High RPMs

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2003.5 Titanium Gray MSP
Hello everyone..first post here. About a month or so ago I purchased a 2003.5 MSP with @95,000 miles on it. About a week later, check engine light came on, saying it was the front O2 sensor. I replaced it, a few days later it came back on saying there was an exhause leak. Found out there was on on the manifold, got it fixed. Came back on a few days later saying the cat was bad. The dealership told me it would be the one mounted on the manifold. I took it to the shop I've been taking it to, they said mine didn't have one on the manifold and I just had the 2 in-line ones, they replaced both of those (with bigger piping on them), light hasn't come on since. As far as that, the only thing I've done to it is put in a K&N air filter, and ran a few tanks of 93 octane fuel thru it (the dealership I bought it from filled it up with the cheap stuff, which caused me a couple misfiring problems.) Everything seems fine, but a few days ago it started running high - the RPM's, on cold starts, go straight up to around 1500 (usually it would go that high, then immediately drop down to around 600 or so, which it does now after it's been driven a while), and my cruising RPM's are around 3,000-3,200, whereas before it was around 2500. It is also causing a noticeable increase in the gas consumption. But it's running just fine. I've seen some posts on other places saying the RPMs are fine that high, is it just now getting to that becuase I've fixed some things/got good gas in it, so it's now acting like it should?
If so, any ideas on the gas consumption? I'm taking it on a semi-long trip next week, so I'll know for sure, but it still seems rather high...

Thanks, and sorry the post is so long and possibly not very clear. I'm a electrician, not a mechanic lol
 
well what speed are you driving at. when im going like 80 its usually at 3300 rpms or something
 
well, you fixed an exhaust leak, replaced your primary o2 sensor and replaced both cats. Maybe your ECU is making some minor adjustments to compensate for the changes you made(fixing stuff). I dunno, just guessing
 
^^ Have you tried resetting the ECU after all the changes?

(Taking the negative terminal off of the battery, leave if off for about 15min)
 
My car usually runs better after resetting the ECU, it's a good idea after replacing bad parts or after adding mods.
 
im with the last two posters, and mine does the same thing on cold starts, it will sit at like 1500-2k on idle for a little bit to the engine warms up. but then again ive changed parts(timing belt) and didnt reset the ecu lol.
 
cold starts its normal to have high rpms... every car does it... its apart of the warm up process.. Now if it stayed high at idle even after teh car is warm thats another story...

And if i remember correctly around 70mph im aroudn 3.1k on the tach which is normal in 5th gear.
 
wyvern you are probably right but will it do that no matter the temp outside? i started it today and it was like 80 out and it still ran higher for a bit. but im right where you are at 3100 at 70
 
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