Well, this is where my energy and funds have gone. My Toyota Opa, an oddity of a car, has been causing headaches for the past couple of months. From reliable motoring, to stumbling, juddering and just outright loss of power. Intermittently. Like all fun troubleshooting situations -_- Issue occurs across the entire RPM range. (Super rare on "unloaded" idle though - in neutral or park)
Couple months back, I completed a 120km delivery run, and returned to the shop I am based at. Shut it down for 20 mins, and then it struggled to start. From there it ran terribly...intermittently.
It only does this when in "closed loop". No OBD codes present, and Long Term fuel trims look fine. Short terms peg to +20 when it's playing up. I've done a ECU reset (unplug battery overnight) as well.
The parts cannon for this one resembles a GAU-8, and I've replaced;
- Spark plugs (Genuine NGKs)
- Oil change (Sakura filter, Nulon oil)
- Air filter (Sakura brand)
- One ignition coil (broke it when pulling them when replacing the spark plugs) (reputable aftermarket brand)
- Fuel Pump sock (same brand as coil)
- Fuel Pump (same brand as coil)
- Fuel filter (Sakura)
- In-tank fuel regulator (genuine Denso)
- All injectors with used Denso units, and then AliExpress knockoffs
- Cabin air filter (Pretty sure I replaced the original year 2000 filter... this has nothing to do with the engine issue, but check your cabin air filter!!)
Although, a lot of these items were due for service in any case, with the car having travelled 209,000kms. Some items had never been changed, like the fuel pump sock, fuel filter, and some hadn't been done since the car left Japan at 100,000kms, 14 years ago, like the air filter, spark plugs...
Power balance test (unplugging individual coils to see which cylinder isn't contributing) when it's throwing a tantrum has been inconclusive, with the engine stalling out if I disable any cylinder during it's temper fits. Fuel system cleaner has been used a few times, which helped... for a short time each time. Haven't used it since the fuel system filter replacements. The fuel system cleaner semi-working is why I've practically replaced the entire fuel system now..
I use reputable fuel (91 RON) from a local station that is very well frequented (and thus fuel is 'fresh')
Just did a MAF clean, but I'm wondering what to tackle next! At the end of this all, the car will have had allll it's services and it'll be good for another 200,000kms though!
When the car is behaving, it has all that pathetic 1ZZ power, but I can't travel more than 20 mins now without it throwing a wobbly... sometimes... ugh
It's a practical car, and I'm still paying it off - can't afford to replace it.
Anyone have any ideas before I take it to a mechanic? Whilst I could have done that from the start, the cost of the parts replaced thus far have cost around a normal "extended diagnostic fee" and I'm learning along the way.
