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Discussion Starter #1
Hello forum :)

Im having problems with my 2000 156 V6.
Basically it has problems starting and when it does start, it is hesitant and unresponsive.
Plugging in Alfadiag, which showed 3 fault codes relating to Crank Sensor, Timing Sensor, and Air Temperature Sensor.
The MAF had been changed less than a year ago and so the crank sensor was replaced, but with no luck. The Timing Sensor was swapped for a known good one, and all the wiring was checked for continuity between the various sensors and the ECU. Still no joy!
Off it went to an Alfa 'Specialist' who recommended changing the Timing sensor (again), and £200 later its just the same and could do no more.
Original Fault codes disappeared only to be replaced with a new one relating to Lambda Sensor 1 Bank 1.
Before I get underneath and struggle away changing this, has anybody else suffered similar problems.
Incidently all the relays in the front were swapped for known good ones so have ruled those out too.
Handily my friend has an identical car so I have been able to eliminate quite a few things by swapping bits, but all to no avail.
Problem does not appear to be fuel related, and their is a good spark at the plugs which are new.
Any advice on what to try next would be greatly appreciated.

Despairingly

Richard:confused:
 

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Spark at the plugs rules out the crank sensor and the timing sensor, the air temp sensor doesn't get aknowledged by the ECU during start up so that's out, If the lambdas heater has packed in then this will give you a dodgy start, but so will a dodgy temp sensor.

But for freebie quickies try cleaning the throttle body and doing an ECU reset, as you say you have Alfadiag you can do the reset on there in 4 minutes, afterwards start it and let it idle for 5 minutes without touching the gas, then go for a spin.
 

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You didnt mention if the timing had been dones by someone who knows what to do. I believe ECU errors on camshaft and tdc sensor can be thrown up when the timing is wrong as clearly the sensors will be indicating that they are picking up out of spec values. I have also seen a few tales on here of dodgy brand new tdc sensors from Alfa not making things better until they are replaced once again.

For the next bit Ive only done this on a 2.0TS (which in my experience is a safe test), so I am unsure whether it is valid/safe, so please dont take my word for it, usual disclaimer etc: If it refuses to start then generally its the TDC sensor in these situations that you describe. If you disconnect (via the plug) the camshaft sensor then it should start normally and run, but it will run in limp home mode thereby eliminating the camshaft sensor or not. For instance on my 2.0TS when the cmshaft sensor is disconnected it runs fine up to 3K revs and then it is rev limited by the ECU, but under 3K it is perfectly normal. I assume you have eliminated water/oil in the plug holes, cracked coil packs and a dodgy battery as these are some of the 3 most common alternatives to the sensors. Only other thing is dodgy earth????
 

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Discussion Starter #5
Thanks for the advice. The timing has been done by a pro so I hope it is not that. I think I will go down the earth route for now see how far I get with that keep you posted many thanks
 

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This could all be explained by a low voltage at the ECU by way of corrosion (unlikley as its inside the car on a V6) or a weak battery.
 

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If it refuses to start then generally its the TDC sensor in these situations that you describe. If you disconnect (via the plug) the camshaft sensor then it should start normally and run, but it will run in limp home mode thereby eliminating the camshaft sensor or not. For instance on my 2.0TS when the cmshaft sensor is disconnected it runs fine up to 3K revs and then it is rev limited by the ECU, but under 3K it is perfectly normal.
It limits the revs to prevent it hiting the point at which the variator is activated which advances the inlet timing 25', if the cam altered and the belt had sliped a tooth then in the nanosecond after the variator activated and the cam went through 20' you'd hear a clinking noise 4 times and then a huge loss of power followed by the engine just cuting out.

But by TDC sensor I guess you mean the CPS (Crank Position Sensor) this is actually measuring for 4' before TDC to combust the mix in the relevant cylinder.
 

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Ok, well I spent some time helping Blackdog (Richard) with his 156 today, but its still not running right. One of the codes it likes to throw up relates to the Oxygen Sensor, which we changed today, so to recap, we have now replaced Crank sensor, Timing Sensor & O2 Sensor, but despite clearing the codes with Alfadiag, we still get the following errors.

