uneven idle

When idling at a stop my truck's RPMs for some reason will jump at least 500 RPM. Am i tripping over nothing? Usually the only thing on is my radio. Nothings really drawing significant power.

 

Make sure the AC is off and the zone selector switch is not on ANY of the windshield positions (put it on face or feet). The two windshield modes use the AC to dry the air so if the AC is cycling a little that would bump your RPMs.

 

i'll try that. its always done it. regardless of the AC, which is usually off.

 

Bad plugs or a gunked up MAF sensor or IAC valve.

 

eh, I just noticed you have a 99. Might need a tune up being almost 10yrs old. My Corolla idled high until I poured some Seafoam through it. Was idling around 1300RPM when it should have been around 700. Plugs and wires might help. I had iridiums in mine so they should still have a lot of miles left on them.

 

not that i trust dealerships but it is certified used, ill check and see if it has new plugs and such. The dealership did do a lot of work on it before i bought it. but I just took it in yesterday and the bastards found nothing. GO figure.

Peircedtiger: what is seafoam?

 

Seafoam is a cleaner. You can get it at Autozone, Advance Auto, Pep Boys, etc. Pour it in the gas, in the oil, and through a vacuum line on the intake. It cleans up the build up in the engine. I like it since it's equivalent to those 3-step fuel system cleaners the dealerships, Jiffy Lube, etc offer. Only they charge $70-$100 and Seafoam is $7/can.

My Corolla was a "Certified Used", but there were still a few things wrong with it. And it still isn't remotely equal to "new" regardless of the warranty they put on it. The longer warranty is probably just to get people to buy someone else's problem (what I consider all used cars nows).

If you have a scangauge you could monitor it for trouble codes too. Even if the light isn't on.

 

I actually think my friend has something to check the codes. Ill ask. Ill also check out that seafoam stuff. Plugs and such are new

~THanks for the input guys.

 

You're welcome! Probably get two cans of seafoam. They say X number of ounces per gallon of gas, per quart of oil, etc... I hate measuring stuff. I just put half in the gas, part in the oil and the rest down the intake. Oil might not be needed, and might not be a good idea. My car started leaking or using more oil after that. An older engine like that might be worn and cleaning out some of the crap in the oil might make it use more oil (buildup acting as seals, then dissolving from the seafoam).

I'd put it in the gas and intake first to clean out injectors and intake system. If that does help, maybe add some to the oil shortly before doing the next change.

When you put it in the intake have the engine running and keep a hand on the throttle (or have someone rev the pedal) to keep it from stalling. I usually pour a good amount in (just guess, it may take more or less depending on how dirty the engine is), and then turn it off for around 5 minutes (or one beer). Start it back up and watch white smoke pour out the exhaust. Do this some place WELL ventilated! Mine dumped so much smoke I couldn't see my house 20 feet away! While it's running pour a little more in. Maybe repeat the 5 minute wait. I figure this is equivalent to the dealer/quick lube jobs where they pour some in the gas, something in the oil, and a can or bag to the intake and let the car idle for half an hour (until the can/bag is empty). Only Seafoam has different directions. They call for the 5 minute wait time. Probably so the stuff can sit there and dissolve build up. So if you do a combination of the two methods it should clean it out real well.

My car also went from around 27-30mpg up to 37 which is more normal for me (and frankly, it's outstanding for winter gas and a set of studded tires still on!).

 

awesome, ill see if i can pick some up.

 

Just pour it in the intake vacuum line SLOWLY. Start out with a few drops at a time and listen to the engine. You'll see how it starts to bog the engine down. I find it easier to prop the tube up, and use one hand on the throttle (on my car, not the truck. damn fly-by-wire!) while the other pours. Saves having a second person listening to the engine from the cab and trying to catch it.

Also, if you dump a little more in you can rev it up before the liquid hits the engine since you're the one pouring and manning the throttle.