Annoying Idle Leading To Stalling

[Simes 248 2 Cars]

I've been experiencing an annoying and frustrating idle problem since I moved over to my new set up. The problem is I'm getting fluctuating revs on idle that escalate from + - 100rpm from idle building all the way to + - 500 rpm which in turn leads the car to stall.

It only seems to do this when the engine is really hot and is evident after being in a traffic queue. Although yesterday it was particular warm I was also having similar issues back in Feb when it was cold.

I don't drive the car that often so it's not urgent to sort however it can be frustrating and riding the clutch, braking with the handbrake whilst feathering the throttle can be annoying.

 

My set up is

 

Mi16

Wasted spark

Mi16 ICAV

Emerald

GTI-6 inlet manifold

Couple of 262 cams.

 

I keep meaning to plug the laptop into the emerald and monitor it whilst driving but I never seem to get around to that. I'm wondering whether one of the sensors is failing or similar. Dave Walker did mention something about cams / plenum being the problem but it idles beautifully most of the time when up to temperature (cooling fan kicking in) and then on other occasions is a complete and utter nightmare.

EDIT: I've already swapped the ICAV

Edited July 3, 2010 by Simes

[GLPoomobile 958]

Air leak maybe? I know that when this problem has been attributed to worn throttle bodies on Mi16s (and I know you are using the GTI6 setup, but I guess it's still a possibility).

 

Apart from that I'd assume it must be a sesnor failure. But which? My Mi did the same when the AFM shat itself. Coming to a stop and coming off the throttle the revs would drop down to about 800rpm, causing the Motronic to over compensate to avoid stalling and it would bounce back up to about 1500rpm, then drop back down again, and this would go on for a few seconds until it inevitably stalled.

 

Sorry, not much help

[Simes 248 2 Cars]

Anyone else?

 

I could get the car to stall whilst driving yesterday at 50mph+!

It's really annoying more so when you're trying to pull out and the revs die!

[matyasg 0]

I've been experiencing an annoying and frustrating idle problem since I moved over to my new set up. The problem is I'm getting fluctuating revs on idle that escalate from + - 100rpm from idle building all the way to + - 500 rpm which in turn leads the car to stall.

It only seems to do this when the engine is really hot and is evident after being in a traffic queue. Although yesterday it was particular warm I was also having similar issues back in Feb when it was cold.

I had exactly the same problem with my mi16 with MS1. I didn't solve it because of a project change, but I was told later that it's more than likely that the "injector opening time" value was not set properly. Maybe worth a try if it can be set on Emerald too.

[Simes 248 2 Cars]

grrr still doing it, but now no trend as to when and how.

Just leafing through Dave Walkers engine management book to understand about sorting stalling etc.....I expect money will fix it!

[Richy_cti 0]

what the car idleing at? my 1.6 was idleing low just ajusted the idle control vales it idels just over 1000rpm and never staled since

[Simes 248 2 Cars]

what the car idleing at? my 1.6 was idleing low just ajusted the idle control vales it idels just over 1000rpm and never staled since

 

Thanks for that but I'm running an Emerald managment system - not the standard Bosch Jetronic or Motronic.

[Simes 248 2 Cars]

Well still not had the time to carry out a great investigation, looking through the Emerald book it seems it is based on the

 

Fuel

Ignition

and fuel vapourising before entering the cylinder, then it over compensates etc etc.

 

I've been thinking of tinkering with one of the maps to try andf cure it. However when warm and being irritable unplugging the ICV seems to fix it!

[matyasg 0]

Well still not had the time to carry out a great investigation, looking through the Emerald book it seems it is based on the

 

Fuel

Ignition

and fuel vapourising before entering the cylinder, then it over compensates etc etc.

 

I've been thinking of tinkering with one of the maps to try andf cure it. However when warm and being irritable unplugging the ICV seems to fix it!

Have you solved this? I'm curious what will be solution.

[Simes 248 2 Cars]

Have you solved this? I'm curious what will be solution.

