I keep busting sensors. Help


I installed the Spartan 2 with the LSU4.9 it came with, connected it to my Speeduino ECU and it works. Great. I blew my first sensor after about a month. It only reads superlean, it worked correct before it broke. My guess; I messed about with the tune getting the car going. The second sensor gave up in similar fashion two months later, the forums and Fakebook told me I should only fire up the Spartan 2 after the engine had started up. OK, so I made a 20 second delay after reaching 500 rpm or more. New sensor, back in business. Third sensor broke a lot later, but the car was off the road for a while for new sills and a respray. Some people say it is from the temp shock because I use fuel cut on decelleration. I doubt that. New sensor in. That one failed me again, now after a few months. The sensor is in the correct position (sensor poining straight down, wires up), just after the final Y junction on my Mazda MX-5 NB 1.8. I doubt the sensors are the problem, as huge numbers of OEM cars run those without issues. I only used genuine Bosch sensors. I now tried an AliEpress sensor, but that didn’t work in the first place. I can buy a Bosch sensor again, but I need to find the issue. Spending € 90,- bi-monthly on the sensors is getting old, not to mention expensive. On Fakebook, I find other users of the Spartan 2 with similar issues, but also happy users. What can I check, how can I prevent the failure of the sensors?


Are you running leaded fuel?

Is the engine turbo or super charged?

Nope, regular ron97 euro unleaded fuel. E10 is the europe wide name. The turbo is still on the workbench, awaiting me getting the Speeduino under control.


Did you install the temperature status LED, it could be that the sensor is installed too far from the exhaust and can not keep the temperature of the sensor at 780C which is used to burn off carbon deposits.

Yeah, I did. Of course it flashes slowly when starting up, but once solid it never goes back to blinking. So my guess is it is in the right temperature range while working. I cannot place the sensor closer to the engine as this is the first place all flows merge, but it is in the same place a lot of other MX-5 drivers have it installed.


Might be asking stupid questions.

But wide band probes in general are susceptible to induction and stray currents.

Is your ground solid? Contamination of your sensor ground could cause weird problems like breaking sensors. I seen it happen on fiats (and alfa’s) due to bad coils in combination with a bad ground. But those have bad coils as a known problem

Also, is there a chance the sensor is contaminated by coolant or overheating?

i seen brand new sensors getting killed over and over again when a multi air engine starts to run lean due to a valve module failure.

not an expert. but i agree that breaking 1 sensor is bad luck, 2 makes you wonder and 3 is a trend that needs close examination.

my gues would be to scope both power supply and ground to rule out stray currents or a bad ground. Dodgy grounds are a hell. And i can know. I work italian cars for a hobby.

Dinand Broekhuis