Re: Lean Misfires at 2700-2800 rpm
I tested a known good ECU today and I still have serious lean issue at 3000RPM.
2nd Gear, no boost, at 2800RPM my AF is 13.9 but at 3000RPM it is 16.0, by 4000 RPM it is back to 13.9.
One thing that it might be. I did the vacuum hose reduction because my fuel pressure selenoid seemed to bw working erratically. The fuel pressure selenoid reduces fuel pressure at idle. With it bypassed my car now idles at 13.9 instead of 14.7. I wonder if the ECU is leaning out the fuel too much and when the car is normally getting full fuel pressure the ECU is just not adding enough fuel?
The porblem with this therory is that I had the same problem when I had a fuel controller installed. I was suing the fuel controller to lean mixture out to 14.7 at idle w/o the fuel pressure selinoid.
What we really need is a list of all the passible causes and what to check.
For example:
Possible causes:
1. Bad Ecu: Check by borrowing a good ECU from a friend
2. Spark blowout: Reduce plug gap and see if problem gets better
3. Bad MAF Sensor: Check by borrowing a good MAF sensor from a friend
4. IAT Sensor, Intake air tempuratue sensor, Check Datalog and make sure value is normal, My car's intake tempuratures are usually 30-60 deg hotter that outside tempuratures when idling and only 20-30 deg hotter than outside when cruising (no boost)
5. O2 sensors, check that ALL O2 sensors are cycling normally at idle
6. TPS Switch, Use datalogger to check the TPS switch, it should switch from on to off if you press on the gas pedal at all, and it should switch from off to on when you left off the gas completely
7. TPS adjustment, Datalogger should show between (8 and 14 ???) at idle and it shoudl increase to ??? when gas pedal is fully depressed.
8. Vaccum leaks, Use an intake pressure tester adn eliminate any boost leaks.
Anything Else? Coolant temp sensors? Electical connections, ground wires?????
I probably should re-prioritize the list so that anything that can be checked with a datalogger is checked first.
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