Hyundai Accent - Random stalls or starts with high RPM & no tach

Maintenance/Repairs
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1

Hi guys.
I have a Hyundai Accent 2012 with 62k miles, 1.6L engine.

I am having an issue, maybe you can give me some clues on what to check tomorrow, i will be doing some maintenance removing and cleaning up the throttle body passage and butterfly with cleaning spray.

The issue i am having is

  1. the car randomly stalls at lights. This is the reason i want to start cleaning the throttle body.
  2. Sometimes when starting the engine, RPMs are high but the tachometer needle does not register anything while the engine vibrates like if it was missing a cylinder. I turn it off, then start again and the car will start absolutely normal showing the RPMs in the tach around steady 800.

RPMs idling is steady, not going up and down and i do not have an issue like sticky accelerator or anything like that.

There is also a clean dashboard, NO check engine light, so i have no error codes to give me a clue about what is causing the issue.

What else should i check while i work on the intake section doing the clean up?

Thank you for any tips.

2

Now those are interesting symptoms…

The “no tach signal” and no CEL makes me think that the crankshaft position sensor is partially bad… although that usually means the engine won’t start. The “partially bad” diagnosis is because of a rough running engine…

What you really need to do is hook up an OBD2 scanner to the car so you can take data when this happens. There is a lot of parameters I’d record just to get an idea of where to start. If you don’t have these tools, or don’t know where or how to look at the parameters, call in a pro.

3 Likes
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Thank you Mustangman.
I cleaned up the throttle body and the problem persisted, so i hooked up a cheap ELM327 bluetooth scanner and found the “PENDING” crankshaft position sensor trouble code. I learned these codes can linger there without showing up in the dashboard’s check engine light, I guess until the part actually completely fails?
I replaced the sensor and voila, problem solved.
Thank you for the tips.

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If a crankshaft position sensor fails, it may not set a check engine light… But the engine will not run!

And it can be intermittent as you well know! Thanks for reporting back with the solution.