ECU reset/high idle

[TouringMatt]

Been doing some work on my Touring ( 325i ) which included me disconnecting the battery to do some welding.
I've replaced the TB to AFM hose, TB to rocker cover and TB to IVC hose, put a new filter in given everything a real good wash out with some carb cleaner.

Fired her up and my original problem has gone ( very poor pickup from idle ) but the engine now idles at 1200-1300 rpm ( was fine before! )

Got the meter out and the IVC is reading fine, tested the incoming voltage ( 3-pin ) and its 9v one side and only 4v the other, should be around 10v according to Mr Haynes, who also said this points to a possible ECU problem.
Because I had the battery disconnected ( around 2 hours ) does it need to 'learn' again or does it sound like the ECU is kaput?

Cheers
Matt

[Martinaston]

I'll try the obvious one first you never know. Accelerator cable to tight?
I thnk you check the IVC for resistance not voltage ? Not sure.
You may have dislodged the Throttle Position Sensor on the underside of the throttle body they are normally bolted into place and thread lock applied so you can see if it has been disturbed. If moved it sends a signal to the ECU as if the throttle is open. It's a pain to get to and the best way to tell is to remove the TB but that normally means a new gasket because there only paper.
If you cleaned it with carb cleaner that can make it run fast because that stuff is pretty combustable. Let it run for a while if you havn't already.

[Martinaston]

Also if the TPS has moved that could be the source of your original problem. They sometimes get filled with gunk running down from the throttle and give false readings even if it hasn't moved. check the resistanc with the meter is you slowly open and close the throttle and it should be a smooth increase/decrease. Any spikes and it's toast.

[Andy_magic]

My understanding of the ICV is that the valve itself should be checked for resistance between the centre contact and the 2 outer contacts, 1 at a time, and should read 20 ohms (+/-10%)

I'm pretty sure that the 2 outer contacts on the loom are supplies to drive the air bypass within the ICV to a set position, I think the earlier models did this in a different manner, which is why some ICV's buzz with the ignition on and others dont. The later type have both terminals driven at the same time, one more than the other to give a set amount of air flow through it. If that makes any sense.

The ECU will need to re-learn it's settings as you have disconnected the battery. I have read differing reports on the procedure for this, some say idle for minutes, others say drive for 45 minutes.

I would imagine that idling the car for 10 minutes won't set/learn the parameters for the whole rev/load range as it's just idling. I think 45 minutes may be a long time to program the ECU too. I usually start the car and drive for about 10 minutes, everything seems to settle down nicely after that much time.

The TPS is just that, a switch, it tells the ECU that the engine is idling or at WOT so with a meter accross the terminals is will show either continuity or not, going from 'idle mode' to partially open throttle will show a sharp drop off on the meter, likewise, hitting the WOT will show a sharp 'up' on the meter, indicating continuity.

I'm half way through writing a howto guide on the later motronic system as I've spent a heap of time reading up on the system as fitted to E30's and sorting out my once dog running 320i to the purring kitten it is now. I will be posting a link to it once its finished.

[TouringMatt]

Thanks for the reply Martin,

Yep, checked the cable and its tight, but not too tight and i forced the TB lever shut by hand to fully close the butterfly but it made no difference, thinking back tho i'm sure the idle was low the first time i fired up the engine and idled high only after i'd blipped the throttle a few times.

Yep, i check the Ohm reading on the IVC, voltage on the supply.

I left the TPS well alone when i had the TB off, and its been fitted to the car for about a week so any cleaner should have dried off?. I re-fitted the IVC and shot some more cleaner in before i did - should i have left that to dry for a while first?

Do i check the resistance in the same way i checked the IVC, engine off etc?

Cheers
Matt

[Andy_magic]

Carb cleaner evaporates very quickly so I wouldn't worry about that.

To check the TPS you need the engine off.

There are 3 contacts on the TPS, with it still attached to the TB put a probe on the centre contact and check for cont. on the left-most pin, this is the 'idle mode' pin, if you get cont., very slightly open the throttle, the cont. should drop off straight away.

The WOT is checked on the right-most pin and will actually happen at about 90/95% open throttle. The idle side of things is much more critical.

Once you have it sorted out go and get a CO check done, this is normally about a fiver. The spec for 6 cylinder E30's is 1% (+/-0.5%) although they tend to run best at the richer end 1.5%

The HC specs are 300PPM for a new car assuming your car is non cat.

[Martinaston]

Andy magic seems to have it covered I wouldn't worry about the cleaner, i normally use it to detect air leaks if you spray it around the hole the engine speeds up for a second or two. it comes in handy for all sorts (makes a good flame thrower too)

[TouringMatt]

Thanks Andy, thats great and i will try that tomorrow

Cheers
Matt

[TouringMatt]

Lol, i'll have to try that!, i know its damn cold when you get it on your fingers

Matt

[E30Adam]

Matt, when you remove power from the ECU for extended periods, it takes a while for the ECU to readjust and relearn the settings. I've had this a few times and found it was back to normal after a couple of days normal driving.

You'll find that it happens all of a sudden rather than gradually. When you stop at some lights it will suddenly idle correctly. Try to avoid completely disconnecting power in future because it can be a right pain in the butt!

[TouringMatt]

Update!

Gave the car a good run, ECU's now letting the car idle but today i have had horrendous cold start running problems.
Car fires up fine but straight away the idle drops to 500, splutters, almost dies and i have to hold the revs at about 2k for a few minutes.
Checked the TPS as advised about and i get no reading, i only get a reading on the other pins on WOT

Bugger!

