Limp Home Mode and how to get around it - Kia Forum

 
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post #1 of 5 (permalink) Old 06-21-2019, 01:03 AM Thread Starter
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Limp Home Mode and how to get around it

Hello all. 2005 cinco 5spd currently with 211K miles, owner since 2014 at 128k. Original engine, clutch, transmission, CV shafts and suspension so far.

In case you are unaware, our cars have a limp home mode in the programming, which can be triggered for all sorts of reasons, and it causes the car to high idle, rev limit to 2500 rpm in gear and 4000rpm in neutral, which means essentially 50mph top speed. If you try to exceed 2500rpm, it cuts out the engine until 2000rpm is reached, and then allows it to power back on. Very, Very annoying and potentially dangerous on the interstate. I happened to discover LMH due to a cheap ebay MAF. But I wasn't going to pay $200 for quality MAF, especially since the Ebay MAF otherwise runs fine and gets the same MPG. If the car was going to play dirty, so was I.

I installed a $6 quick battery disconnect and I use it once a week to disconnect the battery for only a couple seconds. For some reason the radio presets and clock still retain memory after the disconnect which is pretty cool. I have figured out the circuit and will eventually install a push button in the car to reset only the ECU on the fly. So far 10k miles without a hiccup.


Next project is installing the custom roof rack built from a ford explorer rack. It always annoyed me that these cars never had a factory rack, so I made one. If anyone is interested in that let me know and I will post a how-to.

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post #2 of 5 (permalink) Old 06-21-2019, 08:09 AM
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nice trick, but have you considered a junkyard MAF?
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post #3 of 5 (permalink) Old 06-22-2019, 12:06 AM Thread Starter
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sure have. just not a local pull it with a kia rio in the yard. plus, I already had the ebay maf. bought it a couple years ago when I saw them for $18, and thought the price was too good to pass up, even if I did not need the MAF at that point.
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post #4 of 5 (permalink) Old 06-22-2019, 03:46 PM
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Limp mode is an emergency software protocol used to protect valuable engine components. Why would you want to disable or bypass it when it comes into play. Better to fix what is causing the issue than turning a blind eye....don't you think?
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post #5 of 5 (permalink) Old 06-23-2019, 04:56 PM Thread Starter
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You and I agree more than you might think. I found the underlying problem to the car not running right, and I did fix it...by disabling the LMH feature.

Limp home mode is more concerned about getting the consumer to take the car to a mechanic than it is about protecting the engine.


Lets take the example in this thread: car started to have eratic idle and stumble with aceleration. ECU flags MAF with codes. MAF is testing and fails. MAF is replaced with cheap MAF. Car now runs fine with cheap MAF. normal idle, power, normal MPG, no knock, no stumbling. BUT, cheap MAF gives 'dirty' signal. ECU doesn't like the variation of the signal, and over the time of 2 weeks of normal driving it decides to not 'trust' MAF, and triggers LHM. I take it you are appreciative of this intervention? the ECU took a normal running car and purposely made it run worse, to the point of being nearly unusable to the operator.


The "appropriate" fix in my scenario? buy a more expensive MAF. the cheap MAF works but is not preferred by the ECU. The car itself at 200K miles has residual value in the sub-$1000 range. New part is approx. $200. The problem is most people in this situation will simply junk the car as the economics don't work out. There is a reason there is less and less activity in the 1G Rio forum.
Does junking the car protect vital engine components? Does it extend the life of the car for the owner?Ö
You do what you think is right for you. I'm not here to persuade you away from what you think. I'm giving you all of this information on resetting LMH without intent or purpose. It is up to each person to decide what this information is to them.

I will update you it 4 years when my car reaches 300K miles with the original engine, transmission and clutch. It will have made the last 100K miles without the safety net of LHM, with the cheap ebay MAF. There's a good chance you may have moved onto a different car by then.
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