E30 Zone

I have had some problems lately with my M30 engine. The 535i is sometimes missing and chugging. For instance last night I was at a set of traffic lights. As I pulled away and went to go into 3rd gear and increase acceleration the car chugged and misfired. The harder I put the foot down the worse it got and the slower the car got. I went down to 2nd and cruised easily but when I wanted a quick burst of speed the car was sluggish, misfiring and chugging.

I got to where I wanted to go within 10 mins of leaving the house. And after about an 1 hr 1/2 I started the car again. This time there was no problems. I was even able to open her up going up the motor way.

I'm wondering what it might be as I often do a lot of my work myself along with my dad. The car has recently had a new Lambda sensor fitted and coolant temperature sensor fitted as well as some new air hoses as I had a rough idle for quite some time. That has now been fixed.

But now this problem has arose.

Any help guys?

Could be anything but i would start with the simple things first such as plugs or leads and dizzy cap and fuel filter then your fuel pump pressure or even crank sensor could be playing up, could be anything really just start changing and test driving till its fixed good luck

Time to get a multimeter off ebay

I had this happen on my first M30 and it was behaving like you described, would idle fine but would occasionally bog down when i floored it (mainly when it was hot)
Turned out to be the air flow meter.

first check the air flow meter flap isnt sticking then pop the plastic lid off and see if the carbon tracks are worn, you can go a step further and get a 9v battery and mutimeter on the plug to see if it checks out.
Ill post back of which pins the multimeter has to go on.

Check Throttle position sensor too.

Well today I changed the fuel filter, so fingers crossed that's it but knowing my luck it won't be. I'm going to take some photo's to keep yous interested, even if it is a silly we hunt for a problem

Here's how to test the AFM.

http://www.e30zone.net/modules.php?name ... highlight=

E30SPORTMAD wrote:Could be anything but i would start with the simple things first such as plugs or leads and dizzy cap and fuel filter then your fuel pump pressure or even crank sensor could be playing up, could be anything really just start changing and test driving till its fixed good luck

Not sure this is not the best advice really, throwing new parts at an intermittant fault could turn costly, new crank sensor at 90 quid only to find the fault is still there isn' t the best solution surely?

johnl320 wrote:

E30SPORTMAD wrote:Could be anything but i would start with the simple things first such as plugs or leads and dizzy cap and fuel filter then your fuel pump pressure or even crank sensor could be playing up, could be anything really just start changing and test driving till its fixed good luck

Not sure this is not the best advice really, throwing new parts at an intermittant fault could turn costly, new crank sensor at 90 quid only to find the fault is still there isn' t the best solution surely?

New parts don't do no harm to change atleast you know what you have in the end but if your just wanting second hand parts to try/buy give sskoda on here a PM as he has a few runing cars there for breaking and is based in N.Ireland aswell

I agree, they do no harm at all but how about actually diagnosing the problem rather than chucking parts at it, you be pissed off with a garage that had spunked 200 quid on parts only to tell you it was still fooked.

Well i think this guy wants to fix the problem himself so if he doesn't know what he's looking for is it not best for him just to try other parts to diagnose the problem? If i was working on the car i would only be charging for what part cured the problem but maybe garages over your way work different

I'm just not into throwing money at an old m30 lump when it could be something ad simple as a poor fuel pump fuse connection.

Have you had the Dizzy off, and looked at the rotor too.?

Well just over a week now after fitting a fresh fuel filter. It's still there.

As I have said this is an intermittent problem, comes and goes. But just this morning I was going into town and the car was fine. Stopped, did what I had to and on the return leg it was chugging again.

I did notice that when it first fired up the start was rather shaky, I felt it through the whole of the car. Then it was chugging and missing but only if I was wanting to put the foot down If I accelerate very slowly the engine seems to come a lot better.

Im happy enough changing parts at the moment, preferably the cheapest ones but if I can fix this myself it will be an education for me and a bleemin relief

I have heard that the problem could be a broken down HT Lead expanding when hot. I don't think its the crank sensor because the car isn't cutting out. Before this all happened the car over heated 2 or 3 times due to a broken water pump. Maybe that has done something?

Let me know what yous think. Has anyone produced an M30 conversion book by any chance? Could do with one my hearts broke. And before this I never had any bother.

Rav335uk wrote:Have you had the Dizzy off, and looked at the rotor too.?

No I haven't done this yet. Will probably be the next port of call what should I be looking for if there is nothing as evident as burnt connections? Residue etc?

Black_Op_88 wrote:I have heard that the problem could be a broken down HT Lead expanding when hot. I don't think its the crank sensor because the car isn't cutting out. Before this all happened the car over heated 2 or 3 times due to a broken water pump. Maybe that has done something?

Let me know what yous think. Has anyone produced an M30 conversion book by any chance? Could do with one my hearts broke. And before this I never had any bother.

Not good if it was over heated, what all did you get done to fix the over heating issue? may have annoyed something to casue your miss fire

Black_Op_88 wrote:

Rav335uk wrote:Have you had the Dizzy off, and looked at the rotor too.?

No I haven't done this yet. Will probably be the next port of call what should I be looking for if there is nothing as evident as burnt connections? Residue etc?

Yes, if it hasn't been changed before, I would change it for new all round

E30SPORTMAD wrote:
Not good if it was over heated, what all did you get done to fix the over heating issue? may have annoyed something to casue your miss fire

New water pump
New Thermostat
New coolant temp sensor

It was the bearings that had went on the pump but just changed the rest as they were cheap any way.

Fixed the problem and a few months later this other problem began.

Also wondering it could be a failing fuel pump. What do yous think?

Have you checked the AFM?

leeparkes wrote:Have you checked the AFM?

Yes I got a 0.64 steady reading. I am going to get my alternator check tomorrow. The reason for this is I have found that the more parts I turn on at idle the worse my car idles.

The car idles nicely but when I switch on my blower to full and lights and my electric fan the idle gets worse and worse with the turning on of each part. Also I often have a flat battery as I don't drive the car every day.

Im hoping I am nearing the problem.

Check engine to chassis earth strap and that there is no corrosion between alternator, its mount and where it mounts to, i have had a similar problem and so have quite a few e30's. Many a good alternator swapped because of this

johnl320 wrote:Check engine to chassis earth strap and that there is no corrosion between alternator, its mount and where it mounts to, i have had a similar problem and so have quite a few e30's. Many a good alternator swapped because of this

Will do that today as the test on the alternator and the battery showed both were fine. Will check this earth and report back. It is one of them wee niggling problems that I refuse to hand to a garage to be charged extortionate money to find a simple problem as I'm handy enough with the nuts and bolts of a car.

I will be grey haired by the time I get to the bottom of this.

I stuck my cicuit tester on the resistance setting and took a reading between the body of the alternator and the battery neg, It should be very close to 0.0 ohms but mine was in excess of 1k. However if you do get a low reading it still doesn't mean all is well.

On my m30 conversion I stuck another earth strap from one of the rocker cover studs to the chassis, close to the coil mount.

good luck

I'm already grey haired

Well I have tested all the earthing points but have found nothing wrong. I also cleaned all the earthing points to make sure but what I have noticed is the chugging has stopped. Although the car is now idling poorly, revving between 400-1200 rpm. Sometimes almost dying completely.

Any suggestions?

I myself am going to check the seal on the dip stick and the CPS.