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Matt
Matt, Engineer
Category: Kia
Satisfied Customers: 20585
Experience:  Mechanical Engineer BEng Hons22 years experience in car engine industry, 10 years in formula 1
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I have a 2004 Kia Optima that won't run properly. It chugs

Customer Question

I have a 2004 Kia Optima that won't run properly. It chugs and sputters when you push on the gas. Can't seem to get a good reading on the computer codes. I have replaced the Mass Air Flow Sensor and the Throttle Position Sensor to no avail, nothing seems
to work. My mechanic didn't know what to do and basically gave me back my car and threw his hands up in the air. HELP?????
Submitted: 1 year ago.
Category: Kia
Expert:  Matt replied 1 year ago.
Hello
This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.
As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.
Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.
The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.
Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.
It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine
Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.
if the engine condition is the same then chances are the meter or the connection to it is faulty
Air leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.
This leads them to be quite intermittent in the case of mild leaks
its also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residue
On no account touch the sensor wires with anything physical as they are extremely fragile
Customer: replied 1 year ago.
Thank you, ***** ***** try all of this and let you know what i find out.
Expert:  Matt replied 1 year ago.
No problem
Expert:  Matt replied 1 year ago.
Hi
do you still need help?