Mi16 Running Problem

[gti_al 1]

I'm not sure what is going on, but it is odd

 

Yesterday i went to take off from some traffic lights, and the car didn't really want to go. It doesn't misfire as such, but just has absolutely no power if i go to accelerate at all quickly. If i'm very gentle it is fine, but on any bigger throttle openings it just won't do anything... but if i lift a bit it will start accelerating again.

 

This all seems very strange, but i swapped the tps thinking it may have something to do with it. I don't think it did, as it is still the same. I was thinking it might be ignition amp or coil related, but as it is idling perfectly and fine when being driven carefully it is a bit hard to test.

 

Does this sound familiar to anyone?

[Tom Fenton 1,542]

Sounds like a possible air flow meter problem to me.

[gti_al 1]

I think you are right tom. I disconnected it, and nothing has changed.

 

When they get this bad is it worth trying to retrack the afm, or should i just get a replacement? I've always said when it dies i will get an aftermarket ecu, but now isn't a great time...

[Tom Fenton 1,542]

Before you condemn the air flow meter itself bell out the wiring back to the ECU plug. But if this is OK then you'll need to do soemthing with the AFM. Personally I've never had much luck retracking them, but up to you.

[AndyJ 1]

Could be the coolant temp sensor going out the window, causing it to go very rich when you floor it and bogging down?

 

Mine doesnt even run wuth the AFM unplugged so you must have a different ecu to me

[gti_al 1]

Before you condemn the air flow meter itself bell out the wiring back to the ECU plug. But if this is OK then you'll need to do soemthing with the AFM. Personally I've never had much luck retracking them, but up to you.

 

That was the first thing i did when it started playing up. I figured it would be that, but it all looks fine. When i converted it i checked everything, and wrapped it, so it should be ok.

 

The car has always idled pretty roughly too, so i've wondered whether the afm is any good. I didn't hold out much hope for retracking it anyway, and it has done 350 000kms, so i'll try and find a replacement.

 

I don't know why it runs without the afm connected... my old 405 did too. It is a bit rough, but if you are gentle with it there are no probs. I suspect it probably isn't very good for it if the mixtures are way out, but it does work. It could be the coolant sensor i guess, but i suspect it would be harder to start, or not idle when hot. I might just try another afm, and if that doesn't work investigate further, and perhaps get more scientific.

[kyepan 291]

Probably wouldn't bother retracking it just yet, 10 mins with the volt meter and you'll know for sure if it's the AFM.

 

Try back probing the afm with the ignition on, take the air filter off and depress the paddle with something long and check the resistance is within tolerance though out the range.

 

You can also take it off the car to do this.

 

Then back probe the corresponding pins on the ecu (depending on where your's is this might involve sitting upside down in the foot well) whilst an assistant does the same prodding on the afm.

 

check the sticky on the CAPS program at the top of this forum for more detailed information on which ecu pins to probe and the resistances.

What's it like at the top end because the air flow meter maxes out at 4-5k and if it's still behaving like this at the top end, it might be worth looking elsewhere. For example, it could also be one of the ignition components breaking down under load.

 

hope this helps.

 

J

[gti_al 1]

Thanks... i tried the other afm anyway, and it is idling much better. But still not pulling

 

I thought i should check out the ignition side of things, despite this not feeling like any other mi16 ignition problem i have had. The dizzy cap and rotor were looking pretty crap, and after a clean up it is behaving better, but still not right. I think i will replace them, and probably the leads this arvo, as they are pretty average looking, and looking like the cause of a weak spark.

 

Thanks for that info though. I will investigate retracking my afm, even if just to have a spare. It is idling very nicely now which i am happy with

[pug309twin40s 1]

does sound like AFM. i've got a collection of 4 16v AFM's!! and 1 of them when fitted the car just bogs down and doesnt accelerate with more then light throttle.

[gti_al 1]

I haven't got my multimeter with me this week, so i can't check the afm and wiring which is annoying. The 205 shaped ornament is starting to pose problems though, so i'm still thinking about this.

