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Hey guys, appreciate any input here. I got a jump/surge in my RPMs when I have my foot on the gas and/or when around gear-shifts(automatic). The rpms will jump up and down and occasionally surge upward dramatically about +500rpm for a moment. I get a 0505 IACV fault code.

A bit of perhaps relevant history: when I got the car I had to replace the TPS. The replacement TPS I could only get to calibrate from .5-4.2 instead of the .5-.4.5. It solved the problem and the code went away so I figured good enough.

Then I started getting the IAC fault code. It's been about a month or two and at first I suspected a vacuum leak. I checked and found none. Replaced IAC valve and didn't solve. Now I sometimes get the TPS code again. It's like when I start the car it chooses TPS code or IAC code, then acts accordingly. If TPS code, then there's no rpm jumping - instead I have to go +1000 rpm to shift gears. If the IAC code, then shifts fine but jumping/surging rpms.

I got a PCV to replace but right now I'm just like, wtf? If it were some kind of air problem - how could it just disappear randomly when the TPS code chooses to appear? So now I'm wondering about the TPS calibration. Any advice would be appreciated. 99 Honda Civic LX.

 
Rep Power: 222

I'm guessing you didn't put OEM parts on

 
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Your guess is a good one. I also just got a p1399 code come up with the TPS code yesterday. It wasn't in the manual but I look online and it's apparently some kind of misfire code. So at first I got a TPS code. Replaced TPS and started getting an IAC code. A month later and I'm getting a TPS code again, along with a p1399 misfire code.

I suppose I should fix the misfire issue then get the TPS to exact specifications and see what happens then.

What I really could use is a robot mechanic. That way I could be like, "Also I'm getting px1700 code on my robot..."

 
Rep Power: 222

Go put OEM parts on, go to a junkyard if you don't want to pay the price of new ones