaning out the ICV?

 

Something I thought was wierd was that I don't have any breather lines going to the inlet tract as in the normal Mi16 setup, my oil filler cap just vents to by the jack. I have been meaning to sort this out and put in a catch tank and breather... Could that be causing any circulation issues? I don't see how as there's nothing that could even possibly connect the inlet to any un-metred air.

 

Also the throttle stop adjuster screw on the GTi6 TB is stuck solid so I have no way of fine tuning the throttle stop position. I remember reading the Haynes manual for the Mi16 TB and it saying you need to bring the butterfly a smidgen off fully closed, now I haven't got that at all so ALL the idle mixture air is going through the ICV so could the ICV be opening too far?

 

I'm really clutching at straws here

[DrSarty 90 1 Cars]

Hi Tris:

 

Happy Christmas yada yada.

 

I'm not a fan of oil vapour/crank case breathers feeding back into the inlet tract, BUT...when my original Mi16 engine was in the Citroen BX16, I seem to remember that if when you filled it with oil, you knocked off/didn't replace the breather hose between the oil filler neck and the inlet trunking (filter side of the TB) then the engine ran funny.

 

As you're clutching at straws, perhaps that's worth experimenting with.

 

The below pic shows the hose I mean.

 

 

I can tell this is doing your tits in, so I'm just trying to offer anything I can. When I come home (28th Jan) for a while, I'll be near Goliath, which I believe is near you too, so I can muck in and help out if it's still not sorted.

Edited December 27, 2009 by DrSarty

[Galifrey 1]

If you are cleaning the ICV I usually use Carb/Intake cleaner.

 

Get it nice and wet inside, turn the ignition on and off a few times to work the cleaner into the moving parts (don't start it)

 

Look to remove all the black/brown caking in the valve, a small toothbrush can help.

 

Make sure you have no airleaks and that where the breather system has been removed it is all blanked off correctly.

 

For the GTI6 Throttle body, try getting some WD40 on the screw and letting it soak in overnight, or over a few days. A high power soldering iron on the screw can heat it up and help loosen it.

[Veero 1]

Right I will have a go at releasing the TB butterfly stop and cleaning the ICV and see if that does owt.

 

I know the hose you mean Rich, since I have fitted the GTI6 inlet manifold I had to find a new link hose to the AFM and as a result don't have a take off for the filler pot lid now at all. Thats what I meant by it vents to air by the jack.

 

I really do need to get the crankcase ventilation sorted too though..

 

Final thought. I am running a GTi6 fuel pressure regulator with the Mi16 injectors and management. Is there any differences in the regulation of fuel between the two?

[Veero 1]

Ok so it turns out having the Mi16 ICV plumbed in the wrong way round makes a big difference. Gave it a clean out with some carb cleaner and activated it with a 9v battery across the pins a few times, turned it round and now it starts as it should. Revs peak at about 1500 before it settles down immediately.

 

I only had the ICV the wrong way round as it fitted slightly better having the Gti6 inlet manifold on there.

 

Ah well one mystery solved. It still is a bit slower than it should be coming off throttle but it's tons better. Ill be getting the injectors cleaned this week to so hopefully that will make things a little better too.

[24seven 104]

mine does exactly the same from cold. It'll start, bounce up to 2500 9if it's really cold it'll bounce between 1000/2500 more times) then slowly settle back down to 1000. For the first few minutes every time I tocht the throttle it tends to try and sit at 2000 and sometimes suddenly jumps and tries to settle back down instantly, jerking the car violently. My ICV is plumbed in the normal way round and definitely works fine (pretty much what kriskarrera described). Add to that the misfire I've got at part throttle (i've since found it's nothing to do with engine speed, as in neutral it'll misfire up to 4000rpm on light throttle, but in gear under load it'll accelerate perfectly cleanly without spluttering) and you've got a very poorly engine . Looking forward to the day I can afford some proper management for the bastard thing!!

[KRISKARRERA 2 1 Cars]

Mine does that too. In neutral if I rev it up to say 3000 rpm I can hear a pop coming from the exhaust.

[Veero 1]

Yeah mine still has a pop every now and again, it used to misfire all the way up to a few thousand revs in neutral too but that's much better now with a whole load of new ignition bits. I think mine is almost enjoyable now. Just wish it would go to idle instantly as you come off throttle...

[24seven 104]

Do you 2 have misfires at idle? mine forever idles on 3 cylinders, occasionally you hear it splutter on 2 cylinders, but it still maintains a solid 1000rpm despite this.

 

[edit] I'll see if I can record it to show you just how bad it is!

Edited January 18, 2010 by 24seven

[stuRALLYE 5]

im also having issues with mine as of today. it idles cleanly from cold but when accelerating it seems to lack power and hold back. its not sparking issue im sure, it feels like under fuelling. when the engine is up to temperature it behaves perfectly and pulls cleanly and strongly to 7,000rpm. anyone experienced this or can point me in a general direction of things to check?

its a 1.9 mi running mi 2 row management

cheers guys

[C_W 3 1 Cars]

Mines a 2-row ECU (ends 125), I did have one (140) that "held" the revs from 2000rpm down, but it annoyed me as it then didn't engine-brake below 2000rpm, felt like it was coasting when you lifted. I imagine there might be similar differecnes in 3-row ecus, probably BX vx 405??

 

I would put most misfires/hesitancy down to rotor arm and cap problems. You can't always visually check them either (replace the arm first as that does have some kind of resistor in it I think). This plagued my car for about 18months with an inconsistant misfire every now and then, a new rotor arm fixed it.

 

For the breathers, it depends which one it is, if it's the oil filler cap venting to air then thats alright I suppose, but not an inlet side breather.

[24seven 104]

Quick update on mine, the exhaust manifold/downpipe bolts/springs vibrated out on sunday night and as it must have been slowly coming apart for a while the gasket managed to chew itself. I replaced it today with an OEM kit and now the car idles a lot smoother (3 cylinders instead of 2), doesn't kangaroo anything like as much and is generally a lot better, though there are still some things to be sorted on it.