Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
2011 Daihatsu Terios.
1500cc.
O/D Light flashing and its in limp mode. Long term Fuel trim were very negative at idle and would improve when you press on the throttle.
Upon diagnosis it was found that it was a vvt system code and a LTFT of -43% at idle.Long story short, the timing chain was stretched , the vvt solenoid strainer was clogged.
Vvt gear, timing chain , vvt solenoid, and chain tensioner were changed. Check engine light is off and vehicle out of limp mode. But there is still a negative LTFT of 25% at idle.
I thought the vvt system was the cause of the negative trim at idle. Negative trim improved . But only by about 15% .
I have checked for leaking injectors by scoping them and looking for the closing hump. I have checked the purge valve and disconnected it . I have disconnected the pcv incase the rings are bad and vehicle is leaking fuel into the oil but again no improvement on the negative trim at idle.
My last suspect was the IAC. Which was stuck but cleaned seams to be working.
Duty cycle goes up under load. Idle is steady at about 650rpm.
It only has s MAP sensor for air flow.
The vehicle was also overhauled when changing the the vvt system.
I need some help in figuring why the negative fuel trim at idle.
I have tested a number of similar daihatsu's and they all have high negative trims at idle.
Also thought it might be negative because of vvt system was tuned to lower the injector pulse width at idle for econnomical reasons.
Also, I'm not familiar with that injector scope test but maybe try an injector balance test there? I've seen leaking injectors on my bench flow test machine that electrically appear to be sound but still form drops. Maybe you can explain that scope test and how it works here to educate me on it though, since it might cover the balance test too.
Injector balance test is my first though but the oxygen sensor could be lying . I would also do a sanity check on the MAP and IAT are the readings key on engine off in the right ball park.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I'm not familiar with that vehicle but here are some other ideas.
- High Fuel Pressure Check (Pressure Regulator Leaking or Faulty?)
- Internal Fuel Leaks? Not sure if this has an external fuel rail or internal (cast in)
- Timing is Good?
- Verify Upstream O2 with Downstream O2 after reseting fuel trims. If down stream is reading rich and upstream is reading lean it might be an upstream O2 problem.
- As Andy said, Injector Balance Test & MAP and IAT sensor verification check with engine off. Maybe grab a value off another good running vehicle for the map with engine off as I would expect KOEO voltage of most MAP sensors to be roughly the same at atmospheric pressure. At least check the pressure value it reads and compare to other known good sensors on other vehicles if voltages are different.
Colleagues!
I have Daihatsu Sirion 1.0 of 2008.
The Same problem LTFT -43%.
All that is described above is checked all right.
There are still suggestions that it can be. Maybe someone already decided to solve the problem !?
