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post #9 of (permalink) Old 19th February 2008
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Hi All

I've had this exact same problem for some months now.

To clarify, it occurs on starting, the "injection fault" light comes on (during dashboard light test, but fails to go out) and then once you press start the revs jump to about 2000 and sit there. There's a rapid "pulsing" effects too, as if you were pumping the throttle peddle, or one cylinder was not igniting.

The throttle is completely unresponsive and you have no control over the engine.

You can drive the car (slowly) and the engine seems to respond to load by increasing the throttle position (you notice this when you press the clutch down as the revs jump up to 3000ish and are erratic).

The fault has never happened with the engine running, only when starting.
The fault has never stopped whilst the engine is running, only after switching off and re-trying.

The "fix" is simply to wait about 10-20 minutes and try again.

It seems much more likely to happen when the engine is hot.
I don't think this has ever happened when the engine is cold. I usually get it after the engine has been running a lot (long drive or sitting idling for ages) and I stop and restart (stop at a shop or petrol station etc.) quickly.

More likely when it's warm outside, has only happened once this winter (after a long period of idling).

I think it's related to some other weird problems I'm having.
The " oil ok" message is random. Sometimes it appears, other times it goes straight to the milage display!
The air temp display is almost always not there. The times it is there it is either about right, or it is 50 degrees! (or just slowly counting up or down between then two numbers!)

My OBD2/CAN reader shows the IAT (Inlet Air Temperature) as stupid numbers like 55 degrees.

The climate control doesn't function correctly using "auto", it doesn't output the required amount of heat according to the temperature specified. The only way to get heat is to use 26 degrees on manual.

The wiring in the engine bay was distrubed (I took the engine out and rebuilt it completely), but I've checked it and it all seems fine with no (external) damage. I wonder if one of the wires inside has broken (when the cable was bent in a different way).

The engine is running rich, and the mpg is down from where it should be. Spark plugs are coming out blackened from too much fuel.

Some missfiring at low revs under load (and occasional pop from the exhaust manifold as the unburnt gas explodes in the manifold).

I've also noticed odd things with the ABS brakes. They seem to work fine most times, but they have definitely failed a few times causing a front wheel to lock and remain locked.

I realise that most of the faults listed above seem to point towards the air temp sensor being at fault, but there are other issues that have nothing to do with that (and they all started at the same time, after the engine was put back into the car, and the battery reconnected after a period of being disconnected). The " oil ok" is a good example, this has nothing at all to do with air temperaure!

Any ideas or advice greatfully accepted.

Does anyone know a good way to test the air temp sensor (normal impedance values etc)?
Does anyone know if there are TWO sensors? One for "outside temperature" (mounted in the bottom of the drivers mirror enclosure), and another for "inlet air temp", mounted in the air intake path presumably??

Currently in jbinks's garage:
2002 Renault Laguna II 1.8 16v Expression
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