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Discussion Starter #1
Hi everyone this is my story so far... Got the car about a month ago, had a bit of dodgy idle so it came with a new MAF sensor. No real problems apart from the idle, still ran ok. Tried the new MAF no better, maybe worse and have tried unplugging it and it dies. Occasionally have a loss of power with jerkiness on throttle and has also cut out on me a few times, pretty dangerous joining a busy road but doesnt always happen though. So far have unplugged the lambda with no joy, will try cleaning the throttle body and the BBOB relays... Anybody have any ideas as im losing patience and may just take it to specialist - thanks for any help. :thumbs:
 

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Could be idle control valve or your belt has skipped a couple of teeth...
 

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Is yours an alloy or plastic topped engine? To cure the cutting out it would be worth checking the crank sensor when it's hot.
 
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The best thing to do IMO, is to get it "plugged in" which will highlight any actual fault codes as opposed to educated guesswork.
 

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Discussion Starter #7
It is a plastic topped engine, how would i go about checking the crank sensor? I may take it to a specialist who do the fault codes etc, awkward when you live on an island. :lol: Or might get a new idle control valve.
 
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get it plugged in before you buy anything - it'll save you spending in the long run.
 

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On the plastic topped engines with the MAF unplugged the injection warning light on the dash should come on and MPG will be appalling but the car should still run. According to the Bosch M1.5.5 manual if MAF ouput is out of range the ECU just comes off it's map and looks at the Throttle Position Sensor for input.

As yours is plastic topped the TPS is in the same assembly as the Idle Stepper Motor anyway. There is no seperate idle air temp valve. The Bosch part number for mine was 0.132.008.650.

Therefore assuming your BBOB is all ok and there's a constant live feed, cutting out would imply from your combination of symptoms that you have at least an intermittent problem with either the crank or throttle position sensor.

As Rosso says if you go to someone with diagnostic equipment they should be able to tell from stored fault codes in the ECU. And he's right that there are other far less common faults which can cause similar symptoms which you do need a good amount of electro-mechanical experience to find and fix.

However 90% of the time the problem is with 1 of those 2 sensors. If you want to fix it yourself I would check the crank sensor when hot as the first possible culprit then the TPS. The cost of both parts is about £100 from most motor factors so you can compare that with what a dealer will charge for diagnostics and the parts.

If you do need a TPS then either you need a dealer to reprogram the ECU to match it or drive around with possibly a few minor throttle glitches or poor MPG for a few months while the adaptive ECU's on these engines re-learns
 

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Discussion Starter #11
Ok thats very helpful. I will check them when i have chance, it sounds possible as it can run fine at times then just bog down or try to cut out. How would i check the sensors? Thanks again
 

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yes it will be the idle control valve, this will cause jerky running at varios speeds in most gears under slight acceleration, and it will cause an eratic idle, on some cars its always, and on others it happens a lot but not neccessarily all the time, if you get it plugged in at an alfa specialist, they will do a reset. all the reset advice i have tried to do myself was all rubbish, didnt work. good luck
 

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Discussion Starter #13
Ok thanks for everyones help, looks like it most probably is idle control valve and expect the best option will be to get it done properly at a specialist. Got next week off work which makes things slightly easier! ;)
 

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On the plastic topped engines the Idle Stepper Motor only controls tickover and trickling along on almost no throttle up to 1800RPM. Indications of a faulty one are bouncing idle RPM and jerky running in walking pace traffic.

Because of Toms symptoms I'm almost certain he has a TPS problem.
1) When you put your foot down from standstill and the MAF can't keep up with the suddenly increased airflow the M1.5.5 ECU looks at the TPS to judge the amount of fuel needed instead. Under these circumstances his car cuts out.
2) When he unplugs the MAF the engine dies.

A simple way to test this Tom would be to pull away without putting your foot down hard, only use very gentle acceleration until the car is up to at least 20MPH. If that stops the cutting out then it will confirm my suspicions.

If you have a quality multi-meter then you can measure the impedence of the TPS pot on the end 2 of the 6 pins in the connector, it should change slightly if you turn the throttle by hand. I've just checked my spare one and it varied from 23 to 24.8 Ohms.

Either that or find a Bosch specialist and see if there is an error code for the TPS stored.
 

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Discussion Starter #15
What i've found is that it is pretty random as it didnt die today, just stuttered a few times, mostly under heavier throttle and sometimes just slight acceleration. As i came to park it was on the verge of cutting out though. I'll try measuring the TPS, whereabouts would I find it, is it on the throttle body?
 

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Yep on the back where you need a double jointed gynaecologist to get to it lol. Here's a pic from the manual, hope it helps.

If your car cut out randomly but mainly when it was warm I'd suspect the crank/RPM sensor. They are common failures and only cost £30-£40.

It's the fact that you said it does it under acceleration, especially from standstill and always when you unplug the MAF that makes me suspect the TPS.
 

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Discussion Starter #18
Yep on the back where you need a double jointed gynaecologist to get to it lol. Here's a pic from the manual, hope it helps.

If your car cut out randomly but mainly when it was warm I'd suspect the crank/RPM sensor. They are common failures and only cost £30-£40.

It's the fact that you said it does it under acceleration, especially from standstill and always when you unplug the MAF that makes me suspect the TPS.
Yeah I get quite paranoid when pulling away from junctions, although it hasnt died for a couple of days now and last time was when i was just stopping to park. At the moment just noticing the odd stutter and jerkiness when slowing and apllying throttle (kind of kangarooing but not severe). If it does though i'll make a note of the temerature. :thumbs:
 
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