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Im sure its been posted before (because I have posted it before) but here is a step by step: 1) Verify spark:
a) Remove coil pack, insert spare (good) spark plug. With car running, ground spark plug to manifold, verify spark. If spark present, move to 2, no spark move to b.
b) Swap coil packs with another cylinder. Misfire follows cylinder, coil pack issue (replace coil pack). Misfire stays on cylinder, wiring issue (generally PTU or PTU subharness) 2) Verify fuel:
a) Check injector resistance with DMM (generally ~12-14 ohms). Passing result, move to b. Fails resistance test, replace injector (failed injector).
b) Check resistor cycling. Using 9v battery, connect wires to each lead, use wires to excite injector (should audibly click). If injector clicks, move to c. No click, failed/stuck injector (usually discovered with DMM first). Remove injector, soak in WD40 for 24 hours, try again (second fail, replace injector).
c) Verify signal. Plug a noid light into the injector connector, start car. Verify noid light is lighting. If lighting, move to 3. No light, flip noid light around (verifying polarity). Still no light, signal issue, move to d.
d) Verify signal wiring. Using DMM, verify continuity of injector signal wire between connector and ECU (use pinout diagrams to determine wire location. Continuty, move to e. No continuity, locate and repair wire break.
e) Verify signal power. Use DMM to check continuity between injector connector and battery positive with ignition 'ON'. Continuity, move to 3. No continuity, locate and repair wire break. 3) Verify compression:
a) Warm engine fully (running for several minutes past operating temperature is sufficient). Remove all coil packs, spark plugs, and balance tube. Check compression for each cylinder. Compression within spec (Varies depending on engine age, but cylinder to cylinder variation should be less than 10%), move to 5. Compression low (No real rule, but I find that 100psi minimum to even fire a cylinder, and a healthy TT engine should be 140psi min), move to 4. 4)Verify leakdown:
a) Return engine to fully warm, rotate engine to TDC of the compression stroke of the cylinder being tested, using compressor and following the directions of the leakdown kit you have, check leakdown to determine where the compression is being lost. Air exiting intake manifold, intake valve(s) leaking. Air exiting exhaust, exhaust valve(s) leaking. Air exiting crankcase (check via oil fill cap), piston ring(s) leaking. Repair as necessary (i.e. rebuild). Leakdown < ~10%, move to 5 5) Cry a little, start back over.
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1992 300ZX NA 5 Sp (Dead)
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1990 300ZX TT 5 Sp (Stock Turbos) (Est. 400 HP)
1990 300ZX TT 5 Sp (GT600R) (Est. 600 HP)
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2008 Honda Civic (DD)
2014 Nissan Murano (DD)
1969 Chevy C10 (Toy)
1969 Chevelle (Toy) |
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