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Discussion Starter #1
I've searched the forums and found lots of rough idle and low idle problems but no fast idle problems. So here goes?

For about 6 months now my 98 Sport would randomly rev up to about 1500 then on up to 2500 rpms when I pushed the clutch in. When it would start doing this, I could shut it off, restart it and it would be ok for an hour or so and then it would do it again. Each time it did this, I'd remove the IAC and clean it and it would go back to normal for a few months. So yesterday it did it and cleaning didn't help. I had to unhook the IAC and hold my foot on the accelerator to get it home. I replaced the IAC and all seemed ok until this morning, and it does it again! Anybody got any ideas? I've been all over it looking for vacuum leaks and even ran the starting fluid test... I can't find a vac leak anywhere. I've replaced the MAF, TPS, plugs and wires in the last 2 years. HELP! :(
 

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Discussion Starter #3
Yes, I sprayed starting fluid all around the intake trying to get some kind of response from the engine, but nothing... I can't imagine that an intake leak would affect it randomly though. Seems like it would cause a problem all the time.
 

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inspect PCV line and replace the PCV valve, roughly $6 at any auto store, just make sure you get the right one as there were different variations, if you do a search there's a thread with pictures of each setup
 

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jeff518 said:
inspect PCV line and replace the PCV valve, roughly $6 at any auto store, just make sure you get the right one as there were different variations, if you do a search there's a thread with pictures of each setup
+1
 

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Thanks guys. I checked the pcv valve and it is not stuck, the ball rattles and I cleaned it for good measure. I will change it though. Interestingly, when I bought this car 2 years ago, the plastic pcv line was broke so I replaced it with a rubber hose. The idle has always been funky, just not this bad. Do you think the "rigged" pcv line could be my problem? There are no leaks in it anywhere that I can find.
 

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I had a similar problem with my '88 Pony once. I replaced the ECU and solved the problem, but that may or may not be your problem. It might be worth a try if you can pick one up a JY cheap.
 

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crimp111 said:
Thanks guys. I checked the pcv valve and it is not stuck, the ball rattles and I cleaned it for good measure. I will change it though. Interestingly, when I bought this car 2 years ago, the plastic pcv line was broke so I replaced it with a rubber hose. The idle has always been funky, just not this bad. Do you think the "rigged" pcv line could be my problem? There are no leaks in it anywhere that I can find.
no, but the PCV itself could still be bad. the ball "rattling" is not a guarantee that it's good.
 

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Discussion Starter #9
pextor said:
crimp111 said:
Thanks guys. I checked the pcv valve and it is not stuck, the ball rattles and I cleaned it for good measure. I will change it though. Interestingly, when I bought this car 2 years ago, the plastic pcv line was broke so I replaced it with a rubber hose. The idle has always been funky, just not this bad. Do you think the "rigged" pcv line could be my problem? There are no leaks in it anywhere that I can find.
no, but the PCV itself could still be bad. the ball "rattling" is not a guarantee that it's good.
Ok thanks, I'll replace it.
 

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Discussion Starter #10
FordMan59 said:
I had a similar problem with my '88 Pony once. I replaced the ECU and solved the problem, but that may or may not be your problem. It might be worth a try if you can pick one up a JY cheap.
Yeah, I thought about that also. If the pcv valve doesn't fix it, I'd like to connect a voltmeter to it, get the normal voltages and then check it when it acts up. Can someone explain how the IAC actually works?
 

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I'm just posting here because I have the same problem with my 97 escort, only since mine is an automatic, it'll occasionally idle at 1500 RPM while in drive and 2000+ while in park/neutral.

I do already have a new ECM for the car which I bought years ago but never ended up needing. If thats the only possible solution I could try swapping that in and see what happens.
 

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Discussion Starter #12
Well, I'm not sure mine is an ECM problem now. I ran a couple of wires from my IAC into the inside of the car and hooked a voltmeter to it. Of course, as murphy's law would have it, it has ran flawlessly for the past 4 days. But this morning it did jump up to 1500 rpms. When it's running normal it will be anywhere from 4 to 4.4 volts, but when it jumped up to 1500 the voltage dropped to 3.3 volts so the ECM was trying to bring the revs down. The lower the voltage the less air the IAC is allowing to bypass the throttle, hence lowering the rpms. I haven't tried the PCV yet, as jeff518 and pextor suggested but I plan on doing that this week. I'd be interested in what your results are if you do decide to change it.
 

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Discussion Starter #13
I'm wondering if this may be a timing issue. I've also had a problem with pinging, which once I press the gas to the floor goes away completely. The car will ping louder, studder a little and then take off with no more pinging for a day or 2. Anyone have any insight on how the timing works on this car?
 
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