WHY IS MY CAR DOING THIS????

[oz-boz]

Whatever the problem is it seems to be temperature related, from cold start as its only doing this when temp is below 12/13c

Engine cranks straight away & idles for 20/30 seconds before the revs suddenly bounce from 1000 to 500 and back with what sounds like a click/knock sound.
As it does this the yellow triangle, red battery and oil light flash very briefly, less than half a second. The EML and engine light comes on and goes out after 2 seconds, the same as if you just started the car.

https://www.youtube.com/watch?v=5mFBfdVVXY8

It will do this 2/3 times until it appears the engine temp is midway in the red. it will then start and run fine all day.

I have attempted to just start the car and go. It didn't stall but still did the cough thing where the revs suddenly bounced to 500 and back. I had the handbrake light and yellow triangle come on and stay on. Pulled over and restarted it, no lights, ran fine rest of the day.

I've had the icv cleaned, new disa, thinking new camshaft sensor, coolant sensor, maf cleaned and DME re-programmed/flashed.

I've had the garage check for air leak but couldn't find one, although today i could hear when i rev the engine, a kinda "air sucking" noise in the slight delay before the engine reacts to the pedal and revs... normal or air leak maybe?

I never have a problem when its warm, it never wants to stall. its been fine all summer.

I hope someone can offer advise on this, I've only just bought this car, I don't want regret blowing my savings on it... its getting that way

Thanks.

 

[aquazi]

You've checked the main bits... Presuming the maf isnt faulty, but if it runs fine for after its warm then it must be ok.

What petrol do you run it on? Might be fuel related... Could be worth giving it a tank of decent fuel and seeing if that clears it.


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[srhutch]

Have you had the codes read?

The noise you are hearing at 500rpm is the anti stall I would think.

 

[Jasey]

Could be worth giving it a tank of decent fuel and seeing if that clears it.

Or even putting a little bit more in anyway - running pretty low on the video - could be pulling in all sorts of shite into the engine.

Having said that the symptoms and your efforts so far would suggest something else

 

[simonlpearce]

I would very much doubt its fuel. Bad fuel is more of a myth these days to what it used to be, plus we have filters to filter out any crap.

I would re-check all the intake boots. Take them off from the MAF right back to the throttle body and properly inspect them.

Also try unplugging the MAF and starting the car from cold to see if the problem is still there. It should revert to a standard map with the MAF unplugged.

 

[andrewr]

A dying battery can cause all sorts of issues, how old is the battery?

Andrew.

 

[-Tom-]

A dying battery can cause all sorts of issues, how old is the battery?

Andrew.

Maybe a short somewhere ... Earthing issue? Checked your battery tray hasn't flooded too?

 

[oz-boz]

Thanks for the replies people, any advice is much appreciated.

Filled up with tesco momentum today as I've been using Morristons crap until now. No shell garage for 25 miles.

I cleaned the MAF with contact cleaner, visually checked all the rubber boots and used carb cleaner to check for air leak, but couldn't find any.

I changed the air filter while I was there too & that was really quite dirty.

I did notice a vacuum pipe seemed kinda sucked in on itself a little. oval shape in certain places rather than round if you know what I mean? The fat coolant pipe of the rad seems quite soft and squidgy too... Not sure if this is normal??

Car seems to idle more smoother now, needle is more stable and i can't feel the idle through the car so much as I could before.

Not sure how old the battery is bit looks like the original bmw one, shows a green light on it. I do alot of small journeys as work is only 6 miles from home. May get that checked tomorrow.

Got it booked in Thursday for a full scan and dme re flash with the latest software.

I've still yet to sort out the suspension so I'm hoping this will fix things and not eat all my cash.

One last thing, does anyone have a pic of where the sound generator is and where to pull the pipe out to get to the sponges?

Thanks.

 

[Stratts]

Filled up with tesco momentum today as I've been using Morristons crap until now. No shell garage for 25 miles.

I cleaned the MAF with contact cleaner, visually checked all the rubber boots and used carb cleaner to check for air leak, but couldn't find any.

I changed the air filter while I was there too & that was really quite dirty.

All of the petrol comes from the same refinery, don't worry too much about where you buy it from. Sure, Shell and BP add some extra additives, but nothing that will affect your engine. Supermarket stuff is fine.

Sounds like some of the other bits may have helped, the MAF clean will usually give a quick improvement, hopefully not too short term, and the air filter too. Any issues with air flow will cause your symptoms o maybe you've helped a bit.