A friend has just rebuilt his 1ZZ with a brand new new short block from Mr.T, and a whole host of new bits and pieces
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( Timing chain, spark plugs, o2 sensors, Clutch etc etc
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).
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The exhaust manifold
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/ Precats have been replaced with a Toyosport Decat manifold, and the car has just the main cat present.
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The old precats showed damage a the tops, specially for the precat fed from cylinders 1 and 4
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- those also were the worst damaged.
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Following the rebuild, it has basically gone straight in for a MOT and although it passes the Idle emissions test, at fast idle
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(
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~1500rpm
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) the CO readings spike to
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~ 0.5.
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The same Cat on another roadster recently passed a MOT so the CAT is OK.
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OBD2 diagnostics at idle after the rebuild show the O2 sensors in the exhaust manifold are working OK and the output from the main cat is as you'd expect.
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Any ideas what could be done to narrow down the problem.
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Ideas so far as to possible causes
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:
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1.
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The ECU is still
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'learning' as engine is effectively being run in so low
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( below 4k
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) revs and low to moderate load, and has only been driven abut 20 miles since the rebuild? However car does idle at
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~800rpm indicating that the learning process has ended
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.
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.
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.
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?
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2.
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Coolant temp sensor
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: However Reporting coolant correctly
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3.
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Maybe the car isn't running closed loop on fast idle, as it does at normal idle?
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4.
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Possible problem with injectors? On rebuild, cylinders 1 and 4 were worst and showed evidence of running lean as exhaust values were blue.
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5.
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Possible marginal coil pack? However does run and idle smoothly without any lumpiness
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6.
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Dirt on the MAF causing incorrect readings?
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Other ideas and suggestions as to how to diagnose are welcome
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.
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.
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.
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!
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Ben