K series EU2 1.8 Missfire under load

[Dixa1225]

I have K series EU2 1.8 . I am getting a misfire under load . This can happen either hot or cold . Annoyingly this is intermittent ! Any ideas ? plugs , cap & rotor have been replaced 300 miles ago . HT Leads the next to try ? 

[Jonathan Kay]

Has it been out in the wet recently?

Jonathan

[Dixa1225]

Nope , nor been washed

[Ivaan]

Have a look in the dark/ Any electric leaking out anywhere? ( or grab hold of the HT leads whilst the engine's running          )

[Markiebabes]

Have you tried the TPS ? 

 

[Graham King]

I'd second Mark's suggestion, the symptoms you describe, whilst could be attributable to a number of things are exactly what happens when the TPS (Throttle Position Sensor) fails.  

It's an easy fix, unfortunately the TPS isn't the cheapest item in the world. 

Graham.

[Dixa1225]

Thanks for the suggestions , I am going to replace the leads & I do have a spare Throttle Position Sensor so will replace that to.

 

[Mr Locust]

Ensure that the centre HT lead hasn't been re-routed next to the crankshaft sensor at the rear of the engine otherwise interference can cause strange effects.

[Piers300]

Would the HT lead being near the crankshaft sensor cause the engine to not start or fire on any cylinder ?

Because I have a problem with my R300K sometimes it just won't start. If you mess with the HT leads, it will sometimes start

 

Piers

 

[Mr Locust]

The case I saw was on a friend's VHPD engined SLR.  In that instance the car was fine under high load but idling and light/low speed running were really poor.  When we moved the coil lead away from the crank sensor the issue went away.

If there was a significant interference issue with the crank sensor it could affect starting.

[Bottrill]

Check the coil HT lead is seated properly on the new dizzy cap. Before you do this however, spread the inner contact outwards on the end of the HT lead, give the dizzy cap a very light sanding to rough the surface and then replace. Had to do the same on my new dizzy cap/leads as the lead would just slide off slightly causing your symptoms. 

You can test your TPS prior to replacement using this simple technique. Ignore the values given but the theory is simple enough. You are looking for a smooth change throughout the range as you go from base to maximum voltage by slowly pressing the accelerator pedal or opening the throttle body by hand.

http://www.enduringautomotive.com/tps/

 

Lee

[Piers300]

Thank you Lee. This saga has been going on since the 2015 Isle of Wight Blat and I will do as you say over the weekend. There is a post I put on on Technical about poor starting on my R300.

 

Thanks

 

Piers

 

 

 

[Dixa1225]

Hi All,

Just to update this post , replaced leads & TPS and problem still remains*grumpy* . Its very intermitted with some days the car running fine ! Any further suggestions welcome.