E30 Zone

I've got a 535i engine in my sport. A 1991 model.

When I started her from cold shes fine but after 5, 10 minutes of her heating up she starts this misfire and severe chug. Basically shes not firing right and what seems like going off a cylinder as soon as I try to accelerate.

Then I stripped the front of the engine, radiator hoses etc to get room to remove and replace the CPS.

So after a lot of stripping back and cleaning parts for a bit of a clean up I reassembled everything. The misfire and chug is no longer a problem as the engine won't even fire up.

I churn and churn the car but she won't fire up. I replaced the CPS and this was the outcome. So I put my old sensor back in but still the same. No firing at all and the engine is getting fuel so I can rule that out.

So I'm thinking its the coil or the HT Leads. The coil is getting power but there doesn't seem to be any power from the HT Lead coming from the Coil or any of the HT Leads for that matter. I was using a rig with a bulb to test for power from the coil and the leads. I'm a bit stumped so any help would be great.

OK so I tested the spark and she is sparking so again I am lost as to what is up with the car. Obviously if she is sparking the coil and leads must be fine. The car just wont fire up.

Any more ideas?

Retrace what you stripped down, what exactly did you remove to replace the CPS? Did you remove any engine earths?

mcbonio wrote:Retrace what you stripped down, what exactly did you remove to replace the CPS? Did you remove any engine earths?

No I didn't mate but I found out what was wrong it was a broken temperature sensor. I was broken during the re-tightening. But now I am back to the old problem, here's a quick update.

**Update**

OK so the car wouldn't start at all it lead me to a broken temperature sensor. It must have got broken in the tightening of it as the blue connection itself had come off the probe part of the sensor.

So with this done she started but still wanting to die as soon as you apply revs and even misfiring slightly on her own as she heats up then she will chug and chug before she slowly dies. And then will not start she would have to be left for a good while until cold and then she would start but with the same outcome.

I have also replaced the crank sensor with another that I have but I would maybe be better to order a new one.

Anyone else had this happen them? I'm really stumped

i had a very similar problem with the bad misfiring once i got up to temp, replaced plugs and leads (which 'looked' fine) and the problem was gone

something doesn't have to look obviously broken to cause a problem!

if you have a bad lead which may be earthing randomly to the head it can make it chug at tick over, and then when you accelerate and put it under load the spark will take the easiest route out, which can be wherever its earthing to the head!

i know m30 leads aint cheap to replace if they may not be a problem so try having a look at the engine running in the pitch black to see if you can see a lead earthing somewhere!

Have you got a multimeter to test components rather than just replacing them?

Yep I have a multimeter just not sure what to check. I put in a new exhaust manifold and gasket as it was a job I needed to do any way along with the temperature sensor. I'm just looking now to find out why when its cold it starts and when its hot it wont and the rough running in between. A real pain to get to the bottom of.

So far its only cost me £9 and a whole load of heartache

Black_Op_88 wrote: I'm just looking now to find out why when its cold it starts and when its hot it wont and the rough running in between.

like i said mate, that was exactly my problem!

dubwonerbilco wrote:

Black_Op_88 wrote: I'm just looking now to find out why when its cold it starts and when its hot it wont and the rough running in between.

like i said mate, that was exactly my problem!

Shame I couldn't get a 2nd set to try. They cost around £150+ for a set with the sensor part. They joys of motoring.

i bought these ones mate, they didnt have the extra sensor thing, its not essential anyway, but they seem like reasonable quality to be fair!

http://www.ebay.co.uk/itm/230875086722

dubwonerbilco wrote:i bought these ones mate, they didnt have the extra sensor thing, its not essential anyway, but they seem like reasonable quality to be fair!

http://www.ebay.co.uk/itm/230875086722

I wasn't sure about the sensor fitment that's why I wasn't sure about them working or not.

Put up a wanted ad, I got a great OEM used set off Rav for cheap. You can use m20 leads too.

Or test them with a multimeter, if the resistance measures more than 7k ohms then you have a problem.

mcbonio wrote:Put up a wanted ad, I got a great OEM used set off Rav for cheap. You can use m20 leads too.

Or test them with a multimeter, if the resistance measures more than 7k ohms then you have a problem.

Cheers pal will do this tonight and get back to you.

Like dubwonerbilco faulty leads were the main cause of my m30 running badly, i'd test the ones you have on the car first before shelling out though.!

OK so I got another set of leads to try and see if it helped the situation. Well the car starts but seems to be off a cylinder. It defiantly doesn't misfire as much, in fact hardly at all but it is off a cylinder and then will die and refuse to start. I've a fresh set of spark plugs here so will try them tomorrow but really the jury is out I'm lost to what could be the overall problem.

Sounds like you need to do a compression test, to ensure all six pots are giving more or less equal readings - anything of 160 psi upwards is what you're looking for.

Speedtouch wrote:Sounds like you need to do a compression test, to ensure all six pots are giving more or less equal readings - anything of 160 psi upwards is what you're looking for.

Dam I'll be needing one of the wee testers, must get one from the motor factors tomorrow, there not expensive around 15 pound.

Indeed, and a very useful bit of kit to have. I've had a Gunsons one for years, and it's still working well.

Speedtouch wrote:Indeed, and a very useful bit of kit to have. I've had a Gunsons one for years, and it's still working well.

Will get one tomorrow and report my results. Thanks man.

I'd still be tempted to overhaul your ignition system, this seems to be an common m30 issue for poor running. Plugs, dizzy cap, rotor arm and leads. You can use m20 parts on the m30 engine too.

OK I replaced the spark plugs and still no difference. I have got the hold of a compression tester so I will be doing this tomorrow. As for the ignition system the dizzy cap looks fine and unless I could pinpoint as the single cause of the problem I don't fancy shelling out for it.

A real pain this has turned out to be.

OK so did a compression test and there seems to be plenty there well within the region if my tester is to be trusted. Does anyone have the firing sequence encase I have the plugs fitted to the wrong part of the dizzy cap.

The firing order of the M30 is 1,5,3,2,4,6.

There should be numbers on the dizzy cap near each terminal.