Club G40 Forum

Technical => Engine and Transmission => Topic started by: JoeH on October 05, 2021, 09:16:56 pm

Title: Hesitancy / Misfire 1500rpm-2k COLD only
Post by: JoeH on October 05, 2021, 09:16:56 pm

Hi Guys!

As per title.
Fairly stock G40 which when cold, first 2miles or so, produces a real hesitancy around 1500-2k.
Idle is fine hot or cold.
Higher rpm's seem to sort it - like it's forcing the engine to fix itself.
Warm engine sorts it too.

This leads me to thinking it would be the blue temp sender as that is temp dependant, but it isn't.

To my knowledge spark side is ok: Coil - Cap - Arm - Leads - Plugs

Any help much appreciated.

I have read these two threads which seem similar:
https://www.polog40.co.uk/forum/index.php?topic=13603.0
https://www.polog40.co.uk/forum/index.php?topic=8041.0

Title: Re: Hesitancy / Misfire 1500rpm-2k COLD only
Post by: JoeH on October 16, 2021, 10:14:23 pm

Problem Solved.

I had a dodgy spark plug - see pics.
Which for some reason worked when very cold - choke on.
As soon as auto choke finish car ran on 3 cylinders.
Then when warm it was fine.

Lesson learnt - plugs aren't expected to do north of 20k

Comparing Bosch W4DPO to the new NGK's
(https://i.imgur.com/Jp5uFZV.jpg)

Dodgy plug you can see is really yellow - like it's burnt out...
(https://i.imgur.com/6ihdbAL.jpg)

Replacement NGJ BPR7EIX cost £40quish and work great!
(https://i.imgur.com/1hVPwGZ.jpg)