Hey all, need some advice with my 87 M20B27...
After about 20 minutes of driving from an overnight sit and during mid-day restarts, I get a pretty bad intermittent misfire. Usually happens under moderate to high load, if I limp it along I can usually avoid it for the most part. I've noticed that before the car warms up the idle stays at 600-650 but when warm it goes up to 900-950. Also when the car is overnight cold, it fires up with 1-2 seconds of cranking but when warm it takes 4-5 seconds.
What I've already done is listed below.
Inline fuel pump (255lph)
Fuel filter
Hose clamped the in-tank rubber connector
Fuel tank and pickup screen are clean
Replaced fuel injectors with fresh rebuilds
Tested FPR (vacuum unplugged goes up to 2.5 bar, idles at around 2 bar)
Tested fuel pressure, 2 bar at idle and goes up to 2.5 bar under load
AFM tested using the 9v voltage drop test (not the resistance test)
CTS tested within spec
Coolant temp switch tested within spec
TPS tested within spec
Unplugged O2 sensor (was getting bad "stair stepping" acceleration along with the same misfire when plugged in, need to troubleshoot that another day)
New plugs (NGK copper)
New wires, cap and rotor
No obvious vacuum leaks
Replaced the main relay and fuel pump relay with known good relays
Based on everything that has been replaced and/or tested, I'm at my wits end. I'd say the only things left are the ignition coil or the DME.
Any other thoughts?
After about 20 minutes of driving from an overnight sit and during mid-day restarts, I get a pretty bad intermittent misfire. Usually happens under moderate to high load, if I limp it along I can usually avoid it for the most part. I've noticed that before the car warms up the idle stays at 600-650 but when warm it goes up to 900-950. Also when the car is overnight cold, it fires up with 1-2 seconds of cranking but when warm it takes 4-5 seconds.
What I've already done is listed below.
Inline fuel pump (255lph)
Fuel filter
Hose clamped the in-tank rubber connector
Fuel tank and pickup screen are clean
Replaced fuel injectors with fresh rebuilds
Tested FPR (vacuum unplugged goes up to 2.5 bar, idles at around 2 bar)
Tested fuel pressure, 2 bar at idle and goes up to 2.5 bar under load
AFM tested using the 9v voltage drop test (not the resistance test)
CTS tested within spec
Coolant temp switch tested within spec
TPS tested within spec
Unplugged O2 sensor (was getting bad "stair stepping" acceleration along with the same misfire when plugged in, need to troubleshoot that another day)
New plugs (NGK copper)
New wires, cap and rotor
No obvious vacuum leaks
Replaced the main relay and fuel pump relay with known good relays
Based on everything that has been replaced and/or tested, I'm at my wits end. I'd say the only things left are the ignition coil or the DME.
Any other thoughts?
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