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Discussion Starter #1
Hy!

First sorry for my bad english.

So I need to help.

My Cavalier/Vectra (C20NE, Motronic 1.5) has idle problem.
When the engine is cold it's good, when the engine is warm it's good, but when the engine is warm and is stopped the engine and I wait few min, I can't start the engine on first or it's start but ( it has low idle) harder than the engine is cold. But I give it a little acceleration it will be good. (Usually)

I tried with new and used AFM, new and used ICV, new and used water temperature sensor and used crankshaft position sensor.( We have Omega A C20NE without this problem and I tried with Omega's parts on Cavalier/Vectra)

My friends have this problem too, and I know people how has too, and nobody knows what can we do with this...

I hope it was understandable!

Thanks for help!

I'm waiting for your reply!
 

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Instead of playing parts darts get a code reader to see what codes are stored in the ecu. This will point you in the right direction
 

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Over 17 years since I had a C20NE but a dim and distant memory is the EGR valve causing similar issues. Other causes could be an induction air leak, TPS fault CTS wire connector corroded.

The Ecu uses preset values when the car is cold, so issues only show when the CTS reports that the engine is warm. The spade terminal can get corroded and I had 2 CTS fail when they got hot with water leaking onto the contact. Both caused non-start problems when the engine was hot.
 

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Discussion Starter #5
Over 17 years since I had a C20NE but a dim and distant memory is the EGR valve causing similar issues. Other causes could be an induction air leak, TPS fault CTS wire connector corroded.

The Ecu uses preset values when the car is cold, so issues only show when the CTS reports that the engine is warm. The spade terminal can get corroded and I had 2 CTS fail when they got hot with water leaking onto the contact. Both caused non-start problems when the engine was hot.
Hy! C20NE doesn’t have EGR valve.
My TPS sensor is new, so I mean it’s good.
My CTS sensor (If it is the water temperature sensor) is changed for a new.
 

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Have you tried a hot start with the CTS unplugged? Or with another sensor plugged into the connector whilst at ambient temperature. Looking at the lower learned throttle position might hold a few clues too.
 

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Discussion Starter #7
Have you tried a hot start with the CTS unplugged? Or with another sensor plugged into the connector whilst at ambient temperature. Looking at the lower learned throttle position might hold a few clues too.
Not yet, when I will have free time I will try unplug.
I have another sensor and I tried with.
What do you mean in your last sentence?
 

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If you look in the ECU module, you'll see feedback and position sensor data for the throttle body. The ECU will have a learned lower throttle plate position for varying engine temperature. If you can see what the throttle plate is being commanded by the ECU to do, this might give you a better grasp of what's going on during the the warm up cycle.
 

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Discussion Starter #9
If you look in the ECU module, you'll see feedback and position sensor data for the throttle body. The ECU will have a learned lower throttle plate position for varying engine temperature. If you can see what the throttle plate is being commanded by the ECU to do, this might give you a better grasp of what's going on during the the warm up cycle.
What can I do read the ECU module and the live data with? It’s too old for OBD. And I think the MIL Lamp flashes can’t do that.
 

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I'd still suspect the IACV, they were notorious for sticking! However, assuming that plugs etc are clean, the engine in good mechanical order and the sensors that you have substituted are good, then I'd start by checking that all inlet air pipes and breather/vacuum pipes are secure/not split.

Is the fuel pump delivery sufficient? Fuel Pressure Regulator?
 

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Discussion Starter #12
I'd still suspect the IACV, they were notorious for sticking! However, assuming that plugs etc are clean, the engine in good mechanical order and the sensors that you have substituted are good, then I'd start by checking that all inlet air pipes and breather/vacuum pipes are secure/not split.

Is the fuel pump delivery sufficient? Fuel Pressure Regulator?
The IACV sure good, maybe sensors too.
The mechanical is good, before I renew/repair the cylinder head new inlet and exhaust valve.
Vacuum pipes is good.. I checked too many..
The fuel pressure ok, and the delivery sufficient.
Omm.. Maybe everything is okay, but not everything is okay ?
 

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Clutching at straws now! Have you checked compression over all 4 cylinders? Although any small leaks usually seal up when hot and cause misfire when cold. I'm assuming no coolant loss? Last idea.....perhaps nonsense but how about the Oil separator in the camshaft top cover? I assume that you cleaned it all out when you did the head gasket job. It doesn't normally cause anything more than a slightly lumpy idle though.
 

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Clutching at straws now! Have you checked compression over all 4 cylinders? Although any small leaks usually seal up when hot and cause misfire when cold. I'm assuming no coolant loss? Last idea.....perhaps nonsense but how about the Oil separator in the camshaft top cover? I assume that you cleaned it all out when you did the head gasket job. It doesn't normally cause anything more than a slightly lumpy idle though.
Everything is okay.. Compression is good when the engine cold and warm. No leaks and I repair full the cilynder head and change the all covers.
 
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