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Discussion Starter #1
Hi,
Just had my 2.0 147 diagnosed with a failed 'Cam-shaft positioning sensor'. This was after the 'motor system failure' warning light randomly came on. Took it in for a diagnostes on a machine and this was the problem listed.

Garage quoted me £190 to change (parts in) but wondered if it was simple to do myself. Does anyone know if it easily accessable and a matter of replacing the part?
 
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You have to remove the cambelt. £190 is a very resonable price. Just make sure they have cam locks. It may also be worth considering having the cam belt, idler, balance belt, tensioners and variator replaced too.
 

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It's cam belt off and exhaust cam pulley off, I'm afraid. Because of the cam lock tool, it is cam cover off also. It could be a very good time to have the cam belt and tensioner etc changed at the same time- as just said. If your car is a 1.6 it will be cheaper. If it is much above 50k, it could also be worthwhile changing the variator as they usually become noisy about this mileage.
 

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Discussion Starter #4
Thanks guys,
Just got of the phone to Auto Lusso - very helpful!!

Basically they explained that for the sensor to go is very unusual and actually my problem is more likely to be that my timing is out, as the cam belt was only changed a couple of months ago. This was done by the garage when I bought the car, so I need to investigate if this was done correctly. The sensor is probably not faulty and doing its job warning me!

I don't think the garage who said the sensor had gone realised when they gave me quote the work it would entail - one hours labour was the quote!
 

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Quite possible the garage has buggered the sensor by distorting the ring on the back of the exhaust camshaft sprocket that runs in between the jaws of the sensor. There's not much room for error.

The sensor's quite easy to test, but needs to be hooked up to an oscilloscope (or similar).
 

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Discussion Starter #6
Thanks. I will take of the plastic cover of the cambelt and see if the 'old tipex timing set up' was done as advised by Auto lusso. I will also contact the garage to find out if the cam locking tools was used to do the belt changes properly.

I guess I won't know if the sensor is damaged by sight?

Is there anything I can do myself to correct/diagnose this problem? or is it a timing test/sensor/cambelt change (again) by a garage?

Is it OK to drive for the short term and any idea of costs?

Thanks alot for advice, any more info would be much appreciated.

Thaks again everyone
 

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You can't really see the sensor too well when it's installed. You could look on the sprocket ring and see if you can see any tell-tale marks that indicate it's been hitting the sensor.

The sensor itself is about £60 from a factor, double that from Alfa. To change it requires taking the timing belt off again, which should really be renewed rather than replaced (if it's done a handful of miles, I'd be inclined to risk putting it back on, but it's only £25 to avoid the danger). If the sprocket's damaged, a new one is £30 ish (I got mine from ebspares).

The water pump needs to be taken out slightly, so again it's a toss-up whether you put the old one back on and risk it leaking, or go for a new one (£35 ish).

After that, it's labour, really.

If you want to save a bit of cash, I'm breaking a 158 1.8TS at the moment. The sprocket and the sensor should be ok on that, if it will suit your engine.

I don't think the failure of the sensor will adversely affect the engine. It will be an annoyance though ;)

Cheers,

Iain
 

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Discussion Starter #8
Thanks Iain.

Don't really want to have to replace all that if unnesecary, but if only way then will have to.

Auto Lusso (again the most helpful people) felt that it may be just the timing out. Over the phone they said I could buy the cam-locking tools if the garage hasn't fitted it right myself, but i'm not really sure - does this still entail replacing cambelt (or more)?

If so I think a garage is needed. But if the timing can be adjusted without them it may just save me a fortune (inc. time/hassle).

Annoying that before I bought the car (4 months ago) the independent put on new belts and variator so was good for another 35K and may have to replace again!!!
 

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There's no real adjustment in the timing, and only one way of doing it properly.

The camlocks go on the camshafts, a gauge goes down #1 cylinder to find top-dead-centre, then the belt is put on. There's a bit of adjustment in the sprockets to get the tension right, and that's about it.

You could have the timing checked without taking the belts off - using the camlocks and gauge and take it from there.

