High Idle, Around 1500 RPM. Any Ideas????

6231 Views 22 Replies 6 Participants Last post by tiresmoker, Oct 26, 2005

zeteckatt

Discussion Starter · Oct 24, 2005

I have an unusually high idle. When I turn my A/C compressor off it rises to around 1500 rpms. Every now and then it will sit at around 1250 but for the majority of the time, it is at 1500. I checked my throttle body. Checked the idle set screw and it still does it. What gets me is that it will go to 1000 (Correct RPM) when the AC is turned on. As soon as you turn it off, back up to 1500 is where it goes. Anyone have any ideas about this. My zetec has been such a good engine and this is my first problem. It is also a problem because it seems a little harder to start my car now. I have 110K miles on it. I also have a 2000 Mercury Cougar. But I'm still all zetec! Thanks for any responses

1 - 20 of 23 Posts

buzzbomb

· #2 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

1000 RPM seems like a high idle for a stock engine anyway. If it's a stock throttle body, the idle set screw shouldn't even be adjustable. Try resetting the ECU by unhooking the negative battery terminal for a couple minutes, and see if it'll relearn the correct idle.

zeteckatt

Discussion Starter · #3 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

I forgot to mention. I did unhook the battery to reset the ecu. I had the battery off for about 3 hours. Still does the same thing. My car has always had an idle of 1000. Ever since it was new. I'm starting to think it may be a clogged pcv valve or a bad IACV. I don't want to go out and spend a fortune and not have the problem solved. Just had a hurricane here in louisiana so money is very tight for me now. Hoping one of you guys had the problem and resolved it. Thanks

buzzbomb

· #4 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

I don't think the PCV would cause an idle problem, but they're only like $3, replace it anyway. The IAC valve could be the culprit, along with the TPS. Do you have any engine mods at all?

BrokenSVT

· #5 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

The PCV valve comes to mind for me, as does the IAC valve.

zeteckatt

Discussion Starter · #6 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

Yeah, I agree with you guys. I'd just hate to take a chance and spend money on something that may not fix it.

But yeah, Everything is stock except for the exhaust. I have a siliencer in it so I do believe there is more than enough back pressure. So I'd say it's all stock.

zeteckatt

Discussion Starter · #7 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

So do you guys think it could be the throttle position sensor or would or more likely be the Idle air control valve. I'm just wondering why the AC brings it back down to 1k rpm's but as soon as you turn it off it jumps way up. Thanks

BrokenSVT

· #8 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

AC works the engine, so it drives Revs down, just like on the freeway.

ScaldedApe

· #9 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

IAC or TPS. unsplug the MAFS and the TPS one at a time to rule them out. If nothing happens when you unplug both then it's the IAC

tiresmoker

· #10 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

or you could just unplug the IAC and see if that changes the rpms, if it doesn't then you found your culprit.

Have you noticed any climbing revs while at idle? Say like the revs will gradually increase untill the clutch is released or "pumped". Do you have an aftermarket throttle body?

I would unplug the iac, and if that doesn't change anything then unplug the tps. If still nothing start checking for vacuum leaks.

chewbacca

· #11 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

these are the exact same problems i'm having with my car for the last three weeks, when you drive do you notice a sort of chugging or surging when you let off the throttle in like 4 gear and coast??

zeteckatt

Discussion Starter · #12 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

RPM's remain constant at idle. No chugging while coasting or while changing gears. Just a idle that is confused and seems to be set at 1500 rpm's. Can you tell me where the IAC valve is located. I took the air cleaner box off the my throttle body yesterday and did not see any kind of iac valve. I did see the tps valve. So if you could describe where it is and what it looks like, that would be awesome! Thanks

chewbacca

· #13 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

from what i understand the IAC is between the intake mani. and the block where the intake drops down (i.e. PITA to get to!!!)

the tps is just a potentiometer which reads variances in voltage to tell the computer where the throttle blade is located, not a valve.

zeteckatt

Discussion Starter · #14 · Oct 24, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

Okay, I disconnected the IAC valve and nothing different happened. All that happened is that my check engine light came on when i disconnected it. I then plugged it back in and tried to disconnect the throttle position sensor. Didn't see any type of dramatic change. So now im stumped. Do we have an egr valve? Maybe i should try that. If we do have one could anyone tell me where it is located? Thanks !

tiresmoker

· #15 · Oct 25, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

The egr valve, if you have a zetec, is right behind the coil pack and looks lie a little ufo with a vacuum line comming out the top.

If you unpluged the IAC and the rpms did not change, then I would think your IAC is stuck open. You may have a carbon build up on it and it's causing the valve to stay open. It's a pain to get to, mine stuck on me and I took it off and cleaned it real good with some carb cleaner. I let it sit for a day and put it back on, she ran like new.

Did your cel stay on after you plugged the IAC back in?

chewbacca

· #16 · Oct 25, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

i went out and unplugged my IAC tonight with the car running and nothing happened, should the idle have changed with the IAC unplugged??

sorry to post jack, but it seems we are having the same problems.

zeteckatt

Discussion Starter · #17 · Oct 25, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

When I plugged it back in and unhooked my battery to clear the CEL it has not come back on yet. That is with about 50 miles of driving. Could you explain exactly how you cleaned your IAC. The more details the better. I'm going to try that this weekend. Autozone wants $90 for a new one and i'd like to try and clean it before i buy a new one. Also, is there a spring inside i have to be concerned about when i remove it.

tiresmoker

· #18 · Oct 25, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

I just took it off the intake mani and put it in a shallow dish and soaked the crap out of it with carb cleaner.(NOT THE ELECTRICAL) Once you have it off, put in a shallow dish or bowl and spray an bunch of carb cleaner down into the valve, through the holes in the flange, and let it sit for little bit. You can even cove the hole and shake it up a bit. Dump old cleaner out, repeat until clean.(gonna have to do it a couple times) You're basically trying to get the carbon build up off the valve so that it can open and close properly.

Once you have as much carbon deposit off as possible, when the cleaner starts comming out not dirty, soak it real good one last time, shake it up, dump out the cleaner and let it air dry for a couple hours. I let mine sit overnight just to make sure it was dry. It wouldn't hurt to blow some air, canned or compressed, into the IAC to get the cleaner out.

If you can get to the IAC in a position to hit it, try hitting the solenoid to see if you can knock it loose. (much like you would smack a starter solenoid with a hammer)
It is a true bitch to get at though, so you may not be able to get a good whack on it unless you're under the car.

When you disconnect the IAC, if the IAC is functioning properly then the idle should change. If it doesn't then that probibly means that the IAC is stuck.

Have either of you got a cel for a high idle, say like a P1506, or any other code, anything that may trace back to the IAC, just curious.

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zeteckatt

Discussion Starter · #19 · Oct 26, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

I haven't had any cel's as of yet. I wish one would just come on so I'd know what the problem is. It is driving me nuts. I can't work on my car until the weekend due to work. So yeah, I was loving the zetec until now.

I do have another question for ya. Think I could get by without pulling the entire intake manifold. I just don't have the time to do it. What if I were to spray the IAC down really good a few times and blow all excess out. Then possibly spray some cleaner in the port on which the IAC sits. Think that would help any, or would you recommend pulling the entire manifold. Thanks

chewbacca

· #20 · Oct 26, 2005

Re: High Idle, Around 1500 RPM. Any Ideas?

how difficult is it to remove the IAC?? do you have to go in from the bottom? cus i can barely get my fat hands in there to take the wire off??

i too haven't had a single cel since this started happening and i've driven about 600miles so far.

1 - 20 of 23 Posts

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