Vauxhall Cavalier (1988 - 1995) - '89-'941.6 (c16nz) fuel mixture problem! | Technical matters | Back Room Forum

Fri 21 Dec 2007 23:29

'89-'941.6 (c16nz) fuel mixture problem! - xrictodGRE

Hello!
I have a opel vectra 1.6 (c16nz)
The motor warning light is flashing always and the rpm is changing from 500 to 1500 all the time.
Sometimes the engine stops because the rpm is falling under 500 and some others the engine works at 4000 rpm for about 2-3 minutes whithout pushing the throttle pedal.
Some other times i have no throttle.
When i drive the highway the warning light lights and remains on until i stop the engine.
I checked the car and told me that is bad fuel mixture. (the voltage of l-sensor is not varies)
I changed the l-sensor. the same problem
I changed the "cold"-sensor on the uptake (after the injection gas jet). the same problem
I cleaned the injection. The same problem
I changed the ecu and i still have the same problem!
The motor light is still flashing (like a bad electric contact)
what else i must check??
Thank you

Hi I guess you're posting from abroad ! Hope you don't mind but I've filed this under the UK nomenclature of Vauxhall's equivalent Cavalier. Welcome to the BR there is a wealth of knowledge here - frightfully British I know but its no swearing old man !!

Edited by Pugugly {P} on 21/12/2007 at 23:33

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Fri 21 Dec 2007 23:40

'89-'941.6 (c16nz) fuel mixture problem! - Number_Cruncher

What exactly is your fault code? Is the fuel mixture always too rich, or always too weak?

If weak, check for air leaks - including the fuel tank venting system, the pipe to the brake servo, in fact anywhere you would expect to find inlet manifold vacuum. If any air leaks into the inlet manifold, the fuel system can't comensate properly, and you get a light on - you also get rough running if enough air gets in.

Number_Cruncher

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Fri 21 Dec 2007 23:50

'89-'941.6 (c16nz) fuel mixture problem! - Screwloose

To add to that; check the gasket under the injection unit. They often split.

If you have any cracks or leaks in the exhaust manifold, that too can cause a bad fuel mixture reading.

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Sat 22 Dec 2007 10:10

'89-'941.6 (c16nz) fuel mixture problem! - MerlinTec

Hi
I have had the inlet manifold gasket split and give your fault. You can sometimes even see the gasket sticking out.

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Sat 22 Dec 2007 12:13

'89-'941.6 (c16nz) fuel mixture problem! - topbloke

there is also a valve on the bulk-head that is vac operated and these fall apart

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Sat 22 Dec 2007 12:15

'89-'941.6 (c16nz) fuel mixture problem! - topbloke

you should be able to get the blink codes out of the ecu for this model

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Sat 22 Dec 2007 13:21

'89-'941.6 (c16nz) fuel mixture problem! - Dynamic Dave

you should be able to get the blink codes out of the ecu for this model

Details here:-

www.topbuzz.co.uk/info/fault_codes/fault_codes.htm

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Sat 29 Dec 2007 18:05

'89-'941.6 (c16nz) fuel mixture problem! - xrictodGRE

ok
i get the code. its code 51
Defective ECU (disconnect and reconnect (ECU), then recheck for fault codes). Memory failure
I reconnect the ecu many times but the problem exist.
I discovered that when the engine was still hot and i tried to get the codes always i had the problem that the light was flashing simultaneously with the flashing through the test and i couldnt realized which is from the problem and which flash is from the test.
i test my ecu with the engine cold without problem.
My previous ecu gives a code 45 Oxygen sensor Air/Fuel mixture too rich (i knew it thats why i replaced it) but the symptoms are the same
maybe i have to replace again my ecu with a third one.
what do you think?

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Sat 29 Dec 2007 18:41

'89-'941.6 (c16nz) fuel mixture problem! - Screwloose

Refit your original ECU - there's nothing wrong with it and code 51 is for incorrect programming on this one. [Wrong ECU.]

You got code 45 because the mixture is indeed too rich at the oxy sensor - don't shoot the messenger - it's just telling you what's going on.

Check the MAP sensor's output voltage and the hose to it for blockage and leaks.

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Sat 29 Dec 2007 19:47

'89-'941.6 (c16nz) fuel mixture problem! - xrictodGRE

oh my friend thank you 4 your help but can you be more specific about which part is the map sensor?
so you telling me if i am right that the one with the code 45 has a problem with the map sensor and the other with the code 51 has a bad programming?
im sorry but i didnt understand

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Sat 29 Dec 2007 20:24

'89-'941.6 (c16nz) fuel mixture problem! - Screwloose

Not quite. If you get code 51 from the replacement ECU, then it's likely saying that it's not the right one.

On your original ECU; you got code 45 telling you that the oxy sensor wasn't switching because the mixture was too rich - nothing was wrong with either the ECU or the oxy sensor, they were just alerting you to the fact that the mixture was too rich.

Finding out the reason for the mixture being too rich is the task that you now need to address.

One of the main mixture control sensors is the MAP sensor on the bulkhead - check it's hose and it's voltage output to the ECU carefully to find out if they are correct. If they are, you'll need to look elsewhere.

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