So I replaced my timing belt and water pump yesterday and everything looks good but for some reason when the car is warmed up it idles at 1200. Only when it's hot outside tho.. Once it cools down it goes back down to 700-800 like normal. Any ideas?? Could it be the timing belt and am I damaging anything driving around at 1200 rpm? Other than using more fuel

 

As long as you set cylinder 1 to top dead center when you aligned the timing marks the belt should be ok, if your timing was off you'd have known it as soon as you started the car, it would have ran rough. The more the timing was off the worse it would have ran. Any codes? I'm thinking the intake air temp sensor is starting to go, but unfortunately that's paired with the MAF. Test it or have it tested first, it's done with a blow dryer and ohmmeter to check resistance going through the sensor wire.

 

No codes so far. I think it's been a coincidence that it only happens when it's hot outside.. But it for sure happens when I'm in stop and go traffic. Am I doing any damage to the engine? I hear the MAF sensor is quite pricey.. I sure hope it's not.

 

I doubt you're doing any harm to the motor, if you have an automatic trans. you are putting a bit of strain on it when you shift from park to reverse or drive if it's idling at 1200 rpm. The MAF is $230 that's why you don't just want to replace it and not test it first. Another possibility(and cheaper) is the coolant temp sensor may be failing, that'll cause idle issues as well. When you accellerate from a stop does the car jerk a bit or does it take a second for the torque converter to lock up at all when you hit the gas? If so I'd say the MAP is going(and a failing MAP can cause idle issues too), that's also much cheaper than the MAF, rockauto has them for $100-$150.

 

If it idles normally when the motor is cold and starts to act up once the motor warms up I'd say it's definitely the coolant temp sensor, a lot of GM's do the exact same thing. The sensor is pretty cheap, it's around $40. If you do wind up replacing it just make sure the new one has sealant on the threads(it should). If not buy a tube of permatex liquid thread sealant and put a bit on the threads before you install it or it may leak.

 

It's a manual transmission and it doesn't jerk or anything when I accelerate. I will test the MAF sensor as soon as I get off work. I also read that cleaning the throttle body and idle air control valve will help. I cleaned it so hopefully it resolves the issue. Thanks for replying guys

 

I doubt it's a sensor issue, think about what was done. More than likely its related to that, if it wasn't doing it before and is now. Check your vacuum lines, a vacuum leak will cause high idle. Then I would check to make sure all of your sensors are hooked up. If all that is good then I would start looking for a failed sensor. Could be a coincidence that a sensor just happened to fail at the same time you did your mod but doubtful.

 

Also if you cleaned the Throttle body check out this post. There is a special film that seals the throttle plate. If you used solvents you more than likely cleaned that film out. Which in turn would allow for air to leak by your throttle plate and cause a high idle.

https://www.evolutionm.net/forums/ev...e-sealing.html

 

Holy **** dude this has been covered 40 million times before. It's the throttle cable. SEARCH

 

Hahahahahahahah

 

I don't check this message board much because most posts on here are people asking, "hey i have a 5.0 out of an 86 mustang, can i swap it in to my lancer and make it AWD? i have $75 to spend"

The rest of the posts are people asking "My idle is high when it's hot out"

You don't even need to use the search function, because there's normally a recent enough high idle/throttle cable thread that you can just scroll down!