high rev (3000 RPM) problem...seeking advice.thanks

[tat2lu]

i have a problem with my 97 infiniti qx4.i had it put in the computer and the only thing its reading is missfire. but the truck stays stuck on a high rev at about 3000 rpm when the truck warm up.they say its a tune up that it needs and i changed spark plugs,pcv valve,air filter,oil change and iam still having this problem ...can someone please give me some advice on what it is .....the only other thing i can think of thats its a throttle problem.

also the ckeck engine light is now on.

also the code that it was reading was p300

[Q45tech]

Each sensor is tested by ecu in that it's voltage is appropriate [+-20%] for rpm.

Could be a massive vacuum leak [hose] or a stuck IAC valve? Why one visits technicans every 90 days to allow them to maintain in perfect condition. If your standards are lower even 180 days [twice per year] can maintain a functioning vehicle--- usually.

There are significant differences between a generic mechanic and a Nissan expert technican...................one who sees thes vehicles on a daily basis.

Ignition coils might have been damaged when plug were changed is also a factor. 11 years is a good long life on OBD2 vehicles.

[Q451990]

also the code that it was reading was p300

P0300 = Multiple Cylinder Misfire