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Discussion Starter #1
so i've read every rough idle thread that's come up here since ive been here (about six weeks) and i have another one.

my car has a somewhat rough idle- in particular, when i open the hood, it looks like the engine is shaking, at least more than it should be. sometimes the idle is whisper quiet and smooth, but most of the time it's noticeably shaky. i took a video on my camera yesterday at the shop but i haven't loaded it yet.

anyway-

when i get to idle at a light and i feel it get rough, i can see the my odometer backlight and the cabin light (if it's on) start to flicker a bit. today, for the second time, it straight died at the light. it started right back up after.

this weekend, i replaced the air filter, fuel filter, PCV valve and changed the oil & filter. the idle is the same (although in driving the car is noticeably smoother). i've also cleaned the TB, run seafoam deep creep and cleaned the MAF

because of the flickering of the lights and the dying (which, if i recall correctly, left the battery light on) is leading me to think electrical- battery or alternator... but records from the PO show the battery is less than a year old. while i was doing the work on saturday i pulled the plugs & wires and the plugs look brand new, and the wires look decent, but maybe it's time for all new plugs/wires. records from the PO show very little outside of oil changes so i'm going through and doing every thing since i don't know when things were fixed.

thanks in advance.
 

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Oh boy... I say an alternator and i am pretty damn sure. The car is trying to stay alive but your alt is in bad condition and it struggles and eventually stalls.

Do you notice engine vibrate when you apply electrical load ?? Such as flashing your high beams, horn... Try turning the dome light and see if it flickers and has a vibration following.

I have the same issue but thank god it is not as bad. Get your alternator tested. I don't think it is that expensive and i am pretty positive that is your problem. Alternator's are very week on foccis and you have a 2000

Just for the record, i tried doing a BIG 3 when i did not know the alt was my problem, but it didn't seem to solve the problem. BIG 3 is adding fat wires instead of your stock grounds + one fat wire from alternator to the battery (that wire is fused)
 

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If the idle drops too low the lights will flicker because the alternator isn't producing enuf power. This doesnt mean the alternator is the problem it just means the car was running too low and the alternator could not produce enuf voltage at that level.

My old 2000 zx3 did this too every now and then and my 2001 zx3 also dips now and then at the lights. I think on the first one it was egr related and on this one im not sure yet. Check for vacuum leaks, pcv hose, what the resistance on your plug wires? how old are your plugs and what is the gap at?
 

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Low idle and flickering lights doesn't mean a bad alternator. A low idle by itself can cause flickering lights due to the reduced alternator output at lower RPMs.

I notice you have a 00 ZX3. Did you check the rear PCV hose? Check this thread:

ZETEC Engine Stumble - Solved!

Page 2 has a picture of the hose and the part number if you need a replacement.
 

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This particular hose doesn't have to have a hole in it to cause problems. Over time the heat radiating from the engine will cause the rubber to deteriorate and lose it's rigidity. Under a vacuum load the hose can simply collapse on itself, thus blocking the vacuum lines and causing your engine to stumble at low RPMs.

I would check this hose and then check other vacuum hoses for similar problems, particularly around the engine. If they are soft they might need replacing.
 

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Discussion Starter #6
NatDogg,

what's funny is i read that thread and i thought i checked the hose. i looked back at the pictures just now (since i didnt have this with me at the shop) and i noticed that i had checked the wrong hose. so i thought i had ruled that out as the cause, but i was wrong.

let me check that out tonight and i'll get back to you. thanks!
 

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I'd also rule out the alternator. If your problem is intermittent, I'd suspect an electrical issue, rather than a vacuum hose.

Fuel injectors can act this way. One may not be opening all the time.....causing a low idle speed (car is running on three cylinders), the engine will shake, the eng may stop, and the battery light will flicker.

When the engine has a coil-on-plug......an intermittently firing coil may have a similar symptom. Although this usually causes a CEL, unlike a sticking injector which may not.
 

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Man... this is so difficult to diagnose then.

If you find the problem and fix it, please post here. I'll be very thankful
 

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Discussion Starter #10
no update yet, i want to bump this back up maybe others have ideas. i havent had time to look into it what with the holidays and now it's just stupid cold out... so this will probably have to wait until next weekend. im going to my garage to install speakers and seal the windshield cowl which i keep forgetting about, and while i'm at it i'll probably look into this- i might just replace the plugs and wires first since god knows when that was last done, but the money has to line up first.
 

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Same symptoms

I'm having the same issue with my 2003 ZX3 - she runs fine for a few days, and then intermittently while driving or at a redlight will stutter where the idle goes high and then drops, battery light comes on and car dies. or she will idle real rough in both park and drive. EGR valve has been replaced, along with fuel filter, and cat. I haven't checked the battery, or alternator yet but my lights do not dim nor have I lost the radio either. Last code was EGR before the replacement. I noticed another thread stating a bad coil pack was causing similar issues. Please post your fix if you resolve this issue. I'm still chasing mine down and its becoming more frequent.

Thanks!
 
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