Matt

[Andy_magic]

You'll probably find that you will chase various problems around but it's worth it in the end.

You will probably find that cleaning the TPS out with carb cleaner will sort it out. You need to remove it and give it a proper spraying with CC down the hole where the throttle spindle goes through.

Let us know how you get on

Cheers

[TouringMatt]

Yeah i was thinking, i cleaned a lot of crap out with carb cleaner but never flushed the TPS out, so quite possibly flushed gunk into it!

So TB off, good flush out and check resistance again?

Does i need to remove the TPS from the TB to do this best?

Cheers
Matt

[Andy_magic]

It's best to take the TPS off to clean it out, is it stress on your car??

It cant be as bad as a 6 pot one...

[TouringMatt]

Mine is a 6 pot - 325i

No real stress, just unbolting stuff - job for tomorrow

Cheers,
Matt

[Martinaston]

In the cold weather mine starts then stalls then runs rough untill warm and then continues to run a bit lumpy. I know this is due to 1 or 2 leaking injectors but i can't be bothered to find out which ones yet because it means draining the coolent to get the front nut off the manifold.

[Andy_magic]

Sorry mate, I must have been being mega-lazy, I didn't scroll up and read your first post...

Ther a bit of mare to get off but worth it in the end.

Martin, what engine is in your car??

[TouringMatt]

Something else i forgot to add but have been reminded about tonight, the car sometimes take a serious amount of cranking to get it to start.
When it was standing on the drive and i used to fire it up once a week to keep things moving, it fired on the turn of the key, seems to the more im using it the worse its getting

I marked the coolant level today and im going to park in exactly the same spot and re-check tomorrow.

Not sure ive got worsening seepage into the cylinders making it harder to start - sound possible?

Matt

[Martinaston]

The next time you have the car running when you turn it off don't use the key, instead pull fuse 11 for the fuel pump so the engine dies. Then let it stand for a day without any back pressure from the fuel rail, put the fuse back in and start it up. If it starts ok first time (run the starter motor for a bit longer than normal to give the fuel pressure time to build up) you can be pretty sure you have 1 or more duff injectors. Then its just a simple matter of finding out which ones and replacing them.


at Ԛ£40 each



An indication of this is excess water from the exhaust when you first start up. Thats unburnt petrol that sits in there and rots the exhaust if not fixed or ruins your catalyst if you have one.



Andy 89 320

[hogweed]

Mine had the same problems ages ago but it was just the loom-to-TPS connector full of crud, no need to open or disturb the TPS at all to test that one... if the TPS mistakenly tells the ECU you're off idle when you're not, the idle will rise to well over 1000rpm.

And if you unplug the ECU, it'll idle like shite for hours of driving till it re-learns.

Hope that helps...

[TouringMatt]

Thanks for the replys

Didnt get chance to check owt tonight, had to sort out my 'rents PC

I think the connector is crud free, as i actually got the probes onto the TPS pins and it failed the check, i'll give it all a clean out anyways

What i did notice was this though, left my 'rents house ( car has been standing for about 2 hours ) and drove 3-4 miles to pick my g/f up from the station, left the car idleing for about 10~12mins, then drove about another 3 to her flat, all gentle stuff, sub 3k revs etc then left the car idleing for another 2-3mins whilst i was talking and noticed a slowly increasing amount of condensation drifting past the tailgate window

I'm thinking this is not good!!

Matt

[TouringMatt]

Yay!! Another update

Car is losing water, not 100% sure its the head but thats a problem for another day.

Took the TPS off today, cleaned it out and re-tested. Kaput, no reading.
Went searching on the net for prices ( not cheap!! )and my Dad got involved. Liking an electrical challange he said since it was scrap he was gonna take it apart. 15mins of stanley knife cutting and he had it open - and found the problem!
One of the connectors to the microswitch had bent and come unstuck, bent back and re-soldered and it worked

Bit of superglue and used the soldering iron the melt the cover back together, re-assembled and working a treat

Fantastic

Matt

[Andy_magic]

Sorry to hear about the water issue but glad you sorted the tps out. I love a bit of ingenuity.

What prices were you quoted out of interest.

Next time your down the scrappy you can probably get one - as long as you've plenty of pocket space - lol

[TouringMatt]

Euro Car Parts were about Ԛ£37, GSF Ԛ£46 IIRC, both plus VAT

Quite pricey when you consider all it is!!

Just think of all those TPS's thrown away that my Dad could have repaired.......

Matt

[Andy_magic]

Not tooo hideous then, I'll be keeping my spare for now just in case.

[hogweed]

What you want to do in your spare time is go round the breakers (or ask people here if they have any for sale) and build up spare stock of:

TPS
AFM
ECU
ICV
Throttle body

That's what I've done... then it is *SO* easy to test for problems by substitution, and you're not stuck between having no car and paying a small fortune for a new part (ECU was about Ԛ£450 at the last count, but pay no more than Ԛ£50 for a used one) next time your Beemer goes all huffy and refuses to play.

You'd probably only pay a fiver for a TPS, or even the whole throttle body complete with one!

[Andy_magic]

I bought my first E30 about 3-4 months ago then picked up a touring with 330k on it spares, transfered bits over, got the first one running sweet as a nut, then stumbled on a bad running 320iSE in much better shape than the first one for a song.

I used lot's of parts from the first one to sort the current one out, I can vouch for having the parts!

I'm going to have to re-stock on some of the bits though as it's getting a 2.7 in it soon.