Engine revs when I press the clutch

[David Findley]

(edited first post to be more specific about the problem)

(First I’d like to say ‘wow, thank you so much! Your website and tutorials are so great — it looks like, as I get into auto mechanics over the next few years, yours will be the first and primary resource for instruction and information. This stuff looks amazing!)

2000 ford focus zx3

yesterday while driving home from some chores, in city traffic, the engine started revving really high as I pressed the clutch in — up to 4k or so RPMs. The revving would go back to normal as I let my foot off the clutch and hit the gas to accelerate again. The problem lasted the short 2 minutes before I got home and parked the car. Haven’t driven it since.

based on some little research, I have three ideas:

1) the clutch mechanism/cable is somehow stuck or intertwined with the accelerator mechanism/clutch

2) IAC is weird

3) vacuum leak

——

(2) and (3) because they are related air intake that might cause an engine to rev, (and because those were suggestions to this problem on Yahoo Answers) but I doubt because the RPMs go UP instead of down, and only when press the clutch.

These peculiar symptoms want me to think that there is (1) a mechanical tie up between the clutch mechanism/cable and the accelerator mechanism/cable in the (pedal assembly?).

anyways, I’m going to continue to research the problem before I actually go take a look at my car. Any comments or suggestions are very welcome !

again, thanks so much !

Topic

[dan]

if the Ford Focus has a mechanical clutch mechanism many cars these days have hydraulic clutches that pretty much use break fluid, the likely hood the throttle is getting inter tangled with your clutch is very slim, does it rev when the car is rolling or when you press in the clutch at a stand still?

could be a vacuum leak, could be a IAC issue

do you have a engine light, any codes?

[college man]

Here is a link to help you.

http://www.ericthecarguy.com/faq/solving-automotive-idle-problems

[David Findley]

Thanks College Man — I’m a little bit excited to be reading through it now, learning my way around.

No, no engine light — which makes me assume that there is less likelihood that it is either the IAC or any other sensor or computer problem. (Though I may be wrong.)

Yes, it is a hydraulic clutch. So, I’ll have to consider your point that the likelihood of an intertwined cable is very slim. When I go out there, I will have to give that diagnosis a closer investigation.

I’ll post updates as I make any advancements. Thanks!

[David Findley]

Ok,

I ran the diagnostics for AIC function:

started the car, which revved to about 1300-1400, dropped to 1000-100 at idle;

turned on lights, radio, A/C to max, power steering — the idle would drop to 900. I pressed the clutch in and out several times, and there was no change. (which rules out a -complete- entanglement between the clutch mechanism and the accelerator/throttle mechanisms.)

There is no audible hissing sound from air/vacuum leak in the engine under the hood when I run the car. It sounds perfect.

So now I am assuming that AIC valve is starting to go, and will buy a new one (and hopefully replace it myself!) on the 1st.

I’ll post a final update if this fixes the problem, or otherwise continue to update the thread as I work the problem out.

Thanks : )

[spelunkerd]

I think it’s a little early to be replacing a part, especially when your vehicle computer hasn’t even identified it as a problem. I would be looking for more evidence before spending money to replace a possibly normal part. I do understand the bind people are in, not having equipment or training to fix something and hoping to get by without professional help. But the pathway of replacing likely parts without investigation can be expensive and fruitless.

The first thing I would do is put it on a code scanner and look at live data, including IAC counts, fuel trim, rpm, etc. An autoparts store may offer a discount version of that for free. By the way,the last vehicle that had similar symptoms of surging idle in my shop showed a coolant temp sensor code, but it wasn’t that, either. He had an occult coolant leak, which caused coolant to incompletely bathe the coolant sensor, which gave spurious data, which caused the engine to ask for more fuel. When you find the root cause, all the secondary problems disappear.

[Joe]

just to be clear… with the car in neutral and the engine running you press in the clutch. Does the engine rev up?

[David Findley]

: O !!!

Have to start learning somewhere. Worst case scenario, I have a new AIC valve.

Dang computers making things difficult. As soon as I get a manual, I will have to see if I can’t inspect all the computer and sensor parts. I’ll also make sure to look for leaks — even super small ones. Thanks for reinforcing the idea that auto mechanics are not a simple task.

quicknpainless, no, no the engine did not rev when I pushed the clutch in, (which made me retract my original idea that there might be a binding or entanglement or something.)

Maybe a good question would be: how do you know if the AIC valve is dirty or needs replacement, just by looking at the part itself? Would a caked grime make itself apparent enough?

: D

[Joe]

http://www.ehow.com/list_6046295_signs-idle-air-control-sensor.html

[David Findley]

*I was really low on gas when it happened. I put some gas in it and drove around today without any problems except an idle ~750.

I realized that, for the same reason a vacuum leak could cause the engine to rev, dirty fuel injectors might be the problem. I’ll have to put a concentrated amount of injector cleaner in my gas tank and see if that helps the problem.

I may see if I can’t inspect the fuel injectors themselves, (if I have the tools to do it.)

I’ll post an update if I fix the issue.

[aze a]

what was the problem? i have the same problem

[Aaron Anderson]

I had this same problem. Ended up being a hole in the vacuum line. however the vacuum line is crimped on and hard to get something in there to cut it off. I had to cut a vacuum line down the middle and use two hose clamps to patch it as a temporary fix.

[Author]

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