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Discussion Starter #1 (Edited)
2011 2.0T
Curious if anyone knows how the tach receives signal?

Out yesterday, just normal driving but noticed that the car wasn't as responsive as usual, no miss, just seemed sluggish and a couple of times a distinct hesitation as if the engine cut out. Had a/c on and the air was only cool, even when on low temp, so down went the windows and opened the sunroof, continued home. Maybe 10 minutes from destination noticed the tach was at zero. Now that explained the a/c, the system didn't recognize the rpm's so compressor was only on minimal displacement, but with no tach I was suprised the car was running. If the signal came from the CKPS (crankshaft position senor) and the sensor was bad, I would assume the car wouldn't run.

Parked the car at the back garage, pulled off cover and looked for something amiss, but nothing. Didn't think the tach problem was fuse related, but checked anyway, good to go.

Started the car and tach worked properly, put cover on and took it for a ride, performance normal and a/c cold as ever. Out to dinner last night, no problems for the 60 mile round trip.
So?
 

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Disclaimer: I have not had the dash/cluster in one of these apart. That said, most analog needle gauges today are stepper motor driven, controlled by the ECU. The engine/CKPS can be working fine and there be an issue with the ECU, wiring or cluster/stepper motor that causes your issue.
 

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Discussion Starter #3
Thanks for the reply. The concerning part was that not only the tach wasn't working, but the engine itself was flat with a couple hiccups,
Ordered a new ckps, actually found a new Kia unit for $22 so I'll give it a try and check out the old one.
Thanks again
No problems today, back to running great.
 

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Discussion Starter #4
Guess I found the answer. Out today, maybe a couple hours in the car, start, stop a few times no problem, but make a turn at a traffic light onto the highway and as usual needed to pass some slower traffic, pressed the gas pedal, car stumbled, felt like it shut off, tach dropped to zero but kept running, now cel on. Pulled off the road shut it off, restarted, tach working, car ran fine for @ a mile then stumbled again but got it home. Read the code and good old P0336 crankshaft position sensor. Guess I'll replace it when the new one come in and see if it was the sensor or something in the circuit.

Thanks everybody
 

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I can sorta relate to that, albeit not my my Optima--recently had to have one replaced on my old MB CLK 55; not a cheap part on these German cars, that's for sure.
 

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Discussion Starter #6
You won't believe the problem. Had installed NGK plugs, recommended by NGK, designed for a Mini Turbo on Friday. After the install car idled fine, but after pulling out of our driveway, the car hesitated, but fine on the way to the restaurant. Coming home, one bad hesitation, then no tach, and A/C cool as ecu not reading rpm's and then, just about home the cel came on, P0336.

Hard to believe after a plug change the CKPS would go south, so Saturday morning put in a new set of Denso 22's I had in the garage and would you believe the car has been fine ever since. Couldn't believe the plugs would cause this problem, so called NGK this morning and NGK Tech couldn't give me a reason, figures a NGK tech couldn't tell me the cause, but did say he has seen ABS lights along with others come on with a plug change. All my years have never seen nor heard of this condition, but have over 250 miles on the car since Denso's installed and it pulls strong, actually seems stronger as the tire(s) lite up easily.
 
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