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Discussion Starter · #1 ·
Tried this thread a week or so ago but it got buried within a couple of hours.

Here goes. 1998 VVC Coupe, 64k, new head gasket this time last year but then didn't move for months (I think the owner knew it needed more work and couldn't be bothered).

The car starts okay from cold - catches at 1200 then a valve kicks in and it goes to 1500. When up to temp it settles at about 1100. When hot though it really struggles to fire. It turns over okay but just won't catch. So far I've replaced the leads, coil pack and cam sensor but no change. I've cleaned out the idle control valve and checked all of the pipe work which seem sound.

I've had various suggestions. "VVC Mech", "Sticking valve", "Lambda sensor", "Fuel pump". I suspect that the engine was thrown back together after the gasket failure without much thought to other possible failures as a result.

Is this tied in with the high idle? Is the engine flooding as a result? MPG seems fine at about 35 (I have a feather foot). Any further suggestions with remedies most welcome.
 

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Discussion Starter · #2 ·
Come on guys, somebody must have some ideas surely!

Forgot to mention, also replaced the plugs.

What about the throttle body, could that be faulty or just need a good clean out?
 

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Discussion Starter · #5 ·
Cheers for that iunfo.

How does a faulty coolant temp sensor affect the hot starting? Is is something to do with the signals it sends back to the ECU? Could it have been knackered when the gasket went.
 

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never come accross this problem before but it sounds like too little fuel is going in, once the warm up enrichment turns off the engine simply is not getting enough fuel to run perfectly.
this may be becuase the engine is running closed loop lambda (it learns from the sensors) when warm, whereas during warm up enrichment it is running open loop which means it is running set values of fuel which are not influenced by the lambda sensor. Which would explain why its running ok during warm up..but poorly when off the lambda sensor in closed loop.

i dont know enough about the ECU to give a better answer i can only give suggestions from running programably ECU's. The ECU u have may not even use Closed loop, im sure a guru will know.

try swapping lambda sensor with a freind to see if it fixes it...

this is just a stab in the dark..


Rich
 

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basically it helps the ecu determine how much fuel to inject, but if its dead the ecu will inject too much/too little and the car will fail to start

andy
 

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coolant sensor -


The ECU uses the coolant sensor to know weahtere the engine is warm or not, if below a certain value (~75°C) then the ECU will add extra fuel into the engine to help it run when cold, this is becuase combustion is not a good when the engine is cold and it will likely stall without the extra fuel. Once the sensor reads over 75 the enrichment map will be turned off.

In the old days every1 used to pull the choke lever out on their dash board to add in extra fuel when the engine was warming up. with the coolant sensor and ECU this is all done for you..

The guys on ebay selling these resistors which connect into the plug on the coolant sensor fool the ECU into thinking the engine is cold there for the ecu adds extra fuel in giving you a tiny increase in power and a big reduction in fuel economy

Rich
 

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Discussion Starter · #9 ·
Thanks guys. Just a point I have picked up from reading through Archive posts. If the Coolant Temp Sensor is shot wouldn't the fan be on permanently? The fan kicks in if I unplug the connector but then goes off again when I reconnect it.

Riko - Where can I find the Lambda sensor? There seems to be hundreds of multi-plugs tucked away all over the place.
 
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