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Discussion Starter · #1 ·
Hi All

Read through a number of threads about rough idling and fixed on the Idle Air Control Valve (IACV) as the most likely cause.
I checked for odb codes and none appeared, so I removed the IACV and cleaned with carb cleaner.
Replaced and start up first time, but still running rough.
Switched off , then would not start without me revving the engine and keeping the revs high (1200) for 10 or so seconds, then it settles down to rough idling again.

I've rechecked the codes and I've now got P0170 Fuel Trim (Bank 1) and P0370 Camshaft Position Sensor A Circuit (Bank1 or Single Sensor).

Little help please.

Cheers Ian
 

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MG TF
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It does sound electrical, is the battery/alternator voltage around 14V when the engine is running?

A failure of the camshaft sensor is a known issue on MPI engines however it doesn’t usually result in poor running.

If your OBD scanner can do live data what is the output from the pre-cat lambda sensor?

Do you know when the coil packs and leads where last changed?

When was the cambelt last changed, I guess that there is a chance that it may have slipped by a tooth and the crank and cam shafts are out of sync.
 

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Discussion Starter · #5 ·
It does sound electrical, is the battery/alternator voltage around 14V when the engine is running?

A failure of the camshaft sensor is a known issue on MPI engines however it doesn’t usually result in poor running.

If your OBD scanner can do live data what is the output from the pre-cat lambda sensor?

Do you know when the coil packs and leads where last changed?

When was the cambelt last changed, I guess that there is a chance that it may have slipped by a tooth and the crank and cam shafts are out of sync.
I'll check the voltage later today, the pre-cat lambda sensor is about 18 months old. My odb doesn't do live data. Coil packs and leads could be the originals as I've not changed them.
Cam belt has only done 5000 miles max.

I've ordered a new IACV sensor and camshaft position sensor.
Hopefully that will sort it, if not I'll have to take it in.
 

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'06 MG ZR +120 (HQM) '04 MG ZR 105 (IAB)
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P0370 is related to the timing sensors (crank and cam). It suggests that the engine ECU is either not recieving pulses from either the crank sensor or the camshaft sensor, or that it is recieving pulses that conflict. This will obviously cause rough running as the ECU will be unable to get the timing right.

Before spending a lot of money on randomly replacing parts, I would start by examining the wiring related to both sensors, including connectors both within the wires between sensor and ecu and the connector on the ecu itself. You could then try testing the sensors themselves to see whether/which one is faulty. I would say there is a good chance that it is either a faulty sensor or a damaged wire.
 

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MG TF
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Presumably you have done a throttle position sensor re-set?

 
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