My Citrus tends to stumble and lack power in lean burn when it is under increasing load. When it exits lean burn, there is a gentle burst of acceleration. I hope to uncover why. Items I'll be looking at:
Have I missed anything?
I won't look at all of these areas if I find the root cause before I get to them all!!!
I have already looked at several of these areas, but have decided that I need better data. OBD2 is too slow, so I plan to measure a number of sensors in real time, with many samples per cycle of whatever I'm measuring. This includes
Any ideas for measurements are welcome. This will probably start in earnest between Christmas and New Years.
Item | Status | Notes |
EGR valve | Replaced with measured good used valve, then with new valve. | The original was terribly intermittent!!! And, don't reuse gaskets. Use a new gasket. The kind stamped out of a thin metal sheet may leak. |
EGR plate | Cleaned | Was plugged!!! |
EGR passages | TBD | |
Spark plug indexing | Correct plugs for engine | |
Spark plug age | Replaced | No change in high load lean burn performance with new plugs |
Spark plug coil performance | New coils installed, no difference, old coils back in. | No sign of rust or delamination. Still worth testing. Corrosion possible in spring wires inside boot. Measured current draw of primary and found all three the same. New ignition coils made no difference. |
LAF sensor | Replaced | This is pretty much something that has to be done if the LAF sensor is aged. It is a very important sensor. |
Manifold pressure | No smoke leaks except very small amount at EGR valve bearing (old and brand new valves) | OBD and trim values suggested there might be a small leak. Smoke tester revealed a very small leak at the EGR valve sleeve bearing but this may be normal. |
Fuel injectors | Cleaned | ABSOLUTELY IMPORTANT. Low flow rate in an injector can lead to loss of catalytic converter. NOTE: Non-OEM projectors like Ultra-Power may have different flow pattern. Insight flow pattern appears to aim to normal and VTEC ports and have been designed to balance lean burn and high RPM use. Stick with OEM here. Unsure if age impacts atomization even if cleaned - this should be confirmed. The old injectors definitely show a flow imbalance. Do not reuse the seat seals or vacuum leak, possible imbalance. A hack is needed to keep dirt out above the seal if the cup type is not available (appear no longer available.) Needs more study, later |
Fuel pump pressure | Checked good | Well over 60 PSI |
Fuel rail pressure regulator | Replaced | Original unit replaced with one from another Insight before pressure testing; no difference. Replaced unit shows 41 PSI at tip at different vacuums. New unit shows 43.5 PSI. No apparent difference in performance. |
Engine Deposits | After 7000 miles of Sunoco 93 and Techron, removed about 20% of deposits. May need to perform full cleaning. | In past work, cleaning piston heads seemed??? to help but lasted only a few hundred miles after which deposits reformed. Not sure if there is anything to see here. We know that deposits raise cylinder pressure a little. Wonder if they affect boundary area flow in a way that creates turbulence and may modify mixing. Really need to borescope one of the few well-performing low mileage Insights to gauge this. Wondering if turbulence caused by disruption of the boundary layer by deposits is causing poor mixing in the cylinder and leading into misfires or partial combustion that could be limiting power or possibly introducing knock. Just a WAG and as likely to be wrong as right. |
Valve lash | Good | This does affect performance and should probably be checked every 30K miles or so. If out of whack, tuning this can make for a smoother idle. |
Leakdown test | Good | Leakdown test showed excellent results in two cylinders and good results in third. Leakage in center cylinder might be due to a few visible scores likely caused by abrasive entering and getting stuck between piston head and wall before dislodging. |
Borescope | Using one with side cameras to be able to see the valves and cylinder top | Since cleaning the injectors and doing some long road trips with 93 octane Sunoco, the cylinders appear to be getting cleaner. But beyond a certain point cleaning appears to have slowed. |
Valve guides | TBD | Inclined not to worry about this with the good leakdown test. |
Exhaust System | Being replaced | Catalytic converters melted likely due to injector imbalanced from low flow rate due to varnish etc. |
Compression / worn rings | Good. Measured 200/195/205 | Leakdown test suggests these are not a concern. |
ECM / control loop issues | A02 and 505 ECUs behave similarly | A 4.88 Hz signal permeates readings of sensors, and they are also modulated by fuel injector current. This may be normal but it might align with jerkiness. Theory that it might be modulating the AFR readings. Needs more investigation. Examination of a well sorted car is desirable. |
Knock sensor | Appears to work properly; broke during replacement. Knock sound and knock retard scan values are closely correlated. | In taking a longer look at OBD real time parameters, knock retard was observed. It is greatest during deep lean burn and correlates closely to knock sound in engine and drop in performance during lean burn. |
Have I missed anything?
I won't look at all of these areas if I find the root cause before I get to them all!!!
I have already looked at several of these areas, but have decided that I need better data. OBD2 is too slow, so I plan to measure a number of sensors in real time, with many samples per cycle of whatever I'm measuring. This includes
- Manifold air pressure
- IAC valve position and changes
- EGR valve position
- LAF sensor (A/F ratio)
- Injector pulse width
- Changes in pulse width
- Timing advance
- Crank sensor
- Throttle position
- Camshaft sensor
- Instantaneous changes in RPM
- Correlation between instantaneous RPM change and instantaneous fuel injection change (deviations may imply misfire)
- AFR imbalance as detected through LAF sensor (this will be a challenge!)
- Some OBD2 parameters I can't measure, such as fuel trims, knock retard, etc
Any ideas for measurements are welcome. This will probably start in earnest between Christmas and New Years.