 

Not yet - but have some suspicians.

I am curious too, but also a little bit lazy hoping it will go away.

[matyasg 0]

Not yet - but have some suspicians.

I am curious too, but also a little bit lazy hoping it will go away.

Be optimistic Please share us the solution if you find it.

[luggy 13]

Shot in the dark

Just had a look at your re-shell pics obviously no TPS with the GTi6 manifold but I notice the MAP sensor isnt connected up. Doesnt the ecu need some signal from the intake side on load to change from idle to WOT? or am I barking up the wrong tree?.

[sideways danny 0]

sounds to me like one of 2 scenarios.

 

1. TPS problem, either not setup correctly in the software, or it's moved/come loose/become faulty. This would mean the ECU doesn't know when to engage idle conditions

 

2. Idle motor at fault. Either a faulty motor (even good used ones are pretty crap) or the control setup telling it what to do is wrong.

 

You will not be able to do a thing without plugging in the laptop, and from doing so you should be able to tell if idle condition is being switched on when you would expect

[sideways danny 0]

Shot in the dark

Just had a look at your re-shell pics obviously no TPS with the GTi6 manifold but I notice the MAP sensor isnt connected up. Doesnt the ecu need some signal from the intake side on load to change from idle to WOT? or am I barking up the wrong tree?.

 

I'd imagine he's using TPS for load. MAP for load on N/A is pretty unusual except for OEMs. Some people will use a 1bar MAP sensor for barometric compensation, but rarely for primary load sensing

[Simes 248 2 Cars]

Thought I'd get back onto this problem.

Welll I solved the crazy wild idle by unplugging the ICV but leaving it physically in place and disabling in the ECU.

 

I think now that I have a new problem as the revs seem to stick at 2000rpm every but a quick blip of the throttle stops that, this has been getting progressively worse.

 

I though I'd run through some tests again (obviously months apart!)

 

When revs stick at 2k - plug in ICV and they drop

Unplug ICV again.

When revs stick at 2k - throttle is physically back on its stop indicating that the butterfly is closed.

 

I'm wondering whether the TPS is at fault? Problem is its a GTI-6 TB and the TPS is rather awkwardly placed!! I'll probably take another month to look at that!

 

Anyway - do the GTI-6 TPS fail at all, is there a history of this? - I've had a look on GTI-6.com but no real joy apart from they are expensive!

 

Anybody else have any ideas???

[Tom Fenton 1,525]

PLug a laptop in and you will see straight away if the TPS is giving a true reading, and also the other sensors are giving believeable readings.

 

This for me is the beauty of mappable ECU- you can plug in and see exactly what is going on if the engine starts running funny.

[petert 550]

I'd imagine he's using TPS for load. MAP for load on N/A is pretty unusual except for OEMs. Some people will use a 1bar MAP sensor for barometric compensation, but rarely for primary load sensing

 

I disagree entirely. Where did you hear/read that? MAP sensor is a far better solution for a N/A engine with a plenum type manifold. It will give a far quicker and more accurate reading of engine load than TPS. I only use TPS for throttle body applications. And even then, I put the fuel on TPS and the ignition on MAP if possible. A properly mapped N/A plenum engine doesn't even need a TPS, other than to detect throttle transients.

 

You usually can't use the GTi6 MAP sensor however, as they work backwards electrically for most aftermarket ECU's.

 

I would remove/disconnect the ICV and make sure the engine idles correctly on just the throttle body when at operating temp. Falling idle is usually caused by too lean a mixture, which could be incorrect mapping or an air leak. You need to completely disconnect the ICV to make sure no air is passing over the valve. Once you've got it sorted without the ICV then reconnect and try again. What values are you using for the Mi16 ICV? These can be a real bugger to get working correctly.

Edited May 5, 2011 by petert

[unariciflocos 49 1 Cars]

From a control point of view it would point to bad mapping. Oscillating by +-100 then ramping up to +-500 is a sing of an overcompensated control loop, with a proportional gain higher than it needs to be.

