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R

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Discussion Starter #1
Hi all,
A couple of weeks ago I posted a problem with my 155 2.0 8 valve which I'd thought I'd traced to a poor connection to the Lambda sensor. Well, the problem has come back. I've fitted a new sensor and I've replaced the large inlet hose because it had a split in it, but its still the same. These are the symptoms:
1. Idle speed is surging a little – 850-900rpm at idle.
2. Part/light throttle gives big hesitation - worse when cold but still there when warm.
3. Popping on overrun.
I've checked thoroughly for air leaks and I've cleaned out the idle air valve. I've disconnected the battery overnight for ECU reset. Still no different.
I have a question regarding the Lambda though. The wiring from the car's system on mine has one Bosch type connector (two white wires-ECU?) and two loose wires - I guess this is from a previous aftermarket sensor which didn't have the Bosch type connector. Anyway, there doesn't appear to be any current going from the loose wires (which I'm assuming is to the heating element in the Lambda and are coloured green and black (car) to white and black (Lambda)). There is current going into and out of the fuse but where it goes after that I haven't a clue.
Sorry if all this sounds fuzzy, but if someone has any ideas I'd be grateful.
Cheers
Rob :confused:
 

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Correct, the two whites are the power to the heater.
No heater means poor readings when cold. May be the cause of the problems, especially the sloppy idle.
Have a look at http://www.lambdasensor.com/main/mcolours.htm and this has the pin-outs.

Oh, and if the split in the hose was after the air filter, consider changing your engine oil. Any dust/dirt will be caught in it.
 
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Discussion Starter #3
We have just solved a problem on a 155 2.0 8 valve and as you put in your post it was the large inlet hose because it had a split in it so if i was you i would spray some wd40 around the inlet hoses and inlet manifold and when it changes tune you have found the leak.
Sorry i can't help anymore.

Ted
 

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Gulp... WD40 may be OK for use in this way, but make sure that the product you decide to spray doesn't contain silicon. It kills lambdas.
There is a product out there for spraying on intake rubber, it also dries out after a few mins, not like WD40. Don't know the name of it though!
 

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It sounds almost identical to Marlons problem he was having...............turned out to be the fuel pressure thingy :rolleyes: try a search theres a thread on it somewhere :D
 
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Discussion Starter #6
If all else fails have a look at the coil packs, they split open causeing a missfire particularly when cold.
 

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OK, some assumptions. Firstly, that the heater circuit is correctly wired and receiving current at all times with the engine running. Secondly, that the Lambda signal wires are securely and correctly connected to the loose wires you have in place of the AMP connector. Unless you are trying to measure microamps, you won't see any current on the signal wires - try measuring the voltage across them with the engine idling - you should see something like 0.5v that fluctuates a wee bit and will jump to about a volt when you blip the throttle. If yes, then the lambda is doing it's thing. You need to measure this with it all connected up and using a decent DVM by the way.
 
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Discussion Starter #8
Guys,
Thanks once again for all your input.
I can't find any other air leaks other than the split main hose but I'll keep looking.
The kangarooing on light/part throttle seems worse during warm-up although it's still there when its warm. When you boot it, it goes well, whereas before the split pipe discovery, it didn't feel so smooth.
One thing I did notice when I replaced the lambda was that the old one was covered in black soot. I don't know when it was last replaced - but would that be a normal colour? (i'll try and get a pic this evening)
The coil packs look fine- no evidence of any cracks at all.
I can see this ending up at the local Alfa specialist for a diagnostic check.
Cheers anyway
Rob
 

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A light deposit of black soot is correct and nothing to worry about.
 
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