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Help with High HC @ idle for vehicle registration. 700 1991

Hi,

My 91 740 B230FT, M46, wagon has a high idle (1400 rpm)& higher than spec for HC at idle (492 vs spec of 200). The engine is a bit rough idling.I have to fix the Hi HC for a licence registration.
My ECT (in car now)for both ignition & FI (LH2.4 and EZK)reads 10K ohms @ 4ºC spec is around 5K. I have a NEW ECT that reads 10K @ 4ºC & a used one that reads 5K @4ºC. Just how much difference does this make?
The ECT in the car reads as per spec @ 40ºC. I haven't checked the others.

The TPS is good & adjusted, the IAC valve is brand new, the O2 sensor is my next check. The throttle body is clean.

I heard an intake manifold area hiss (leak?) earlier but it disappeared & I don't hear anything w/ a hose & stethoscope.

Any help appreciated








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Help with High HC @ idle for vehicle registration. 700 1991

It is running very rich, as you know. Read this post: http://www.brickboard.com/RWD/volvo/1330239/740/760/780/cold_start_issue_finally_fixed_buck.html

Check your vac lines and I'd recommend getting friendly with a vacuum gage.







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