I'd be a little surprised if the timing being out would cause the error code. In my experience, when the sensor is damaged it stops outputting a nice square wave and gives out a constant 12V.

If you've got access to an oscilloscope it's easily proven...

One of the sensors I had was ok until it got a bit warm, then it played silly buggers! It was damaged by a non-circular sensor ring.

Where about are you?
 

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Discussion Starter #10
In the sticks - North Devon to be precise.

Warning comes on when cold or warm. It also sometimes doesn't come on when cold or warm. Any weather it can or not come on. Sometimes comes on when car used repeatedly or maybe not at all, even when used, for a couple of days.

No real pattern to it but does seem to be happening more often over the last few weeks.

How do get access to an oscilloscope (do most garages have one?).

I think a call to the original dealer I bought from maybe a good place to start or a local garage for a check on the timing and the oscilloscope test on the sensor to narrow down?
 

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If it's intermittent, it may just be a bad connection (perhaps it was disconnected during the belt change). Not sure about your engine, but looking towards the back left of it from the front of the car there may be a blue 3-pin connector. Check that...

You may need to remove the plastic engine cover to see it...

Oscilloscopes... Hmmm... I borrowed mine (permanently!) from my PC supplier who no longer had a need for theirs. Not sure...schools, colleges...local electronic companies....
 

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Discussion Starter #12
OK great i'll have a check at the weekend. Seems a good look over may be in order and go from there.

Have quite a large IT department at work and i know a technician that might be able to help with oss.

Thanks again
 

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I dissagree and think the sensor is working. A decent disgnostic specialist could hook up a scope and show a wave form, or not, in minutes. I'm sure the engine wouldn't run if the sensor was gubbed because it wouldn't know which of the cylinder pair was on power stroke rather than exhaust stroke. I think the system has simply detected an anomally with the timing and thrown an error code.

I think the exhaust cam timing is out, or both. If the tensioner was changed before, then, with care, you could get away with simply resetting the timing. The belt will likely have to come off the top 2 pulleys for this, and it is perhaps inadviseable to risk a used belt.

I also think the TS coolant pumps are better than people give credit for. My sister's 155 is on 172k with original pump. However, in your case, a quick look gives piece of mind, but that means a coolant change.
 

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My 2.0TS ran and started fine with a completely shafted sensor.

Makes you wonder why they're needed...!

The exhaust cam timing is altered by the variator...so maybe once that kicks in the timing is out by more than the ECU would prefer it to be... Drive around at under 3,000 RPM and see if it stays off....!
 

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The exhaust cam timing is altered by the variator...so maybe once that kicks in the timing is out by more than the ECU would prefer it to be... Drive around at under 3,000 RPM and see if it stays off....!
It's the inlet cam timing which changes.:lol: But you already know that.;)
 

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Discussion Starter #17
Going to check all this out as suggested.

Just as a note, since I picked the car up after the diagnostic (and sensor problem diagnosed, which I didn't have fixed), 4 days ago, the car has been running fine with no warnings at all!!.

(This just maybe because of the battery being disconected or a re-set?)
 

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Discussion Starter #18
Update: Put car in to have 2nd opion diagnosis and same sensor problem came up. Had this replaced and was told that belt was out as well. Not sure if this was the real problem or sensor needed replacing aswell but car runs fine now with no warnings.

This was obviously up until tonight when my coolant temperature went beserk! (please see other thread - any ideas would be appreciated)
 

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Same fault came up on my GT 2.0 JTS today.
Put it on diag,reset it,removed the socket & reconnect it.
Then, drove for about 5 miles with a top speed of 170km & nothing came up.Was it a matter of reset? Is that it or is it possible to come up again?
P.S. my engine has just 9000kms on the clock!
 

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OK great i'll have a check at the weekend. Seems a good look over may be in order and go from there.

Have quite a large IT department at work and i know a technician that might be able to help with oss.

Thanks again
If you like I have time on sunday now that I would be able to change the sensor for you, I even have a good sensor sat here. PM me if you like.
 
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