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[mega3.0v6]

Had car plugged into a snap on machine scrolling down the mechanic notice my car was running LEAN/RICH could this be my problem i changed fuel filter yesterday aswell. As i looked underneath and looked like it had the original filter on it as it was a GM one and was rusty so any ideas Please.  

[hotel21]

I'm confused....

Was it lean or was it rich?  Cannot see how it can be both at the same time....   :-/

[Kevin Wood]

Lean or Rich would have been the live data indication from the Lambda sensors. They are supposed to cycle between lean and rich a couple of times per second. The operator clearly didn't know what he was doing, IMO. Sounds perfectly normal to me, unless they weren't cycling. :-/

What is the problem you are having?

Were there any trouble codes stored int he ECU?

Kevin

[mega3.0v6]

The problem i have is that when cold driving the car till it starts to get warm is fine. BUT when it is warm on the 90 degree line between 1k to 2k revs it hesitates when revs get passed 2k all is fine. Had it on tech2 and a snap on machine no fault codes stored or found i have changed plug and leads also oil oil filter (i know nothing to do with it) fuel filter. The vauxhall guy i had look at it quickly said the eml has to be on for the tech2 to find anything. I got a feeling crankshaft sensor maybe when the revs are low that is when it is at fault. but surely eml should come on if there is a fault i have run out of ideas and near enough skint to think of anything else it can be. The car has done 76k on 98 S 3000cc.

[Mike Collins]

Is the ECU getting a sensible reading from the coolant temperature sensor?

It uses a different sensor to the panel display, so a correct gauge reading could be misleading.

If it thinks your engine is still cold it supply excess fuel, that won't help the way it runs.

One of the live data displays is coolant temperature, at least on the Opelscan.

[mega3.0v6]

Could this go if the oil cooler had gone. How can i find out if that is working or not working properly.

[Mike Collins]

Simplest way is to plug in a diagnostic device that will display temperature and voltage from that sensor.

You could measure its resistance hot and cold, I don't know what values to expect, at least they should be different.

Oily residue might have contaminated it, anyone seen that?

[mega3.0v6]

Is there a switch on the gearbox (manual) as i heard a load click when changing gear and when it starts to do the jurking i dipped the clutch and it revved up fine.

[Kevin Wood]

The problem i have is that when cold driving the car till it starts to get warm is fine. BUT when it is warm on the 90 degree line between 1k to 2k revs it hesitates when revs get passed 2k all is fine. Had it on tech2 and a snap on machine no fault codes stored or found i have changed plug and leads also oil oil filter (i know nothing to do with it) fuel filter. The vauxhall guy i had look at it quickly said the eml has to be on for the tech2 to find anything. I got a feeling crankshaft sensor maybe when the revs are low that is when it is at fault. but surely eml should come on if there is a fault i have run out of ideas and near enough skint to think of anything else it can be. The car has done 76k on 98 S 3000cc.

He clearly doesn't know how to get the most from his diagnostic equipment!  

Some faults don't light the EML but are stored anyway. In addition, problems like this can be diagnosed by watching how the live data behaves when running, if you have the knowledge to interpret it.

I say it could be a crank sensor (which would normally generate a code but NOT light the engine light), temperature sensor, as mentioned or a problem with a lambda sensor, as these are normally disabled at low coolant temperatures.

A look for fault codes, and the live data, would confirm the problem, I'm sure. Shame the guy with the Tech 2 was not a bit more switched-on. You can spend thousands on diagnotic tools, but if the user is a muppet....

Kevin

[mega3.0v6]

LOL i agree. Would doing a paper clip test tell me anything.

[albitz]

it would give you any stored fault codes,crank sensor would be code 19.

[Mike Collins]

It won't help you with temperature sensors.

[mega3.0v6]

Where will i find the temp sensor not the one for the dash gauge but for the ecu is it next to the dash sensor one. :-/

[Mike Collins]

They are both screwed into the coolant bridge, if I remember, one has more terminals, but I can't remember which is which.

[Kevin Wood]

The one with just a single terminal is for the gauge.

Kevin