I have 94 1.8i Roadster Eunos. Whilst driving, the heat light shows up on the warning light panel on the dashboard (next to handbrake, seatbelts and battery charge lights). It starts fine from cold, but once the engine is warm it misfires and dies and will not start until it cools down. Is the light pointing to the heat sensor being faulty as the temperature gauge shows normal temperature.? Any advice would be appreciated. Thanks.
The misfire is the real fault; the Heat light is just a symptom of the misfire. The misfire will almost certainly be caused by a failing sparkplug lead - easy to change, and a new set’s not very expensive. The Heat light comes on when a sensor at the back of the catalytic converter overheats - usually because a misfire lets unburnt fuel reach the cat converter. This sensor is only fitted to Roadsters, not UK cars, and it only lights the lamp in the dash, it doesn’t alert the ECU or affect any other system in the car. There’s some debate as to whether the lamp should be self-cancelling, but for most folk the first they know of it is when the sensor fails and the lamp comes on permanently. Nobody bothers to replace the failed sensor (they’re not available in the UK anyway) so we just unplug them and tape the cable up out of the way or just snip it off. (there’s a plug in the cable within a foot of the catalytic converter). Disconnecting it puts the light out permanently.
Hi, thanks for the reply so soon. I have only just bought the car, I managed to get it home from 40 minutes away without a problem, and then as heat light has appeared it has been miss firing after 15-20 minutes driving, never at first.
It looks like the leads are new, but I will have to get some more and then see what happens.
I am slightly confused however as I bought a sensor-temperature engine coolant, for the 1.8 from mx5parts. Is that only for UK cars not the imported Eunos Roadstar, or is this something totally different
I bought the sensor after looking at previous posts on the old forum, where they described the exact problem in detail including the revs going mad, and they spoke about changing the sensor or coil pack, but didnt however mention anything about the heat light.
Is the heat sensor to do with the catalytic convertor or the temperature of the engine coolant?
sorry for all the questions and thanks again
It refers to the cat, not coolant temp.
Check leads & plugs - could be loose or worn out. (Old leads will look new if sprayed, and they don’t last long on the 5).
While you’re there, remove plugs - clean, check gap, re-fit (or maybe just replace them…).
Air filter is cheap & quick to replace.
Then see if problem still exists.
Thanks for clearing up that point, I will check the plugs and leads tomorrow and change them if in doubt.
Fingers crossed!!
Thanks, Jess