KnifeySpoony

Fwiw here in the states, center caps are generally advised to be removed before trackdays. They tend to not last long. I just leave them out on my cars. More rccr than way... 

I am going on the wiring diagram in the back of the 2015 build guide which AFAIK is the most current published? My 420R is a 2021 build btw. 

Ah ok i figured it was something like that given the consistent, but higher residence. What is the mfu? 

I unplugged the coil loom plug at the Coil itself, then tested from the ground pin on the loom plug to the main chassis ground by the battery. For the other pin on the coil loom plug, I unplugged the ECU and tested at the appropriate ECU pin.

FYI resistance was check with ECU plugged in, kill switch on, but car's ignition/power off. 

So I'm still trying to diagnose my part throttle misfire on my 420R. I went and checked continuity on various things - coils, injectors, sensors, etc. Using the continuity check on my multimeter everything was ok with a BEEP. However I realized that it will beep with anything less than 120ohms. So looking at the actual resistance, I noticed that all of the coil (and I think injector) grounds are consistent at 44ohms. Is this normal?

What are the characteristics of the misfire? I'm curious, as I'm diagnosing one as well. 

On the modern dry sumped cars, with the oil tank up front, apparently an inline thermostat only gets you a few degrees warmer. Blocking the cooler will likely be more effective. 

I do have the easimap setup. I will try to decipher the lambda readings. Also i need to confirm 100% that it's a misfire on #4. I will run it then pull the plugs hot to see if #4 is wet. If it is a misfire only on one cylinder, that would seem to eliminate a sensor issue i would think. And tonight i have just checked my wiring continuity on the #4 coil and injector, as well as lambda and MAP sensors. So if #4 is really misfiring then perhaps the ECU coil driver could indeed be the culprit. All this is new to me. Fun times. 

In my mind, it would be odd if it was a connector or some other wiring fault to the coil, as I had exactly that issue last year, which created the exact opposite symptom from what I am having now- ie the car was fine at part throttle and low RPM/load, but then misfired only at WOT at high RPM. My first order of business is to check wire continuity from the coil to the ECU. Will also check for the 02 sensor, as the behavior seems to fit with a toggle between open loop/closed loop operation to me. Another thing that I am considering is the MAP sensor - I have seen threads saying failure there could cause similar issues, but I'm not sure. In the RBTB setup, it's just acting as a temp/barometric pressure sensor. 

Did a trackday at Laguna yesterday - Once again the car was fine on track (new PR actually), however the part throttle issues have deteriorated significantly. It's extremely unpleasant/challenging to drive on the street at this point. It does it even when cold, and doesn't like to rev at all on light throttle in neutral; sputters and coughs bad. I checked the plugs again - they all look fine and all look the same- don't see anything obviously wet - does this mean it's NOT a misfire then? The most rearward cylinder exhaust primary is a little cooler than the other 3 but not cold. While idling (which is smooth, btw), I unplugged each coil plug one by one: the front three cylinders this produces an immediately rougher idle. Unplugging the rear cylinder created no change in idle, however revving is even worse. I swapped coil harness and no change. Swapped coils between 2 cylinders - same behavior. The picture is confusing me more and more... One thing that I noticed is that immediately coming off track with the car very hot, it runs fine around the paddock - However in stop and go traffic on the way home with equivalent water and oil temps, the car was almost undriveable. 

Any thoughts?

I would never drive with an unpadded [full] cage, especially sans helmet. I see it around though. Pad it and run it that way all the time imo. 

What's a wear bar lol? Run em till the cords are showing. That's how we do it in California. No pesky rain to deal with though...

I just use 4 little squares (maybe 2cm at each corner) and it's plenty strong.

Your car already has the 8%. The 8% rack has been standard for some time. I have no experience with the 22%, but even in hairpins I don't have to shuffle with the 8% rack so I've no desire to upgrade. Also effort is already pretty high when under load. 

 I tried unplugging the new sensor and the car runs exactly the same. So clearly my new 02 sensor is not doing anything. So it seems to me that either it's 1: sensor is DOA, 2: it's incompatible (it's a Bosch sensor that used to be included with r400/420R not the no-name sensor my kit came with), 3: the wiring from the sensor to the ECU has gone bad, or 4: the ECU has gone bad. 

Seems like sensor logging wouldn't be that valuable at this point. I suppose I should check wiring continuity; how to do this? Multimeter at sensor plug and at ECU plug? What pins go where? I could also put the OEM sensor back in and see if the behavior reverts or stays the same.

Not to soapbox you, but imo rotor and pad inspection should be done before every trackday, and sometimes even multiple times during a trackday, depending on the car and condition of said consumables in the morning. 

Glad you caught this before something bad happened. 

Well..  It's kinda solved but now there's a new symptom. Now the 5-20% throttle range is smooth, but from 0-3%, ie initial tip-in there is hesitation/sputtering/misfire. And it does it immediately after starting even when cold. Car starts instantly and idles fine. Giving it verrry slight throttle will cause it to sputter/miss. More throttle and it revs fine. Interesting the drastic change in behavior with the new 02 sensor but not sure how to interpret. I'm thinking the 02 sensor isn't even active when the car is freshly started so I don't understand why the new sensor would cause this behavior. I'm going to triple check the TPS voltage, roller idle spacing, sparkplugs, etc.

New lambda sensor and problem seems to be solved. I had the no name sensor that others have mentioned recently. Replaced with proper Bosch part. 

I put in a Spa designs dual temp gauge. Love it.

Can you describe the issue with each gauge in more detail? As others have said, the fixes may be easy. My 420 tach read low when i built it. The dipswitches were set wrong. Even caterham denies the existence of the switches however... 

Given the concern that all Avons will be unavailable soon, I assume many of us will be making this change. To anyone that has actually done it- Did you notice any change in balance going to the narrower rear tire? Where does the Toyo grip fall relative to the ZZS and ZZR? And did you make any ride height /geo changes to compensate for taller sidewalls?

Given the concern that all Avons will be unavailable soon, I assume many of us will be making this change. To anyone that has actually done it- Did you notice any change in balance going to the narrower rear tire? Where does the Toyo grip fall relative to the ZZS and ZZR? And did you make any ride height /geo changes to compensate for taller sidewalls?

Define "performance"

Yes mine moves too. Have you seen how much the dedion deflects laterally under load? Maybe it's by design. Although not many things in our cars are...