E30 AFM Screw messed with, Faulty coolant sensor ?

[Shiz]

Ok guys. I've had my first e30 for 3 months now and I am loving every minute ive changed quite a lot of things now thanks to the help of use guys. However one thing I have tip-toed around is the hesistating idle, coughing and the smell of fuel when cold. I then discovered that the screw in the afm did infact do something, I thought with my bong missing that someone has just wedged a screw in there. It has increased in revs now and running far better due to the pot luck. I also red that if the bong is missing it more than likely has been tampered with. So now it is idling at 1500 rpm, which is relatively high, considering it was coughin at 700rpm. I now am in a dilemma, she is very sore on juice, roughly 80 miles to 20pound. 15ltres or whatever. I dunno what e30s relatively do, there is 180,000 and she is a 318. Just wondering what would folk recommend to make it run better, idle better and be a tad easier on fuel.. I am looking to change/ test the coolant temp sensor, however with it being an m40 engine its right below/underneath the intake manifold. Is it hard to remove the top intake manifold. Again guys, thanks for the help/

[Grrrmachine]

If you think someone's been tampering with the AFM then take it to a test centre and have the exhaust gas analysed - it's the only way to be sure. Other than that, do all the standard checks for air leaks in the intake system, as outlined in the Wiki on the "Intake" page.

For the rest, 25mpg isn't too bad for a 318, depending on how it's driven. A proper service might help.

[Shiz]

the car just went through the mot, and surely the exhaust gas was analysed then. She has recently been serviced, new plugs, oil, air and fuel filters, new oil. new gearbox and diff oil and replaced the rubber hose from the afm to the idle control. Its the kangoroo petrol at low revs and the hesistating idle is confusing me ?.. the car runs better when it is idling higher. When I turned the afm screw clockwise it made the car idle higher. When I turned it anti cw it never started at all and alls you could smell was petrol. Ive herd before that people adjust there afm screw to compensate for a faulty/failing coolant temp?

[Brianmoooore]

The problem is that you are now in a Catch 22 situation. The AFM can only be adjusted to its correct setting when everything else is spot on, but with the setting having been messed with, correcting faults will quite likely make the engine work worse.
You need to get the injectors rebuilt for a start (see our traders' section), and ensure that there are no air leaks whatsoever on the induction side of the engine.
You test the coolant temp. sensor at its pins on the engine ECU, not at the sensor itself. If you decide it needs changing, the top half of the inlet manifold is very easy to remove. BMW designed it this way to provide access to the sensors and all the pipes under there.

[Shiz]

thanks brian. the car itself seems to be running and going 100% bar this. its like you said i am scared to work at anything cause it could end up 10times worse. would you recommend opening up the afm and working at that. or try and turn the screw back to a seyting that is not running rich. i pressume cloxkwise is richer and anti cw is leaner?. when you say injectors brian your freaking me out. is it hard to do and would that be causing the idling problem. so test the resistance from the ecu pins.

[Brianmoooore]

Where you have a molested AFM and unknown other things adjusted, plus possible faults, then ideally you want to borrow a known working AFM with its seal intact. That then eliminates this from the equation, allowing you to concentrate on the other things.
Injector rebuilding is simple enough - you simply remove them, send them to Injectortune with £46, and then refit them when they come back. There's no feedback loop controlling the mixture on the majority of E30s, so their performance being within spec. is fundamental to the engine running properly.

[Shiz]

i will try and borrow an afm and go from there, you have reassured me with the injectors. However I don't want to start touching something that is working quite well it could end up worse. I was just wondering what mpg they average. Suppose it doesn't help I had a diesel golf before which done 60 odd mpg. but then it was boring as fook. thanks again brian, your a legend.

[broadie]

I'd start with setting up the throttel stop to the throttle position switich, check air hoses for leaks and try to get the co set by a garage.
Then is it running better hot or cold?

[Brianmoooore]

i will try and borrow an afm and go from there, you have reassured me with the injectors. However I don't want to start touching something that is working quite well it could end up worse. I was just wondering what mpg they average. Suppose it doesn't help I had a diesel golf before which done 60 odd mpg. but then it was boring as fook. thanks again brian, your a legend.

If the injectors have seen more than 50,000 miles, then they are due for a rebuild. They will be flowing less fuel when they should be, still flowing fuel when they shouldn't be, their spray patterns will be poor, and their flow rates will be imbalanced. If the injectors aren't flowing exactly what the software expects them to be, then the CO adjustment cannot be set to where it should be.

[broadie]

How did you get it to idle at 1500 rpm?

[Shiz]

so brian would you recommend sending them to Injectortune for a rebuild ? where are they based and roughly whats the lead time ?.. Due to it being my daily I need it everyday for work. Broadie, I don't really want to start messing with the throttle because she seems to be going alright. How I got it to idle at 1500rpm was simply by turning the afm screw clockwise, which I presumed ment less air, air that can be controlled and richened the flow. Before it would cough around for a wile, then sit at 900rpm.

[suedenim]

Buy a good second hand set of injectors and send them to injectortune, sell yours on when the refurbed ones come back.

[Brianmoooore]

DO NOT TOUCH THE THROTTLE STOP. This is another factory setting that never needs changing.
Of course, the kind of muppet that has messed with your AFM screw is also the type that might mess with the throttle as well, so you may be too late.
If the screw looks like it's never been touched, then leave it alone. The TPS does suffer from slight mechanical wear, and might just need a minor adjustment to match the the stop.
I think Injectortune gets the rebuilt injectors back to you in about a week, from what I've read on here.
Plenty of second hand injectors around. 316i, 318i and 325i ones are all the same.

