Poorly Perodua - Persistent Problem (Help?!)

[TonyMac]

I've got a '99 Perodua Nippa that was bought as a temporary car while I MOTd my other one. It's on a Boris MOT and probably should be scrapped but unfortunately I've grown quite attached to the horrid little shonkbox.

Anyway, from a cold engine it fires up lovely but if run until it gets warm and then switched off it either doesn't start again or starts eventually but bogs down and misfires (fires badly on 3 rather than not firing on any of the 3 individually). Worse under acceleration than anything else. No EML light on (annoyingly it isn't OBD 2 so can't check for codes).

Any ideas? Parts are a total nightmare to come by so diagnosing the problem is only a small part of the battle.

[GreenV8S]

At that age I assume it has lambda sensors. If the O2 feedback system is working properly, you should see the output voltage from each lambda sensor cycling cleanly between rich and lean every second or so (faster is better). See what it does when the problem occurs. It may be the lambda sensors aren't being heated (or not enough) and they aren't working after the hot start.

You could also use a passive strobe to check the spark strength and a NOID lamp to test the injection pulse width to see whether the misfire can be traced to a weak spark or incorrect fueling. You'd want to compare before and after the hot start to see why it is misbehaving.

[nsa]

The Porsche 924 has a cold start valve that fails and causes the same issue you have. Might be worth checking if your Nippa has one:

https://www.google.com/search?q=porsche+924+cold+s...