 

You really need to go intro the ECU and see what's happening. As Tom said, that's the beauty of aftermarket ECUs.

[Simes 248 2 Cars]

PLug a laptop in and you will see straight away if the TPS is giving a true reading, and also the other sensors are giving believeable readings.

 

This for me is the beauty of mappable ECU- you can plug in and see exactly what is going on if the engine starts running funny.

 

 

Yep - done this and the values are fine although I haven't had a chance when the throttle is 'stuck'

 

 

 

I would remove/disconnect the ICV and make sure the engine idles correctly on just the throttle body when at operating temp. Falling idle is usually caused by too lean a mixture, which could be incorrect mapping or an air leak. You need to completely disconnect the ICV to make sure no air is passing over the valve. Once you've got it sorted without the ICV then reconnect and try again. What values are you using for the Mi16 ICV? These can be a real bugger to get working correctly.

 

Thanks, ICV is unplugged and it idles beautifully - the 'crazy' idle seems to exhibit itself once the temp goes over 66deg C, DW suggested the weak mixture problem too.

it's the sticking throttle though which is my current gripe

[Toddy 7]

Sticking/Holding Revs would be explained by an air leak on the inlet side, plugging the ICV in would reduce the amount of air it allows in therefore bringing the revs down, it would also explain the uneven idle as the ICV would try to compensate for the unmetered air.

 

I would replace the inlet manifold gasket, throttle body gasket & ICV 'O' ring. When you have the inlet manifold off check the resonator for any cracks, iirc you have a GTI6 inlet.

 

The air leak is probably too small to locate by spraying carb cleaner etc.

 

Cheers

[sideways danny 0]

I disagree entirely. Where did you hear/read that? MAP sensor is a far better solution for a N/A engine with a plenum type manifold. It will give a far quicker and more accurate reading of engine load than TPS. I only use TPS for throttle body applications. And even then, I put the fuel on TPS and the ignition on MAP if possible. A properly mapped N/A plenum engine doesn't even need a TPS, other than to detect throttle transients.

read what i said. UNUSUAL. I made no mention of any technical benefit either way. It's far more common for TPS to be used with an aftermarket ECU as primary load. And I didn't read or hear it anywhere, I worked for OMEX, and setup dozens of cars like this, including my own clio

 

You usually can't use the GTi6 MAP sensor however, as they work backwards electrically for most aftermarket ECU's.

 

 

Canems ECU can simply tick a box and you can reverse the signal

[Simes 248 2 Cars]

Sticking/Holding Revs would be explained by an air leak on the inlet side, plugging the ICV in would reduce the amount of air it allows in therefore bringing the revs down, it would also explain the uneven idle as the ICV would try to compensate for the unmetered air.

 

I would replace the inlet manifold gasket, throttle body gasket & ICV 'O' ring. When you have the inlet manifold off check the resonator for any cracks, iirc you have a GTI6 inlet.

 

The air leak is probably too small to locate by spraying carb cleaner etc.

 

Cheers

 

 

Thanks for your help - I'll check those things out.

Just to mention again though - FRom cold until around 66deg, with the ICV plugged in it idles really well. It's just once it starts to really hunt it becomes truely awful.

[feb 47]

Could it be a bad coolant temperature sensor? It wouldn't explain the hunting though.

 

Do you have trouble starting the car when warm?

Edited May 6, 2011 by feb

[petert 550]

I worked for OMEX, and setup dozens of cars like this, including my own clio

 

That doesn't make it right. Anyway, it's probably more of a local thing, as UK has a lot more 4cyl cars, where vacuum is weak on performance cars. Here, we have more turbos, 6cyl and V8's where vacuum signal is strong. I've only been a Haltech dealer since '93 so please be gentle. I also used the word unusual. In latest Haltech's the inputs are fully programmable, so anything is readable. Sorry to get off track.