Idle Comes Down With Clutch Pedal Depressed???

erniet17 · Dec 29, 2013

Is it normal for the idle to come down about 150 RPMs when depressing the clutch and the tranny in neutral?

Thanks in advance!

mikestang63 · Dec 29, 2013

Nope . Run the codes. Most likley your IAC, TPS or MAF

Dave2000GT · Dec 30, 2013

erniet17 said:
Is it normal for the idle to come down about 150 RPMs when depressing the clutch and the tranny in neutral?

Thanks in advance!

That is perfectly normal when your neutral gear switch is broken.
Try to run the codes, and I bet you can't get the engine running codes unless you hold in the clutch the entire time. You can replace it.. or just do what I did and short the wires going to it, tricks it into thinking it's always in neutral and fixes the idle issue. Haven't had any adverse effects yet...

erniet17 · Dec 30, 2013

I did replace the clutch switch with a parts store one a few months ago. I have a brand new Motorcraft TPS that I still need to install but the weather has been terrible.

I believe you have to keep the clutch down during the KOER test??? Although I have bypassed it in the past but I'm trying to get everything to work a it should.

Mustang5L5 · Dec 30, 2013

Run the codes. That should give you a hint as to the issue. Right now, we are just guessing.

It is possible to run the codes without holding the clutch down. However, you should hold it down to eliminate the code 67.

erniet17 · Feb 15, 2014

Ok, didn't mean to disappear but my car was without a fuel pump for a month. It's now back up and running. I replaced the TPS with a new OEM one and the idle still drops when I press the clutch.

erniet17 · Oct 15, 2014

Still having this problem. I have gone through the whole Surging Idle Checklist and still have had no luck. Any ideas??

hoopty5.0 · Oct 16, 2014

So... you get a code 11 when you dump codes?

jrichker · Oct 16, 2014

erniet17 said:
Still having this problem. I have gone through the whole Surging Idle Checklist and still have had no luck. Any ideas??

Did you just read though it or actually do it step by step?

erniet17 · Oct 16, 2014

hoopty5.0 said:
So... you get a code 11 when you dump codes?

I only get the codes regarding the smog stuff that has been removed for years.

erniet17 · Oct 16, 2014

jrichker said:
Did you just read though it or actually do it step by step?

I printed it out and took it outside with me and went down the list.

jrichker · Oct 16, 2014

Did you do the TPS setting and testing? Check the TPS base setting and then advance the throttle and watch TPS voltage steadily increase?
Have you checked and cleaned the 10 pin connector pins?

Have you cleaned the IAC using a Gunk or Berryman soak type cleaner and then set the base idle according to the instructions in the second post?

erniet17 · Oct 16, 2014

jrichker said:
Did you do the TPS setting and testing? Check the TPS base setting and then advance the throttle and watch TPS voltage steadily increase?
Have you checked and cleaned the 10 pin connector pins?

Have you cleaned the IAC using a Gunk or Berryman soak type cleaner and then set the base idle according to the instructions in the second post?

The old TPS was good and I replaced it with a new Motorcraft anyways. I tested that one as well and it is good. I have cleaned the 10 pin connectors and put dielectric grease on them. I let the IAC soak and I even used my friends IAC from his car. No improvements.

One thing I noticed recently was that I had a lot of sucking through my oil fill neck. If I would turn off my engine, and then take off the oil fill cap, it sounded like I was opening a can of beer. I have a TFS fill neck and I didn't have the nipple hooked up to the throttle body. I installed the nipple and hose and the sucking is gone.

Can that be an indication of a bad lower intake gasket? I have sprayed about 4 cans of brake cleaner and not noticed any changes.

jrichker · Oct 16, 2014

erniet17 said:
Can that be an indication of a bad lower intake gasket? I have sprayed about 4 cans of brake cleaner and not noticed any changes.

Put a vacuum gauge on the engine. You should see 16"-18" of vacuum at idle.

erniet17 · Oct 16, 2014

jrichker said:
Put a vacuum gauge on the engine. You should see 16"-18" of vacuum at idle.

I did that a while back but I honestly do not remember what the numbers were. It was somewhere around 14-16 and the needle was pretty steady. The short block has a ton of miles on it and was turbo'd at one point. It still runs great but not sure if that would affect the vacuum.

I don't have a gauge but I can get one within a couple of days and I'll post up the numbers.

erniet17 · Oct 18, 2014

I'm just gonna pull the intake off and check those gaskets. I used the 1250s that most people have problems with although I have not had any issues in the past that I'm aware of.

jrichker · Oct 18, 2014

erniet17 said:
I'm just gonna pull the intake off and check those gaskets. I used the 1250s that most people have problems with although I have not had any issues in the past that I'm aware of.

Test, Diagnose and Think - TDT -it saves time labor and money in the long run.

It also eliminates the problems created when something you needlessly swapped causes more problems.

erniet17 · Oct 18, 2014

jrichker said:
Test, Diagnose and Think - TDT -it saves time labor and money in the long run.

It also eliminates the problems created when something you needlessly swapped causes more problems.

I agree, I just don't know what else to check or change out. I've been having this problem for months now and I have checked every connection and setting. It idles at about 1100-1200 and then comes down to about 950 with the clutch in. It drops a bit more with the a/c on. My gas mileage is horrible too. That's why I'm leaning towards a vacuum leak and I've checked every vacuum line and sprayed several cans of brake cleaner.

7991LXnSHO · Oct 20, 2014

@Dave2000GT I hope I misunderstand what you did. Bypassing the neutral safety starter interrupt switch will cause a nasty surprise sometime when your wife or kid starts it in gear. I hope you have styrofoam filled boxes in front of where you park.

erniet17 · Oct 20, 2014

I bypassed it temporarily while troubleshooting. Although my wife and kid don't come near the car, I reconnected it cause I like to have things function as they should. At least most things.

Idle Comes Down With Clutch Pedal Depressed???

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