Mattb
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Registered: 2nd Feb 03
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if your cam belt is out even one tooth you will bend valves........if the cams are worn, they will not open the valves for long enough, causing the engine to run lean, which will be sorted by the ecu, by pumping in more fuel (may store a fault code saying the adaption limit has been exceeded) but at high revs volumetric efficency will be decreased, causing a lack of power......
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Mattb
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quote:
Originally posted by MoNkEy MaGiC
my Gsi DRINKS oil!
so if the piston rings were fuked is this all that cud cause this ?
[Edited on 26-11-2003 by MoNkEy MaGiC]
it could do, may also be valve stem oil seals, if you are over heating aswell could be you're head gasket. may have a leak somewhere also....
got a second opinion on my gsi today.........the top piston ring as warped, letting oil past, probably caused by massive over heating, pistons are shagged too........throwin away my engine coz its fooooooked!!!
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miles
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Registered: 25th Mar 02
Location: plymouth Drives: Astra Sport
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I see your signature is true 
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Mattb
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tankyou 
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miles
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Registered: 25th Mar 02
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At least you know it
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Mattb
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but its true sh*t
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miles
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Registered: 25th Mar 02
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You can get away with being more that 1 tooth out, infact I've been 3 out before on one cam
Why would worn cams cause lean running?
How would the ecu know its running lean under load?
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Mattb
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mmm probably could get away with one tooth, depends on the engine, and valve lead/lag, the gsi i belive has quite alot of lead. i have a friend who had two teeth out resulting in a few bent valves.
worn cams would cause the valves to open for a shorter duration of time than normal, perhaps my wording was bad, it wouldn't be a case of running lean really, but more of a case of not enough fuel/air mixture entering the cylinder on the induction stroke......ei poor volumetric efficiency..
as for how the ecu would know if it was running lean......it takes readings from the throttle position sensor so it knows what kind of load the engine is under eg half throttle, full throttle etc, readings taken from the crank position sensor tell the ecu how fast the crankshaft is revolving so it can compare it to the position of the throttle for example
throttle fully open, engine speed low, therefore the ecu knows that you want to accelerate, and injects more fuel accordingly (full load usually sees an air fuel mixture of about 8:1) the lambda probe in the exhaust will mesure the level of hydrocarbons leaving the engine determining if too much fuel is being injected telling teh ecu to adjust the amount of fuel accordingly (because the lambda probe doesn't just mesure oxygen)  
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miles
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Registered: 25th Mar 02
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Im talking about a 1.4 16v, my old one was 3 retarded, 2 advance
I was going to say, that with worn cams, you would indeed get less fuel into the cylinder, but obviously less air also, hence not lean, just not maximum efficiency as you said.
Isn't closed loop only functional at part throttle?
You seem to be more knowledgable than I gave you credit for, knowledge can be a rare thing on here
[Edited on 05-12-2003 by miles]
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Mattb
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closed loop only really applies at a constant speed, on acceleration or deceleration, open loop applies....
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miles
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That was my point, so at other than constant conditions how does the ecu monitor afr? Or does it still use the lambda sensor for this in open loop?
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Mattb
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on open loop i don't think the ecu fully ignores readings from the lambda probe.
not sure tho, and i lied about the air/fuel ratio under full load, its more like 11:1......8:1 is cold start....doh!! 
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CorsaBNor
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Registered: 5th Apr 02
Location: Norway
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EGR valve. 
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Andy
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Registered: 28th Dec 99
Location: Cumbria, UK
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quote:
Originally posted by miles
That was my point, so at other than constant conditions how does the ecu monitor afr? Or does it still use the lambda sensor for this in open loop?
On open loop, ECU will ignore lambda signal; will instead rely on internal map, based on throttle position sensor and engine rpm. Some ECUs run closed loop all the way to full throttle (ie look for lambda input). Others run closed loop only to around 3/4 throttle and then switch to open loop for 3/4-full throttle. It's not really anything to do with acceleration/speeds.
I don't know whether standard Corsa ECU runs closed loop all the way to full throttle. If it does, then it might be worth getting lambda sensor checked (i've had 2 fail on me). Get the plugs checked too for signs of running lean. Doubt it would be worn cams at 70K miles. So many other more highly stressed components to wear first.
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corsa_godfather
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Registered: 6th May 03
Location: Greenock,Scotland
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crank shaft sensor!
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breestyle
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Registered: 2nd Oct 02
Location: banff- aberdeenshire
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cheers for i suggestions lads.
but it was the cam shaft pullys that were warn. he said the ecu stopped comin on a while before this was fixed.
dont think he can afford a new engine greasemonkey but ill put the idea in his head
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ainsley_brader
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Registered: 24th Mar 02
Location: Tattershall, Lincolnshire
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So is it sorted?
If not just find a garage with a hand held scanner (sun/snap-on one will do) and get them to plug it in and take it for a drive.
Read the fault and problem fixed!
Its that simple!
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