If the engine light for my st170 is on caused either by the imrc or lambda sensor fault will it cause any damage if I keep running the car? What would these faults actully'mean' for performance/fuel consumption etc?

 

Or if no one knows the answe, has anyone ran theirs for a while without any (further) problems?

 

It's going to depend on what has caused the light to come on. It could be something as straightforward as an EGR valve sticking or a momentary rich condition which wouldn't cause much of an issue. It could be something more serious resulting in the engine running in LOS, limp mode. This would result in poor performance and terrible economy. Best to get the fault codes read to find out what's wrong. It will fail the MOT with the light on so it'll need fixing before the MOT is due. You can pick up a half decent code reader on ebay for about £20 so it may be worthwhile getting one and reading the codes and resetting the light yourself.

 

It's the orange warning light that comes on. It doesn't seem to affect the running of the car and it's doing an average 31ish mpg. The light goes our for 300 miles after the battery is disconnected but then comes back. It also sounds as if there is a slight rattle on the exhaust. I'll get it checked out next time the light comes on just to be safe.

 

If it takes several hundred miles before the light is back on, I suspect a defective catalyst.
Get the codes read, then we have to stop guessing.

 

It's been a 3 weeks since I disconnected the battery and approx 1000 miles and it hasn't come back on yet. I can't believe I'm almost wanting the light to come back on so I can find out what it is!

 

After staying off for over a month the light came back on and then kept coming back on despite me disconnecting the battery.

Took it for a diagnostic and it's the dreaded IMRC. How much damage will it do if I drive it like this for a few months? Xmas is coming and the expense of that means I'd rather leave it for a while.

Also, would it fail an MOT for something like this?

 

EML light on will fail the MOT.

 

Would it damage the engine as well or just affect fuel consumption/performance?

 

It wont damage the engine. A lad at my work has a ST170 and has been driving round for months with his engine light on. When you turn the ignition lights on the imrc will pull on the cable and open the flap in the inlet manifold.

 

At least I can take my time waiting for a decent one to come up for sale rather than paying crazy money.