I made a post a couple of weeks ago about my truck acting up. Basically when I would shift into neutral the RPM's wouldn't always drop and sometimes they would continue climbing. I cleaned and then replaced the IAC which helped. It no longer continued to accelerate after being put in neutral but if still in gear with the my foot off the gas it doesn't always start slowing down either. Also when in neutral it idles around 1k instead of 600 rpm's like it used to. So I did some more research on here and ended up replacing the TPS. Basically that didn't change anything and now I don't really know what it could be. Does anybody have any ideas before I have to take it in to get looked at?

 

is your CEL on by chance?

 

if its idling around 1000 rpms that's good. 600 is way to low. IAC can make idle too high and too low. i would stall out at 600. i'm surprised yours did not.

not sure about the other stuff.

 

mine idles right around 750-1000

 

Gotta luv it!

Since you done the other, could be DPFE, or EGR valve and/or hose.....

With these computerized & sensored to death vehicles of today, way too many possibilities.

You can replacin stuff for numerous $$$ before you hit the right problem.

IMO, spend the hour diag fee & find it out the first time.

 

Same

 

I did get a code P1506 before I replaced the IAC. After a couples days it went away though. Right now it idles between 1000-1100k. It used to be somewhere between 600-800 and never felt like it would stall. I forgot to mention my truck is a 2001 with a 2.5l.

 

Disconnect the battery and then turn the headlight **** on for like 10 seconds and reconnect it, might fix it

 

Worth trying. Cross my fingers its that easy!

 

Well disconnecting the battery and leaving the lights on didn't fix it. Like I said earlier the CEL went away on its own before and today it came back on. i don't have time to get it read before I go to work but I'm assuming it will be P1506 again since my truck is still acting the same way. When I shift into neutral when coming up to a stop the truck stays revving around 1500 rpm's. When I actually make a complete stop it will drop down to 1k. This is really bugging me and I'm hoping I can figure out what it is without taking it in because I know I'm going to have to shell out some money for some transmission work here soon too.

 

sounds like a vacuum leak, get some starter fluid and spray it around your vacuum lines and intake manifold with the engine running when the rpm goes up you found your leak. You can do the same with carb cleaner just listen for a drop in rpm. Starter fluid works better but it can be deceiving if you use to much and also dangerous if your engine is hot so be careful. You said you replace the IAC did you clean out the ports in the intake and throttle body when you replaced it?

 

Yes I cleaned the throttle body real well when I had it off.

 

It a vacuum leak....clean your mass air also.

 

My truck is doing the exact same thing ive replaced the iac and the tps and the cel came on just the other day and it said it was running lean on one of the cylinders. I cleaned my maf and K&N and its still doing it. I push in the clutch and while the truck is moving the rpms bounce between 1500 and 2000 and then when I stop the engine rpms drop to 1000 but thats still higher than it used to be. Its really tearing up my gas mileage too since its mostly city driving in Pittsburgh. So did you find out if it was a vacuum leak cause I really want this problem gone. Oh yes and my trucks the 3.0

 

Get the codes pulled. Even if you have no CEL.and post them .

 

my trucks code is p0174 and it came on when i first started the truck then i cleared it and it came back on last friday as i shifted into third and got on it a bit to pass someone and that is bank 2 running lean

 

Put a vacuum gage on it and let us know what it is reading at idle, and when you push the clutch in. Do you have cruise control?

 

I do have cruise control yes and where would I go about getting the vacuum gauge and go about hooking it up?

 

Look for a vacuum line between the throttle plate and intake. This is port vacuum. Pretty much any 3/16" or 1/4" vacuum line will do.
At idle you should read a little over 17" hg. on the gauge. If the gauge reads and stays steady no needle jumping your internal engine is good i.e. valve guides valve seals and seats are good if the needle jumps around then I would suspect one of these.
As you open the throttle body to rev the engine your vacuum will drop and when you close the throttle plate you should see a spike in vacuum then settle back to around 17hg.
Step on your break and watch the gauge if the vacuum drops you could have a bad cruise control vacuum switch, a bad break booster or brake booster check valve.

 

Well I figured I would screw around tonight and switched the iac around. Cleaned out the original and put it on. It idled fantastically just like it used to except the fact that it was howling something fierce while it was running. I figured ok well the idle at least is correct so I swapped on the first new one. Idle went to the same as before so came back unhooked the battery and let it reset then still the same so went back to advanced and picked up a second on the replacement plan that comes with them and put new one number 2 on. Still idling incorrectly and after looking inside of the iac's all of them are different. So it comes down to I believe the ones I am getting are either (a) the incorrect ones, or (b) there is a manufacturing flaw where it does not read to the computer correctly. Anyone else have an idea. Or at least get one that actually works correctly. The whole thing is pretty frustrating.