[PeterLa]

Hi,
I am brand new to this forum and hoping to get some help with my Daughters Kia Mentor 1.5 DOHC.
It is a great first car for her and only done 90,000ks. The engine light has been coming on and the the motor has been missing under light load intermittently.
After a visit to the local mechanic the engine light code was the exhaust sensor so I changed that. All great and no more engine light.
Now just need to get down to the miss under light load. I have serviced the motor and changed plugs and set to correct gap. No change in the miss.
I can help the miss by giving the motor a high rev around 6000rpm and that helps clear the miss for a while after that. I can plant my right foot and accelerate hard and the miss is not there anymore but comes back on light load.
Idles fantastic no miss at all.
Any help on other items to try would be greatly appreciated.

Pete

 

[GottaCruise]

Greetings,

If you are able to clear the miss by revving the engine / does not miss at idle, then I would lean towards an (ignition) or (fuel) delivery issue, rather than illegal air delivery,

If it was my ride, I would be inspecting the spark plug wires and ignition coil pack(s), and the wiring connecting the coil pack to the engine harness, then would do testing to make sure the plug wires where the proper resistance, and the ignition coils were the proper resistance..

On the fuel side, I would replace the fuel filter if old or suspect, and hookup a fuel pressure gauge to see if the fuel pressure is in-spec both while running, and holding pressure after being shut off,

If the car is equipped with an EGR valve, would also be inspecting the EGR valve, wiring, and vacuum hoses,

And would verify the ground points on the car are clean: the negative battery terminal -> frame ground, and the engine strap -> battery (or frame) ground,

--
After above, I would begin checking the sensors on the car (O2 sensor, TPS, MAF, Engine and Air temp sensors) to make sure they were in-spec,

Hope this helps,

Regards,
GottaCruise

 

[PeterLa]

Thanks for the great description of what to look at next.
Yes the motor does idle perfect after the fast rev so I will start with the fuel filter and coil packs.
Harness to ignition looks fine and no visable problems on spark leads but I will check resistance. Not sure what the coil packs should be though so any suggestion on that.
I will need the mechanic to check fuel pressure as I do not have a fuel pressure gauge.

Regards

Pete

 

[GottaCruise]

Hi PeterLa,

Unfortunately, I do not have access to any of the 1.5 DOHC motor info. (not used in US), so I can't help w/ the exact specs, but you could try:

A local auto parts store, they might be willing to let you take a resistance reading or have that info. on-line in their system,

The local mechanic, he may have access to that info. in his documentation.

* If the vehicle has separate distributor / an integrated coil pack within the distributor, I would see if obtaining a (used) distributor assembly from a local "pick and pull" / salvage yard is more cost effective, vs. replacing the coil pack separately..

Hope this helps,
Regards,
GottaCruise