Hello Scotty and community!
I have a 2013 AT 4WD Kia Sportage. It's a bit different from the US version, as it has a 2.0L G4KD engine, as opposed to US's 2.4 G4KE one. I bought it used last autumn and it's been pretty good and fun to drive so far, except this idling problem that pops up every now and then.
The short term fuel trim on this car usually bounces between -2% and 8%. When the engine gets warm, its idle speed drops to ~620 RPM and sometimes the first oxygen sensor starts reporting that the air-fuel mix is running too rich and the fuel trim starts going down really fast until it reaches -30% and stops there. When it does that, the engine starts shaking like mad and its speed jumps between 500 and 1,000 RPM.
I have to press on the accelerator pedal and hold it for a couple of seconds to rev it up to at least 1,500 RPMs so the fuel trim goes back to 0% and it runs smooth again, but when I take my foot off the pedal, it goes back to -30% and shaking like mad in seconds.
The check engine doesn't light up and there are no error codes found by the OBD-II scanner.
I assume that negative trim may mean that the engine isn't getting enough air, so I changed the air filter and cleaned the choke with carb cleaner, but it had no effect on this problem (but the car does go smoother at low speeds now). What should I check next?
I have a dump of live data from the OBD-II scanner so I can attach graphs of any metric that can help, just let me know.
Best regards from distant lands of Siberia! 🙂
I could've mixed up the terms here a bit — I cleaned the throttle body, one that controls the airflow on intake. 🙂
Also, this G4KD engine doesn't have any kind of supercharger or turbo, so that can't be a problem here.
The engine is a twin brother of Mitsubishi's 4B11 (used on Lancer and some Outlander versions) and, IIRC, Chrysler "World" engine (Dodge Caliber, Jeep Compass).
So, after 2 months of poking around I finally found the root cause of the problem. 🙂 /p>
Turns out, it was caused by poor ground connections (i.e. wires that connect car's body and some of it's components). After cleaning them and re-connecting everything back (and tightening them well) the problem finally went away in it's entirety — no more poor shaky idling, no more lights pulsating, and the car runs like a dream again.
If anyone has a similar generation Kia Sportage or one of it's twins (Hyundai ix35 and Tucson), here's what you need to check (part numbers mentioned here are for European cars and may be different for Korean and American ones):
- First and foremost, check the cable that connects the battery's negative terminal to the car's body. It's connected to the body using 2 M6 bolts that tend to get oxidated and corroded. Take these off, clean everything and connect it back using new bolts. Be careful, as these bolts can break apart when removing them. Keep in mind that this cable has built-in battery current sensor that can be useful in certain situations, so this cable is a bit more expensive than the others. P/N: 37180-3W000
- Next, there's a cable that connects the body to the engine block. This one is responsible for proper voltage supply of everything that's connected to the engine (sparks, fuel injectors, throttle/choke body, etc.). P/N: 91860-3U210
- And last, but not least — there's a copper braid-like cable that connects the body to the transmission case. If this one goes bad, expect janky gear shifting and nasty kicks every now and then. P/N: 91860-3U410
In my case the cables were alright (except that transmission braid-like cable, which is a bit worn out) and I only had to clean and re-tighten all the connections.
Well done! And thank you for keeping us posted. I’m sure it may help somebody, in future.
Sounds like your MAF sensor is "over-reporting" airflow and the computer is adding too much fuel for the actual amount of air.
The upstream O2 sensor is reading the rich condition and attempting to "lean" the air/fuel ratio.
(negative fuel trim)
Your MAF sensor may be dirty or failing.
Maybe get a can of MAF cleaner and first try cleaning your MAF sensor.
If that doesn't work you may want to consider replacing it
Thank you for your response!
I'm not sure if this particular engine has a MAF (or MAP) sensor, but I'll check it next time I get my hands on the car and report back.
Hello again @jack62!
The problem went away, as it seems. Had no idling issues since Jan 22, but it got a bit colder though (down to -21…-36°C). Will see if it happens again. I checked the info about air intake parts of this engine, and it has a MAP (air pressure) sensor installed right after the throttle assembly.
Also, I re-checked the OBD-II sensor records of when the issue was there and now and the only thing that was different (besides fuel trim) was something called "commanded evaporative purge" — it was fixed at 2% the day I encountered the issue and varied between 0% and 98% when all was OK.