On literally my first few laps at the Llandow Track Day last weekend, the car felt like it was hesitating a little in fourth gear... I noticed it once or twice, thought it was odd, and then came into the pits thinking it was just me being overly 'sensitive' having not been on track for a few months. After all I'd just driven some two hundred miles to the circuit without a glitch...
...I had a quick chat with Alex Graham, and agreeing it was probably an airflow issue, we decided it best to unplug the Lambda sensor and see what effect that would have.
|I'm not dead - just unplugging the lambda sensor|
Car with stuttering throttle - The accelerator was planted to the floor when the car was stuttering and slowing down in the video below:-
So back into the pits it was, and some more head scratching... The lambda sensor was plugged back in again, and this time a group turned up to lend a hand... We removed the bonnet, started the car and everyone started gently pulling and prodding the visible cables and connections on the loom.
|Plenty of help - pulling and prodding cables and connectors|
|Signs of arcing on the connectors of the airflow sensor connection block|
The next day on the drive home the car started stuttering again, sometimes worse than others, so knowing what the problem was, I drove carefully back. When I got home I took a picture of the sensor and connector block and emailed it to Tony at the Caterham Parts department. He said that the sensor was easy to get hold of, but the connector block was a special order from the company that makes the looms.
|Caterham R500 Airflow Pressure Sensor and Connector Block|
It's a pretty easy fix really (approx 30 minute job), but here are the steps I went through.
First, I removed the connector block - a 'top tip' when working with electrics - take a picture of the wiring BEFORE you take it all apart - it makes things a lot easier when you're putting it back together!
|Picture of wiring of rear of airflow sensor connection block|
Next up, get the connectors out of the block. Seemed a bit fiddly at first, but once you know how to do it, it's dead easy. The white block in the image below is used to lock the connectors into place, and is removable, by pulling forward with a screwdriver. With the lock removed you can then place a small flat-head screwdriver into the connectors and then pull them out, gently, from the reverse.
|Connector 'lock' with visible signs of arcing|
|Connector replaced, all ready for crimping and the refitting.|
|Connector, connection block and airflow sensor replaced - now time to test it!|
As you can see from the video it started and ran perfectly. I took the car for a half hour (or so) blat with Karl who was over from Ireland for the weekend, and no problems surfaced - so with that, it seems like the problem is fixed.