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Hi guys! Have a problem that has been persistent the last 30,000 miles that I’ve owned this car. Currently at 175,000 miles. This is a Corolla with the 2ZZ-GE motor (VVTL-i).
I’ve been struggling with an intermittent (once or twice a week) high-RPM, high load misfire (8000+ RPM) ever since I’ve gotten the car.What I’ve replaced:
Spark plugs (checked gap, too), coil on plugs (all 4), fuel injectors (all 4), fuel rail (for a high flow aluminum one), fuel pump (again with high flow), mass air flow sensor, all intake gaskets (intake manifold, throttle body, etc), PCV valve, O2 sensors (front and rear), throttle position sensor, added additional grounds between chassis and motor/transmission, I even swapped the ECU for a known good one, still does the same thing.What I’ve checked:
Compression (210-215psi across all 4 cylinders), leakdown tested (5-7% leakdown across all 4), smoke tested intake system (still replaced gaskets anyways), wiring harness integrity (pulling/shaking harness while running), valve cover and spark plug tube gaskets are intact and not leaking on the COPs. Valve cover was removed to change the gaskets, all camshaft lobes (high and low lift) look fine, valve clearances are at the loose end of spec, but are still in spec. OCV filters (for VVT and VVL) were both checked, no particulate (cleaned them anyways), tested functionality of VVT and VVL control valves via Techstream (both work just fine). Swapped locations of spark plugs, coils, and injectors between cylinders (stays with #1).I’m probably forgetting some of the stuff that I’ve done/checked/replaced, but you get the point. I’m at wit’s end trying to solve this misfire. See if someone with a bigger brain than I can help me out. Car runs perfectly fine 99.9% of the time. Always filled with 93 octane at low altitude, 91 at high altitude.
Thanks in advance!
Justin
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Replies
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Does this miss fire trip a CEL?
Have you checked valve adjustment(s)?
Does the engine have variable valve timing ?, it may be off but not out of spec.
Have you checked for any exhaust leaks (cracked exhaust manifold etc.) ?
What about a possible restriction in the exhaust system or faulty cat.?
Just passing thoughts considering what you state you have replaced already.Might be a good idea to plug in a scan tool and check live data when this occurs to try to find the cause.
Nightflyr is right for checking the stupid stuff first. But if that doesn’t pan out, then you may want to consider these possibilities:
Failing valve lifter or spring? Since this seems to be happening mostly at high RPM, a lifter that’s just beginning to fail may allow the valves to float here. Or a cracked or damaged valve spring could also have the same effect. It would measure fine when checking the lash but not perform as well as needed at high RPM.
Coolant entering the combustion chamber? A compression test may not necessarily find this if its minor. Though I would think the plug would be white. You could boroscope the cylinder and look for a unusually clean combustion chamber. Also, you could get a test strip for your coolant to see if there are traces of exhaust gases.
Misfire does trip a CEL. Flashing CEL. Valve adjustment is on the loose end of spec, but still within. It does have VVT, never had any faults for it, and testing via diagnostic software shows it to be OK. Haven’t checked for exhaust leaks, but I no longer have a catalytic converter. Exhaust system is all new, no restrictions should be present. I have tried to log data via Torque Pro, but nothing looked out of whack to me (sensors dropping out, noisy signals, etc)
Engine doesn’t have lifters. They’re shimmed. My gut says it’s not a valve spring, because I’d think it would misfire more often than once in a blue moon. Spark plugs all looked normal, not even burning oil. Coolant level has stayed more or less the same since I changed the thermostat out 20k ago or so. Haven’t tested for HC in the coolant though..
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