I happened to be negligent enough to leave the air filter unchanged in my Hilux KUN26, engine 1KDFTV — for 5.5 years and 47k kms (30k miles).
The vehicle was seemingly all fine until one day I started it cold, drove it out of my gate, went out to close it and heard the engine stall while idling. "Wow" I thought. "What the hell was that?"
So I started tests: engine would consistently stall (if idling) after about 0.5-2 minutes after start. If accelerated, it would go fine. But when put back to idle, it would stall again pretty soon.
A quick search identified potential causes, and I went to check the air filter. Jeez! So, I got a new one. Here they compare:
So I replaced the air filter and started testing again.
- 1st attempt — same as before. I thought, was the cause something else, not air filter?
- 2nd attempt — same as above.
- 3rd attempt — runs for about 10 minutes and stalls.
- 4th attempt — same as above.
- 5th attempt — runs for 40 minutes no problem before I turn it off.
So, apparently (and hopefully) the cause was indeed the air filter.
But I am struggling to understand the mechanics of the above behavior. If the stalling was caused by insufficient air pressure on low revs due to the air filter being clogged, then replacing it should have fixed the issue immediately. But instead, the issue appears to have gradually faded away.
Perhaps, the immediate cause was dust contamination of some engine parts due to the old filter letting some dust through? And now, the flow of clean air has cleared that out? But how exactly would that cause the engine stall on low revs?
As the comments suggest, the air filter may have only masked the real issue. Indeed, there was another thing that well could have been the cause:
Before I first encountered the issue, the fuel tank had only about 15 litres of fuel and I was going to refill it. I added about 50ml of diesel injector cleaner additive in the fuel tank (which I have virtually always been doing before refilling the tank). And right after it the problem first surfaced.
I am, however, hesitant to blame the injector cleaner because I have been using it for ages and never had any issues with it.