Failed Component Code: Timing Sensor
Fault Symptom: Above Maximum Limit
Warning Lamp Status: Warning Lamp Illuminated
Fault Test State: Test complete for this Error or not applicable.
Fault Code Storage State: Error Present at time of request
Event Count: 64 count
Filter Count: 0 count
Environmental Condition One: Engine Speed: 18 rpm
Environmental Condition Two: Standardised Load: 33.75 %
Environmental Condition Three: Engine Coolant Temp: 79.2 °C
Environmental Condition Four: Air Temp: 32.67 °C
Environmental Condition Five: Throttle Valve Angle: 3.441436 °
Environmental Condition Six: Battery Voltage: 12.5286 volts


Failed Component Code: Lambda Sensor #1
Fault Symptom: Below Minimum Limit
Warning Lamp Status: Warning Lamp not Illuminated
Fault Test State: Test complete for this Error or not applicable.
Fault Code Storage State: Error Present at time of request
Event Count: 64 count
Filter Count: 0 count
Environmental Condition One: Engine Speed: 18 rpm
Environmental Condition Two: Standardised Load: 26.25 %
Environmental Condition Three: Engine Coolant Temp: 97.3 °C
Environmental Condition Four: Air Temp: 47 °C
Environmental Condition Five: Throttle Valve Angle: 2.502862 °
Environmental Condition Six: Battery Voltage: 13.9416 volts

Since fitting the O2 sensor the car does seem to idle a little smoother (thats after we have actually managed to start it), but it is still hesitant and rough, especially under load. Almost sounds like its the MAF again but no codes show up. Will swap our MAFs to rule this out over the next few days, but I think we are just clutching at straws.

Re: Cambelt jumping a tooth, I think the Static Timing is ok, as the car will, when it feels like it run beautifully smooth.

Its a tough one!:confused:

Richard (No.2)
 

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FOr the timing sensor why the battery voltage at 12.5 in comparison to the other warning at 13.9416??? when both were logged during turnover at 18RPM?
 

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Hi Doc G

Have to say we didnt notice that change in voltage between the errors.
Could this be significant?
Battery is also new.

Richard
 

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Difficult to say. Battery is one of the common causes of problems also, but the voltage is not below 12V so I suspect the battery is okay. However, alternator is a possibility and that is a nightmare so give it a thorough test before even thinking about it and get some advice from people with experience in that area (I have none). Once running you should have a voltage between around 13.9 and 14.5(max) if the alternator is okay.
 

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Environmental Condition Four: Air Temp: 32.67 °C

Environmental Condition Four: Air Temp: 47 °C

Come on, it's not that warm in Notts this time of year, That sounds like the MAF is duff to me, the air temp sensor side at least. Warm air, more fuel, flooding, lumpy, lambda readings try to correct but go out of limits. Engine stalls.
 

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Environmental Condition Four: Air Temp: 32.67 °C

Environmental Condition Four: Air Temp: 47 °C

Come on, it's not that warm in Notts this time of year, That sounds like the MAF is duff to me, the air temp sensor side at least. Warm air, more fuel, flooding, lumpy, lambda readings try to correct but go out of limits. Engine stalls.
I get the same on mine when she is sat still with alfadiag running, the air inlet piping and maf quickly heat up due to the engine bay ambient temperature being high. I assumed it was normal as once you drive again the temp goes back down. The log is admittedly a bit weird above between the two sensors, but perhaps the environmental condition captured was for the 64th value and not the 1st... for the lambda.
 

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Car is now fixed and running beautifully!

It would seem that the 'specialist' who changed the cambelt had not fully tightened the bolt on the inlet cam pully, which was causing timing problems. Wont be going back there again!

The fault was diagnosed & rectified by Andy Blake (Northampton) who I can highly recommend.

Thanks to all you guys who posted a response.

Cheers

Richard
 
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