[Shiz]

surely a rebuild is just a matter of changing the filters and seals ? and giving them a good clean. Obvs sending to a specialist would more than likely involve some kind of sonic cleaning, in relation to a can of carb cleaner. I would rather get the afm sorted first, there are guides online in relation to the teeth and tweeking the inside, in comparising to a screw...

[suedenim]

Pm'd

[Grrrmachine]

I have a feeling this is going to go round in circles...

Shiz, listen to Brian. The E30 engine is not a clever one; it expects things to be set up right to work properly, but it has no clue when things are set up right or not. The last thing that gets adjusted at the factory is the AFM screw, because IT CAN ONLY BE SET WHEN EVERYTHING ELSE WORKS.

We have no clue what state your injectors are in, whether you've got air leaks or not, or whether your blue temp sensor is doing what it should. Without that, fiddling with the AFM is utterly meaningless, and you'll hear that from people on this forum as well as the blokes at the BMW dealership. The difference is the dealers will charge you a few hundred quid for the info we're giving you for free.

Your car is over two decades old. A can of carb cleaner will do next to f-all to the injectors. Injectortune will put them back to original condition for half the price of one brand-new injector. Get it done.

There is nothing else we can tell you other than what's been said in this post already, and in the archives a thousand times over.

[Shiz]

Yeah grrrmachine, I hear what Brian is saying. I know what needs to be done, but its knowing where to start, first step is to get my hands on another known or well functional car afm. And go from there, if it fixes the problem, then that's all being well. However if it doesn't then looking at the temp sensor and injectors would be an option. I have replaced the intake pipe as it was cracked... I am sure the injectors need done, but I would plan on going at that some other stage. The car was running 100% only the hesistation has got worse in the cold morning. Being told I'd start with setting up the throttel stop to the throttle position switich'' is the reason why I am asking for 2nd opinions. I presume the AFM just unclips?

[Grrrmachine]

Intake pipe is only one of about a dozen places for air leaks to occur. There are also the hose inlets on the intake manifold for the ICV and brake servo, the servo connections, the rubber hose to the rocker cover and the rubber bung underneath the throttle body.

The AFM usually just unclips, but on big engines it has retaining bolts to a bracket on the inner wing - not sure how it's held on for the smaller engines.

[broadie]

I'm no expert but the fact you can achieve 1500 rpm on the mixture screw makes me think you have an air leak or the throttel stop has already been messed around with.

[jimbom30cab]

yer and i'd fit a known working ICV and see if that makes any difference also

[Shiz]

ok guys. I have tested another mates untouched afm and plugged it into mines, and it runs far better, no coughing or nothing. Aye then put my old one back in and tryed it without it plugged in. It ran awful, while bad smell of petrol and coughin around 500rpm. I then revved her for a while and she came back up to 900rpm and sat there. What would have caused this rougherrr idle, to much fluid went to the plugs ? worth cleaning the plugs guys ?

[Shiz]

would a afm m42 work on a m40 with no adjustment screw?

[Brianmoooore]

M42 AFM is the same as the M40B18 AFM, but the 1.6 uses a different one.
All are available in versions with or without a CO adjustment. The ones without can only be used on cars with lambda sensors, unless you add a pot. elsewhere and connect it to the wiring.

[Shiz]

how do you know if it has a lamda sensor? did you get my pm brian?

[Shiz]

First thing, i would like to say thanks very much for the much needed help people have provided throughout my threads. The problem I was having. the afm had been tampered with previously, the screw on the afm had been tweeked as well as the throttle screw. So in the mornings she would cough a lot. I tried my friends working m40 afm and it worked perfectly. I then contacted a zoner on here who said he had one however it didnt have a screw on it. I had read that m42 318is came without one. however he assured me it worked great on his 318i so I went ahead with it. So tonight it arrived I gave it a clean and swapped them over everything seem to connect up correctly except for not having an adjustment screw. on start up it revved to 2k rpm immediately and gradually came down to just about 1000rpm after I adjusted the throttle screw that has also been altered it to compensate for the dodgey afm. After the throttle screw was adjusted the car sounds to be running different. not coughin but like a boppin noise, i noticed the exhaust fumes where blowin like random circles. she does seem down in power a bit and is concerning that she is running even worse. Am I missing something ?.. I cant understand it should work 100% as I already tested a fully working afm?

[Brianmoooore]

I'm afraid I rarely look at my PM inbox. There's probably around fifty unanswered ones there, and it would take me about a week to work through them.
There is a four pin round electrical socket clipped to the underside of the front battery tray. E30s with a lambda sensor will have a plug fitted into this, connected to a wire that disappears underneath the car under the clutch fluid reservoir. E30s without a lambda sensor (the majority of them) will just have a blank cap on the socket.
If you use a late AFM, without the adjuster, on a car without a lambda sensor, there will be no signal on the CO input of the ECU, neither a varying signal from a lambda sensor or a default value from the adjustment pot, so it won't run as it should.

[Shiz]

thanks brian. yeah man i have put the old afm back in and she runs a hell a lot better i pressume minea doesn have a lamda sensor as the car ran like a bag of dung with the 'new to be afm. i cleaned he throttl body out and the flap was full of gunk and oil. she seems to be running better now. how do.you test a throttle sensor