Cutting out when hot

Technical Area Engine, Transmission, Exhaust etc
1

I’ve just finished a mini resto on a 1991 1.6 Eunos and when the engine gets fairly hot it cuts out and is difficult to restart.
Today it cut out on me and I couldn’t restart it for 5 minutes, I did open the bonnet at this point.
I’m aware it could be either coil pack/cam angle/coolant temp sensor but is there a method for testing to try and narrow it down?
Starts great when cold.
Thanks in advance.

2

Hi Craig

I would discount CAS - cam and crank sensor. I would also think it unlikely to be temp sensor at rear of engine as this usually struggles for a moment between choke and normal running but unless under serious load would not stall the car.
Coilpack is a poss but these are pretty reliable on the 1.6 MK1/Eunos. Having said that I have seen some really dodgy ones recently that allegedly work!, I wouldn’t chance them for a test on my cars.
Have you done an LED diagnostic check?

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3

Not yet, the car cut out on me around 2 miles from home so ive left it there to cool down.
Will get it home later and do the code read.
Luckily my father in law has a 1993 model so could borrow the parts from this.

4

Well why not? someone’s parts and someone else’s advice. It appears to be what is it all about nowadays :slightly_smiling_face: Good luck!!

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5

I wouldn’t discount the engine coolant temperature sensor on the back of the head. I’ve had a case where it was the cause of an engine cutting out when hot. I was fooling the ECU into thinking the engine was still cold so the engine was being over fueled.

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6

So pulling the codes I think I got 26 and 1.
26 makes sense, I’ve got a carbon canister delete.
1 is ignition pulse, I did find the coil pack connector not seated quite properly, it hadn’t clicked the retaining tab so maybe it was this all along.

7

26 is purge valve and one of two that is flagged before ignition; the other being MAF, code ‘8’.
ECU does not monitor coilpacks; ‘1’ is igniter which may well be the issue.
You have the spares available; a very easy swap to test.

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8

Took it for a good run today and got it nice and hot and it didn’t miss a beat so I’m hoping it was a poor connection at the coil pack.
Will keep the spares in the car just in case!

9

Hopefully that is it:-)
The coilpacks are not monitored but perhaps the failure of the igniter to connect with the coil units on your MK1/Eunos 1.6. is?
All other MX5s, MK1 1.8, MK2 and MK2.5 have coil units with built in igniters.

10

I’d guess as it’s not firing correctly it logs the code 1 as it’s not that intelligent a system.