Idle & Running Issues - 1988 325i Auto

[jimjambeal]

Hi all,

Apologies if this doesn't belong within this part of the forums, I'm new and wasn't 100% sure of the best place.

I'm in desperate need of advice regarding a running issue on my 1988 325i auto and really hope someone can help.

Apologies for the lengthy post, but I want to give you all the facts.

My car always ran perfectly up to about 4 months ago. Started first time, every time. Idled between 700 and 800 rpm depending on how cold it was, offered a smooth, but powerful ride and was also great on fuel.

I then noticed it would struggle to give me top gear. About town I would have to be at 40mph + to be able to get that final change and even then it seemed to be running rich. On the motorway I can still be doing up to 2500rpm at 70mph - def not right compared to how it used to be.

Things got worse when it wouldn't start one day about 2 months and it took 5 or 6 attempts to get it running - it has done this on the odd occasions since.

Since then it has been idling high - at about 900 -1000rpm, runs rich when driving and runs lumpy on start up.

Previously the car would idle smoothly and then when placed in drive and the break released it would move slowly forward before any throttle is applied - as it should. Since the above issues have appeared it idles high as mentioned above, but when you release the break it begins moving forward and once it's gained a little momentum, the revs will rise to 1200 - 1400rpm and it will pick up speed - still without any throttle being applied.

It has had a full/major service (plugs, all filters, fluids etc) and at the same time had a new Rotor Arm and Distributor Cap. In an effort to fix the above it has also been checked for air leaks, had a new Fuel Regulator, Idle Control Valve and the MAF has been checked and is all working correctly.

I'm certainly no mechanic and the garage are starting to scratch their heads.

Any help with this very frustrating issue would be much appreciated.

Many thanks


Jamie

[Grrrmachine]

Sounds like a classic case of blue temp sensor to me:

http://www.e30zone.net/e30zonewiki/inde ... emp_Sensor

[jimjambeal]

Hi,

Thank you for your prompt reply.

This was another area the garage suggested when I collected the car today.

They removed the blue sensor and it made no difference to the running of the car which led then to believe it may be faulty.

They are going to advise on a price for a replacement tomorrow.

This sounds promising though.

Many thanks


Jamie

[votivequagmire]

Well as I read through I first thought air leak , but then when you said it had been checked for this then , yeah I agree with the above.

[Grrrmachine]

Or it could be the wiring rather than the sensor itself. Which is why the wiki page outlines a clear TESTING procedure, rather than just replacing the unit.

[Brianmoooore]

Measure the temp. sensor's resistance at the ECU plug, with the engine stone cold, and then at running temperature.

[jimjambeal]

Thanks for all your advice and suggestions. I'll put these to the garage tomorrow and hopefully they can get it sorted.

[Brianmoooore]

I hope your faith in your 'garage' isn't misplaced. It's not very confidence inspiring if a 'mechanic' can't sort a simple engine like this in a very short time.
I don't know your circumstances, but my usual advice in cases like this is roll up your sleeves and get your hands dirty.

[Mitchen]

Just out of curiosity, which one on this diagram is the blue and which one is the green sensor?

Is it between 13 & 11?

http://www.realoem.com/bmw/showparts.do ... g=35&hl=32

[jimjambeal]

I'm to cautious to go poking and prodding around what I don't fully understand and only have the most basic of knowledge of.

I would have concerns that I would probably break more than I would fix.

I love my car, but am not a mechanic and am a strong believer in 'don't do what you don't do' and leave it to these who know - like yourselves.

[Grrrmachine]

Mitchen, there is no green sensor. The BROWN sensor drives the temp gauge in the cluster, which is number 13 (the one with a photo of a brown sensor next to it). 11 is the Blue sensor.

[Mitchen]

Lol I'm a div.. When the engines off, is there fluid in the thermostat housing? Is it just an unbolt and unplug job, or does the coolant all need draining?

[Brianmoooore]

Make sure there's no pressure in the cooling system by taking the pressure cap off and putting it back on again, and the amount of coolant that you lose will be about an egg cup full, but TEST the sensor at the ECU pins first!
The quickest way of turning a car with one simple problem into one that is a diagnostic nightmare is to start randomly replacing parts.

[jimjambeal]

Hi all,

Thanks a bunch for your suggestion Grrrmachine. I changed the coolant sensor (yes Brianmoooore, I changed it a˜‰), made a tweak to the MAF and she's running beautifully again.

This morning I'll be tackling adjusting the valves and she should run even better.

Thanks again to everyone for their input.

Jamie

[pianist]

MAF should be left alone no tweaks needed

[Grrrmachine]

Tweaking the AFM (it's not a MAF) is a bodge, not a fix. You now need to take the car to get the exhaust gas analyzed, get the AFM reset, and find the other cause of your problem.

It may well be that the ECU just needs to relearn its settings.

[Brianmoooore]

Hi all,

Thanks a bunch for your suggestion Grrrmachine. I changed the coolant sensor (yes Brianmoooore, I changed it a˜‰), made a tweak to the MAF and she's running beautifully again.

This morning I'll be tackling adjusting the valves and she should run even better.

Thanks again to everyone for their input.

Jamie

Now that you've disturbed things in the area, you may have temporarily pushed the possible corroded wires in the C191 together and replaced a perfectly serviceable OE temp. sensor (with an inferior aftermarket one?). The wires will continue to corrode and cause further problems, which may be unnoticeable, costing BHP and MPG, until they get severe.
You've also adjusted the AFM. Why? Is was set correctly at the factory, so all you've done is masked another BHP and MPG sapping fault.

[jimjambeal]

I apologies for the incorrect terminology.

I freely admitted I wasn't a mechanic and had little automotive knowledge. I was advised to adjust the AFM if needed, was not aware that this was not a part that should be adjusted and therefore won't be doing it again. It is evident that I was using a poor garage (who I won't be going back to) and I was told to get my hands dirty, which I did. I replaced (once again, I was not aware that the sensor could be serviced) the faulty part and the car is running great again.

I asked you guys because I wanted my car running as it should be and not condemned as another clapped out old BMW. I appreciate the advice you have offered, and also that your comments are for the well being of my car - but please take it easy on the newbie huh guys.

[Mitchen]

I think it's just because testing at the ECU before changing the sensor was mentioned a number of times, but fair play for giving it a try.

[jimjambeal]

That's fair enough.

If I'm honest, it was good to have a potential solution rather than just being told "try changing this or maybe that" and I just got into eager mode.

Following the the new sensor and valve adjustments all seems great, but if I do suffer any kickbacks from the work I've done then I guess that will be my karma for being to eager.

Every day is a school day.

[Grrrmachine]

The trouble is that the kickbacks won't show up unti the next MOT when you fail on emissions, by which time your wallet will have been stung by poorer fuel economy over thousands of miles. So even if the car feels good, take it to a reputable garage and get the exhaust gas analysed to ensure that the AFM is set to what it should be.

General rule on the Tech Forum is Do As Brian Says, to the letter. His advice is probably the only thing keeping most British E30s on the roads these days

[jimjambeal]

I do see your point and please don't think I was questioning anyone's judgement or advise. If it wern't for the suggestion from you guys I would still have the main problem is was experiencing.

I'll get it in with a BMW/Merc specialists local to me after the Easter weekend to get the AFM checked and keep a close eye for any repercussions.