98 civic ex sedan high idle

[brian86]

I have a 98 civic ex automatic I had cel come on. Notice that when driving car at 45 mph car is running at 2000rpm. 50 mph is at 2500 rpm. And just kept going up from there. Ran scanner and code p0138 o2 circuit high voltage bank 1 sensor 2, P0136 o2 circuit bank 1 sensor 2, P0505 idle air control system. I cleaned the iacv and the p0505 code went away but p0136 and p0138 came back. So I replaced the o2 sensor and I'm still running high rpms but no cEl. If I am sitting at stop light I see that rpm fluctuating and when I'm driving on cruise control it is fluctuating. I have checked for vacuum leaks didn't find any. I'm lost and don't know what to check next.

 

[HeX]

Further explain what you mean by "fluctuating". Is it jumping several hundred RPMs? Do they drop so low that the car feels like it may shut off?

 

[brian86]

I'll set cruise control at 45 which is running at 2000 rpm and while driving you can see it go to 2300 2400 and then jump back down to 2000

 

[brian86]

It doesn't ever feel like it's gonna shut off

 

[dancam]

Downshifting when you go up hills? Or not?
Have you checked your transmission fluid? Have you ever changed it and the filter?


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[brian86]

My sister gave me the car for free it's been sitting since 2013 I just got it up and running I dont down shift on hills dont really drive hills. . It's a automatic I called the parts store and they told me there is no filter to be changed when changing the transmission fluid. I'm gonna try to change the full this week

 

[xxBLOOD88SHOTxx]

Check the vacuum with a vacuum gauge, they are cheap and are very useful.

Make sure you don't have an exhaust leak upstream of the o2 sensors.

 

[brian86]

Idle

 

[brian86]

Wot

 

[xxBLOOD88SHOTxx]

What are you checking? TPS?

 

[brian86]

Yes that was the tps

 

[brian86]

Ok so I messed around with the car today I had air in the system. I am now running 2000rpm at 45 and 2500 rpm at 55 60ish. Is that normal now

 

[xxBLOOD88SHOTxx]

Depends on your gearing and tire size, google it.

 

[dancam]

Ok so I messed around with the car today I had air in the system. I am now running 2000rpm at 45 and 2500 rpm at 55 60ish. Is that normal now

You had air in what system?
Do the rpm's hold steady or still fluctuate?


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[xxBLOOD88SHOTxx]

I don't understand what he means by high rpm, the rpms increase as you go faster...

Rpms @ 50mph will be higher than at 40mph

Autos bounce around a little, especially trying to maintain speed as the torque converter locks up and unlocks etc. It wont stay a constant rpm.

 

[brian86]

I'm sorry I not used to driving cars I'm used to driving trucks to where when you are doing 65 your barely pulling 2k. I'm not used to driving a car and doing 65 and running 200 rpms.

 

[brian86]

Not 200 rpm I mean 2800rpm

 

[xxBLOOD88SHOTxx]

Barely 2k and 2.8k is not a huge difference. You think 2k is high at that MPH, try driving with a b16 or type r trans mission and being at 4k @ 70mph. Trucks have lower gear ratios (highway gears usually) for fuel economy and most of their torque is down low anyway.