 

Is it true that above 5000rpm the air flow meter is out of the equation? I'm just wondering, because somebody has mentioned that, and it would rule out the afm here.

 

Also, should i add the ignition amp to my list of things to swap? I'm not entirely sure if it could cause spark problems that would manifest in this behaviour.

[gti_al 1]

Hey guys. Sorry to keep bumping this up, but i have improved things significantly. I changed the afm, plugs, coil lead and rewired lots of things. Now it is pulling really hard and cleanly, but at low revs it still has a stutter. If it is idling, and i give it a bootful the revs will die, but from about 2500rpm it is behaving perfectly.

 

It seems odd that it keeps improving, but won't go away completely. I noticed that the ignition amp didn't have any thermal paste between it and the metal plate - that isn't right, is it? Could it create problems like this?

[kyepan 291]

Hey guys. Sorry to keep bumping this up, but i have improved things significantly. I changed the afm, plugs, coil lead and rewired lots of things. Now it is pulling really hard and cleanly, but at low revs it still has a stutter. If it is idling, and i give it a bootful the revs will die, but from about 2500rpm it is behaving perfectly.

 

It seems odd that it keeps improving, but won't go away completely. I noticed that the ignition amp didn't have any thermal paste between it and the metal plate - that isn't right, is it? Could it create problems like this?

it sounds like an air leak, take the air filter off, manually move the afm flap gently, if the running stablises, it's definitly a leak..

 

although that being said, mine running an 061 ecu used to stall when you blipped it, and worse in the wet, but didn't on a different chip in the same ecu...

[gti_al 1]

it sounds like an air leak, take the air filter off, manually move the afm flap gently, if the running stablises, it's definitly a leak..

 

although that being said, mine running an 061 ecu used to stall when you blipped it, and worse in the wet, but didn't on a different chip in the same ecu...

 

I have been thinking the same, as i've replaced everything else i could imagine is responsible

 

It is odd that it is idling normally though, as i would imagine an air leak would affect it somehow. Maybe i should try another ecu? It is starting to get really annoying. Very little happens when i play with the afm flap while it is idling anyway - does yours respond dramatically if you do that?

[kyepan 291]

I have been thinking the same, as i've replaced everything else i could imagine is responsible

 

It is odd that it is idling normally though, as i would imagine an air leak would affect it somehow. Maybe i should try another ecu? It is starting to get really annoying. Very little happens when i play with the afm flap while it is idling anyway - does yours respond dramatically if you do that?

 

Difficult to answer without being too subjective, i would say yes. if you slowly open the flap it should gradually run rough until it barely runs and dies when the flap is wide open and the mixture too rich. if it's not...

 

 

also if the idle control is masking the problem that may also be a factor, MI management controls idle only when the throttle switch is closed. and there is an adjustment screw... i think it's on the afm, once again caps can tell you what the standard readings should be, you might find that somone has wound it right the way one way or the other.

 

What i'm saying is if the idle mixture has been wound right up to compensate for the leak (if there is a leak) then as soon as the throttle is opened and the switch opened, it will start metering air in the open loop with the afm, at this point it will be way out and run like poo.

 

what were your readings from the afm resistance test?

[gti_al 1]

It seems like an afm problem, because moving the flap does absolutely nothing. I tried another afm though, and it was the same

 

I installed the caps program too, and it won't open. It says something about font and closes... i have the afm off, and a multimeter next to it... not sure how this stuff works though. I haven't really used the multimeter for anything other than checking batteries and whether wires have power or not

[gti_al 1]

Fixed! It was the ecu. It wasn't recognising anything from the afm, and i think it was running really lean

 

Anyway, thanks heaps for the help. It is always greatly appreciated when i'm tearing my hair out. It is going so hard too, which must be down to all the bits i have changed. I love this car!

[kyepan 291]

glad you got it running, well done!