Slight misfire when cold on my Caterham 1.8 K series

[zed4]

Hi,

I've not been posting much on here lately, but I've been enjoying the Caterham. It's fantastic fun! I do have one small problem that perhaps you could help with. My 1.8 K series (X-Power model) in my 2004 Caterham Roadsport has a slight misfire when it's cold. Any ideas what could be causing this?

It doesn't idle very well when it's cold and if you try to drive off straight away it can misfire. If you leave it to idle for a few minutes then it's fine. Is this nature of the engine, or a faulty sensor, or...?

The car has only done 19k miles and runs perfectly once it's warmed up a little.

Thanks,

Dan

[DVandrews]

Check the coolant temperature sensor that the ECU uses, this is on the water rail, the one with two connections. The IACV can also cause issues as can the throttle position sensor.

Dave

[zed4]

DVandrews said:

Check the coolant temperature sensor that the ECU uses, this is on the water rail, the one with two connections. The IACV can also cause issues as can the throttle position sensor.

Dave

I removed the intake air temperature sensor and cleaned it, it looked brand new so I put it back. Don't think I've checked the coolant temperature sensor yet. Is the throttle position sensor adjustable, like it is in my TVR (it had a slotted hole). Does it need to be set to a certain voltage?

[DVandrews]

The TPS isn't adjustable per se, although you can reset the ECU so that it relearns the IACV position, turn on the ignition, press the pedal to the floor 5 times in succession, then start the engine.

The corrections for air temperature are minimal compared to the corrections for coolant temperature, I would say the CTS is a prime suspect.

Dave

[zed4]

Hmm, ok I checked the temperature sensor and it seems to be within range. However, one article I read online suggested that when the connector is removed from the sensor the fan should come on. It doesn't. Is that true? The car doesn't seem to run any differently when I disconnect the connector. I might buy a new sensor anyway, seeing as they're cheap.

I've bought a an idle control valve from ebay, it's used but apparently in good working order. It will be interesting to see if it's any different to the old one. I've also ordered a new air filter from Caterham as the old one looks a bit tired.

[tight fart]

Put some new plugs in.

[dptdpt]

and replace the distributor cap

[BertBert]

dptdpt said:

and replace the distributor cap

That'll be a challenge!

[zed4]

BertBert said:

dptdpt said:

and replace the distributor cap

That'll be a challenge!

In other news, I've ordered a replacement idle control valve which should arrive today. I have a feeling that's the culprit. I did pull the plugs out, they were really clean and looked fine. It only happens when it's cold, it's fine when it's warm.

[zed4]

Well I cleaned the butterfly valve, fitted a new air filter, reset the throttle position sensor and cleaned the temperature sensor electrical connections and it all seems fine now. I've used it all week in some pretty cold temperatures and not a sign of hesitation or misfire so that seems to have sorted it.

I didn't get round to changing the idle control valve, seems I don't need to now, so I'll keep it as a spare.

[zed4]

Thought I'd update this thread. After changing the coils, HT leads, plugs and idle control valve, and cleaning everything else, it ran better, but not perfectly. The revs still hunted and it would be very jumpy at low speeds.

We seem to have finally sorted it now though! A local Rover specialist diagnosed the lambda sensor as being at fault. We changed it for a new one and it runs perfectly. Good as new. Really happy with how it drives now.