Article : Project EFI engine performance while no error code
Work performed on : Toyota Platz 1.0L
Year : 2000
Engine : 1SZ-FE
Symptom and issue:
1-Low power, load on AC and ramp.
2- Engine pick up hesitation in between 1200 to 1500 RPM
3- Lower fuel average 9– 11 km/l City drive
4- Engine efforts to reach speed 100km/h
5-Hard paddle to accelerate
6- RPM decreases while on D or R brake pressed, results engine vibration.
Maintenance history:
According to different mechanic and electrician car is at best performance no error codes. The average is best as 11km/l. On forced they started to suggestion to changes the numbers of sensors for better May better performance results.
Finally I said GOOD BYE to all mechanic hazrat whos approaches to limit but only tuka lugana, by changing bla bla bla…. I realized I will waste my money and time. Finally I owned performance matter project by self.
Data analysis:
Based on real time data analysis following logs are recorded:-
1- Engine idle around 800 RPM
2- MAF sensor reading is fine accordingly g/sec at idle
3- TPS sensor output data shows perfect no missed slopes in graph
4- O2 sensor frequency varies in between data .1 to .9, probably ok
5- Engine temp normal , fan trigger on at 93 c and off at around 86 within 2 minutes.
6- STFT frequency range at idle 0 to +3-4
7- LTFT frequency range at idle +1.75 (Based line crated by ECU)
8- Intake air Temp average 45C
9- fuel pressure 50 psi (perfect)
10- cylinder compression test: 170 to 180 psi
Findings 1
Every things seems to fine but at closer observation O2 sensor data reading to .1 to .9 means data at maximum span and most important LTFT based line at idle +1.5 tells me the engine running lean and ecu adding fuel to gain stoichiometric of AFR. At ideal conditions it should be 0 in graph. Second thing STFT where also 0 to + values. On closer look while rpm increases, results LTFT slope down to negative on higher Rpm. This sign help me to know there is air intake happening from somewhere . Ecu usually push code for lean or rich trim issue when value triggered around +- 25 to 30% that is not in my worst case
Finding 2
It is noticed when quick push paddle for acceleration kind of buzzing noice heard from engine side seems some gasket leaks from exhaust. Note : during performing engine compression test , it is found oil deposits on spark plug valve wall and on ignition coil tube side, compression test results found satisfactory.
Finding 3
Shifter on N normal idling 800rpm , shifter on D or R , engine Rpm decrease and vibration while break pressed
Fixing of finding 1 & 2
Verified the sensors outputs, volts , resistance and connectivity of MAF, O2, AirTemp, ECTemp, IAC valve , EVAP value, TPS, Fuel pump pressure, compression . Every things found fine , performed cleaning and install back.
Services performed:
Verifying possible air intake area and fixing followed by given checklist:
1- MAF sensor O ring
2- Air folder assembly to throttle body
3- EVAP Air intake
4- Break booster Vacuum section
5- Throttle body to intake manifold assembly
Others verifications:
1- fuel injectors nozzle tests , no issue found installed back after service
2- Check fuel pulsation damper functionality
3- Exhaust examination : no any air leaks found in between O2 to exhaust manifold. Cat converter is not installed in such car case so cat clogged test not performed
Fixing of finding 3
According to service manual 1st-fe engine idle RPM should be in between 700 to 750, set the throttle body butterfly closed by adjustment of screw. Set the IAC value to fine idle recommend range 750RPM at 80c engine operating temperature
Reason of issue observed:
AT transmission started to engaged with engine above 800rpm , higher Idle rpm caused bit Transmission engaged while break push against engine to lower rpm results. Issue is resolved by lowering idle RPM
Conclusion and results:
According to addresses issue was caused of lowering engine power is to spark plugs seals leakage and buzzing sound. After servicing and tighten properly engine power issue is resolved. High acceleration while soft paddle
According to LTFT + base line (lean engine)was caused by minor air intake to compassion chamber (not calculated by MAP) order to be added more fuel to maintained AFR as results + fuel adjustment by ECU. Air intake issue found from O ring in between manifold to throttle body fitting . Refer to Figs LTFT back to 0 at idle . Span of O2 sensor also decreased .9 to .6 average. STFT maintained +-5 on higher RPM.
Achievements:
Engine smooths as newer , soundless increases power and acceleration, enhanced fuel average from 11 to 17+ City drive . Refer to Fig testing driven 9km , average speed of 20km/h, average calculated 17+ km/L
Key points:
To achieve engine performance intake and exhaust should be air tight. No pressure should be noticed in between cat converter and upstream O2 sensor banks
