Odd Kia Optima issue

[sandt38]

I have a 2006 Kia Optima in my stall right now. VIN KNAGD126765464907, 2.4l DOHC California Emissions with a manual transmission. The vehicle surges radically at idle. Another tech had it in his stall and he came up with a TPS code, and subsequently replaced the TPS. He has since put on a MAF and IAC motor, all from Worldpack to no avail. So now it sits in my stall.

It surges, sometimes with consistency and other times just oddly, from 1800 RPM to 500RPM. It currently has no codes aside from those I am setting. In looking at data I see it goes to open loop when idling high to closed loop when low. In closed loop it goes dead rich, 1 volt at the O2, 10MS duration on the injectors, and the MAF read ~2V. In open loop the O2 cycles a tad rich, but it moves well, 2MS on time, and the MAF reads 1.2. All data has been verified via the scope. In closed loop my trims go to -20$, in open, as expected 0. I am not surprised at this as my previous info indicates it should read this way. Vacuum when it surges low is 21 in, and about 19 when idling high. Closing off my incoming air stalls the car, closing off the IAC passage drops my idle to ~500RPM. I have checked and no vacuum leaks are found. EGR has been blocked off, canister purge has been blocked off, and still no good. I have checked all grounds (both through voltage drop- no more than .02V on any sensor, and by creating my own grounds), and those stupid ground splices that Kia likes to use. I do not lose any voltages (checked all sensor references and all 12 volt lines). Fuel pressure is a steady 48PSI, volume is good, and fuel quality is good.

All my inputs seem to be correct.

If you disconnect the IAC it still surges the same. If you disconnect the MAF it goes full rich and idles at ~500RPM, and my surge goes away. I physically checked my cam timing, and all keyways for slippage, because I did not like my cam/crank data...



Yellow-cam, green-crank, Blue-ignition

The majority of the patterns I viewed on Kias show my leading edge of the crank to closely correspond to the cam, where mine does not.

Anybody have any input? I am tempted to put a brain in it, but I have so little experiance with Hyundai/Kia, and I just don't know about them having ECM issues.

[sandt38]

Oh yeah... coolant temp looks right as well.

[D1353L]

Does this 2006 Kia have electronic throttle body? Probably not if it has an IAC. I would want to look at desired idle, iac counts, fuel trims, whats the upstream O2 sensor doing, how many miles are on the car. Fuel injectors can do screwy stuff when their clogged partially, but 1800 rpm, I don't think so. An old tech when I was working at Ford said when diagnosis is giving you trouble start disconnecting sensors and actuators to see if and when the problem changes, does it get better, for instance if you disconnect the IAC. After hearing that discription sounds more like an air flow issue after you disconnect the MAF and the idle goes low. Also don't overlook charging voltages and too much A/C ripple at the battery can cause trouble. I seen a mazda turn into a lemon at a dealership, after they replaced the engine, the PCM, and a host of other components and all that was wrong with the car is that it had a bad/marginal battery that threw the computerized charging system off. The car would start no problem, but the computer didn't like the battery for some reason. If your are gonna replace the PCM, just make sure you have all your basics checked at the computer

[sandt38]

Well after a day off for my youngest son's graduation I got back to it today. I thought about it quite a bit, actually and decided it had to be a fuel delivery issue, obviously based on computer control rather than mechanical. Kia is rather vague in their info, and only provided a resistance spec for the TPS, rather than a voltage. So I took a shot. Specs were 1.6Kohms at idle and 2.4Kohms at WOT. On the car it read 1.8Kohms and 3.3Kohms. So I grabbed the old TPS and checked it. It was close to being within spec so I plugged her in and BAM! she idles fine. I suspected the base 1 volt at idle (the replacement sensor value) was fine, but you all know what happens when we assume...

Ironically the initial component swapped was the TPS, and I was led to believe the issue did not change. In talking to the tech he said it was initially just a high idle issue, switching to a surge at idle after TPS replacement. I have a funny feeling it was really the MAF sensor at fault initially, and swapping out the TPS compounded the issue, but I am just going to toss on a factory TPS and call this done.

FWIW the voltage spec appears to be ~.3V at idle.

[8ftsq]

Could be way off base here but..... when you replaced TPS, did you reflash ECM with latest software? I would not go any farther until you have done this. I work for Hyundai and have done similiar procedures on Sonatas. In my estimation, engineers are not sure if TPS or ECM reflash are actual fix Here is a link to the TSB

https://www.kiatechinfo.com/TechnicalInformation/local_viewer/Default.asp?title_num=331&toc_type=GROUP&menu_type=1_4

[8ftsq]

Sorry about the link....

TSB ENGO44r

[sandt38]

Could be way off base here but..... when you replaced TPS, did you reflash ECM with latest software? I would not go any farther until you have done this. I work for Hyundai and have done similiar procedures on Sonatas. In my estimation, engineers are not sure if TPS or ECM reflash are actual fix Here is a link to the TSB

https://www.kiatechinfo.com/Technica...&menu_type=1_4

I did not, but the car is long since fixed and gone. IIRC this model was just outside the reflash, but I might be mistaken. I have had to do this on one or 2 other Hyundai/Kias, so I am not terribly unfamiliar with the reflash.