420R Running rough

[KnifeySpoony]

I had a high rpm, high load misfire caused by wire failure in the coil subloom to coil #1. My theory is that the coil cover puts stress on that wire leading to failure. I think that's why cc puts that hole there, with grommet to try to give more relief for the wire, but there solution is poor. I removed the grommet, which gives additional space for the wire to have a more gently curve. I repaired the broken wire and bought a backup subloom to have to quickly swap out if necessary. 

[John Vine]

#26  I'm not sure I understand that.  The hole is at the rear of the coil cover, next to cyl #4 not #1.

JV 

[Tony Leigh]

Apologies for not giving an earlier update, but the problem with my car turned out to be the ECU.
 

I did a bit more investigation myself in late November and using a NOID light diagnosed the problem to be no signal to no.1 coil pack. As others had mentioned that the wires in the connector to no.1 coil pack sometimes fail due to vibration I purchased a new engine sub-loom. When it arrived I eagerly fitted it expecting my misfire to be cured. Alas this was not the case. At this point I decided to hand my car over to an expert, so I contacted Luke Stevens (Team Leos). I wasn't in any great hurry as I don't use my car in winter, so it wasn't until a couple of weeks ago that Luke took my car. I spoke to Luke this week and he said that there is a fault with the ECU, most likely the driver for no.1 cylinder. He has seen this before but it is fairly unusual. 

He has also found that the Lambda sensor has failed along with the alternator, and the battery isn't in great shape either, so quite an expensive week. I knew the battery was starting to struggle so that wasn't a huge surprise. It is possible that the Lambda sensor failure was exacerbated by running the car with a misfire (I had no choice but to drive it home following the failure but my subsequent 'testing' when trying to find the problem may not have helped). The alternator is a part failure, it only charges at high revs and doesn't charge at low revs (<2000). Luke tells me that this is often as a result of vibration from the Duratec causing some of the windings to break.

I haven't picked my car up yet, and I haven't asked how you can specifically diagnose the ECU fault as opposed to the other possible issues but I imagine this involves interrogating the ECU which I don't have the connector or software for.

In the process I did learn about NOID lights which are 12v lights that you can connect in to the engine sub-loom connectors and see whether there is a pulse to the coil packs or injectors.

I'm not sure how much this helps others (MTW) but that is the position with my car. 
 

All part of the 'fun' of owning a Caterham, I guess.

 

[KnifeySpoony]

#27.  Woops yep other end of motor! 

[Jonathan Kay]

Thanks for adding the answer.

"I did a bit more investigation myself in late November and using a NOID light diagnosed the problem to be no signal to no.1 coil pack."

Just the sort of occasionally needed kit that's so valuable in the Equipment Register...

Jonathan

[Jonathan Kay]

"He has also found that the Lambda sensor has failed along with the alternator, and the battery isn't in great shape either, so quite an expensive week. I knew the battery was starting to struggle so that wasn't a huge surprise. It is possible that the Lambda sensor failure was exacerbated by running the car with a misfire (I had no choice but to drive it home following the failure but my subsequent 'testing' when trying to find the problem may not have helped). The alternator is a part failure, it only charges at high revs and doesn't charge at low revs (<2000). Luke tells me that this is often as a result of vibration from the Duratec causing some of the windings to break."

Even without dedicated test kit it's possible to get a quick look at the condition of the battery and the operation of the charging system. I usually recommend 3,000 rpm for the latter but that might have missed this one.

Had you noticed any change in when the warning light came on?

Thanks

Jonathan

[John Vine]

#28:   Thanks for the update. 

(My sympathies over the bill...)

JV

[Tony Leigh]

Reply to #31

Jonathan,

I hadn't noticed the warning light coming on. When the car is not in use I use my battery isolator and over long periods put the battery on a trickle charger. I noticed that it was a bit more laboured when starting the engine but no other issues and just assumed it was an age issue (the battery is 3.5 yrs old).

[Jonathan Kay]

Thanks

Jonathan

[Geoff Brown]

Failure of the ECU #1 coil pack driver has occurred in brand new cars as well. 

Obviously a weakness of the ECU internals?

[John Vine]

This is very interesting. 

Can persistent misfiring cause driver failure?  In my own case (2008 R400D with coil-on-plug ignition), I suffered for some time from the well-known problem of vibration-induced coil-loom failure -- specifically, a fracture in the #1 lead.  I fitted CC's beefed-up race sub-loom, and that fixed the fracture problem.  Some time later, I suffered total coil failure on #1.  I'm surmising that there may be a link between the two events.  To date, I've not experienced any ECU driver problems, but I'm left wondering whether they could be lurking behind the scenes, waiting to bite?

JV  

[MTW]

Thanks for the info!