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Matt, Mechanical Engineer
Category: Car
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Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 2004 Kia Mentor 1.6i which has starting problems

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Hi, I have a 2004 Kia Mentor 1.6i which has starting problems when cold and has poor throttle response below 3,000 rpm until the engine has warmed up a little. When trying to start the car if I crank it over 6 or so times it doesnt try to fire up, try again and it will try to fire and usually on 3rd or 4th attempt it fires straight away will rev initially but is then very fluffy until engine warms up. I have checked fuel pressure on start up and it is there as soon as ignition is turned on, new spark plugs, coils and HT leads have been fitted as these were in poor condition. There are no fault codes in engine ecu and temp sensor, air flow meter, 02 sensor etc readings are all as you would expect them to be. The emissions are spot on as just had an MOT test.The car starts and runs fine after approx 2 mins warm up.
Submitted: 1 year ago.
Category: Car
Expert:  Shantal-Mod replied 1 year ago.
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Expert:  Matt replied 1 year ago.
Hello This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;Airflow meterCrank position sensorCam position sensorO2 sensorThrottle position sensor Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40 and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins. Check the resistance of the spark plug leads ( 13-15Kohm / metre) and replace if any doubt or high resistance - Also replace the spark plugs if any of them fail this checklist: http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp Also its worth checking that the electric pump that feeds the injectors is working correctly, it should run for a few seconds then switch off when you first turn the ignition on. If the connections to this are corroded or damaged then the pump could stop at any time. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse, ideally measure the voltage at the pump and check its getting 12V Also check for exhaust leaks before the o2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21607
Experience: BEng hons Mech engineering, in auto industry 22 years
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Expert:  Matt replied 1 year ago.
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