Engine running badly and stalling at idle

[AgingGeek]

Hi all, so I have a problem I am hoping someone can help me diagnose!

I had a problem a while back where sometimes the car would struggle to fuel and could stall, leave the car off for 30 secs and it was fine again for a random amount of time. It was likely due to the amount of rust in the fuel tank occasionally blocking pipes, so I replaced the tank, fuel pump and pressure regulator for new ones, problem solved!

Now another fault has just arrived. It seems the car when hot wants to stall at idle and is puffing black smoke, I have to keep the revs up to stop it from stalling completely. So I assume the car is over fuelling... It doesn't do it when its started from cold, but as the engine gets hot, it just wont idle well at all, it drives OK (ish) but misfires and splitters sometimes, so the car is not being used.

Also, the car is using a lot of fuel, before I noticed the issue, I filled the tank with £85 worth of fuel and emptied it in around 120km, so there is clearly a problem.

Any ideas where to start? It feels like its compensating from lack of air by over fuelling? Hence the black smoke at idle?

Are there any common known issues around this? Somewhere to start? I should mention that the car was running just fine, this has just all of a sudden started to happen and nothing has changed...

 

[Mr Tenno]

What's the current engine setup - still stock 280z?

 

[AgingGeek]

Yup, 100% stock

 

[Farmer42]

Don't know much about 280Z but does it have a cold start sensor like the ZX? If not perhaps some form of automatic choke? sound like it is something like leaving your choke out on a carburettor-fuelled system.

 

[Huw]

Change the water temperate sensor, not the single pin sensor( that’s for the gauge). It has 2 pins and looks like the attached. They are the most common point of failure for 280Z & ZX EFI systems.

OE SPEC Water Temp Temperature Sensor ECU 2 Pin - For Datsun S130 280ZX L28ET | eBay

For Datsun S130 280ZX L28ET. Water Temperature Sensor. Twin Pin Sensor. 12 Valve, Overhead Cam, Inline Six. Two Pin Square Connector.

www.ebay.co.uk

This tells the ECU how hot the engine is and increases or decreases the injector pulse accordingly. So if the sensor is going duff it could be failing high resistance or even open circuit when it gets hot and so the ECU thinks the engine is cold and will wind up the fuel mix making it run hugely rich.

Try changing this component first as it’s an easy fix. If it’s not that then best work through the fault sections of this doc:

 

[AgingGeek]

Change the water temperate sensor, not the single pin sensor( that’s for the gauge). It has 2 pins and looks like the attached. They are the most common point of failure for 280Z & ZX EFI systems.

OE SPEC Water Temp Temperature Sensor ECU 2 Pin - For Datsun S130 280ZX L28ET | eBay

For Datsun S130 280ZX L28ET. Water Temperature Sensor. Twin Pin Sensor. 12 Valve, Overhead Cam, Inline Six. Two Pin Square Connector.

www.ebay.co.uk

This tells the ECU how hot the engine is and increases or decreases the injector pulse accordingly. So if the sensor is going duff it could be failing high resistance or even open circuit when it gets hot and so the ECU thinks the engine is cold and will wind up the fuel mix making it run hugely rich.

Try changing this component first as it’s an easy fix. If it’s not that then best work through the fault sections of this doc:

Thank you!!

 

[AgingGeek]

Thanks all, it was indeed the water temp sensor, all sorted now