Rough idle - Page 3 - Taurus Car Club of America : Ford Taurus Forum
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post #21 of 58 (permalink) Old 05-06-2012, 01:28 PM
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Sorry to highjack this tread, but I went for emission test last Friday.
The next day when I started car in the morning, it had lumpy idle that went away when engine warmed up. But every time now that I start a car cold, same thing happens - lumpy idle that I could feel through steering wheel and pedals.

It's a '01 Vulcan with 153,000 km (~93,000 miles). I installed brand new Motorcraft plugs and changed wiring (Champion) about 15,000 miles (24,000km) ago. Throttle body is also clean and I cleaned IAC valve last Fall. I tried to unplug a wire from IAC valve, idle become even worse, that means IAC is working.

PCV has not being changed, but it rattles, so, I guess, it's working. Planing to change it at 100K miles (like Ford recommends).

CEL is not on, but previously I had Small EVAP leak, but no vibrations at idle. After resetting the light, car passed e-test the next morning with flying colors!

HC ppm (@ 40km/h): Limit 57, mine 8, (@ Idle): limit 150, mine 7.

CO % (@ 40 km/h): Limit 0.32, mine 0.01, (@ Idle): limit 0.7, mine 0.00.

NO ppm (@ 40km/h): Limit 421, mine 9
.
And the following morning it developed lumpy idle.


Thanks in advance.

Last edited by 01SE; 05-07-2012 at 07:35 PM.
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post #22 of 58 (permalink) Old 05-06-2012, 10:49 PM
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If you just reset the CEL, then the car might need some time to relearn the idle mixture settings when cold. Let it idle in park and drive for 2 minutes each next time you start it cold.

If it's still rough, you should report your long term fuel trims (LTFT) at cold idle (when it's shaking) and hot idle. You might have a vacuum leak or dirty MAF.

It doesn't hurt to check all your vacuum and EGR hoses again after inspection if they were poking around under the hood.

Good emissions numbers. The catalytic convertors these days are very efficient. I remember on Mythbusters they did some testing with a gen 4 Taurus and the emissions numbers beat the newer car! I remember CO came in at zero measured!
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post #23 of 58 (permalink) Old 05-06-2012, 11:19 PM
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Quote:
Originally Posted by 01SE View Post
Could they have knocked some vacuum line during emission test?
That was my first thought.

"Spare the duct tape, spoil the job."
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post #24 of 58 (permalink) Old 05-07-2012, 06:17 PM
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Throw a volt meter on the battery while the engine is running and check that it is between 13V and 15V ... around, not necessarily steady but around there.
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post #25 of 58 (permalink) Old 05-07-2012, 07:42 PM
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Thanks for the answers.

Today did some digging under the hood. Took one by one wires from the coil pack. No spark on the wire leading to the cylinder one. Engine was too hot to try switching wires around or to take a spark plug on cylinder one out.

Car is 11 years old, 95,000 miles, looks like original coil pack. Don't want to just throw money at the problem. What are the chances that car needs a new coil pack? Or is it something else?

Thanks again.

EDIT: Drove around 200 miles since e-test, I think it should be enough to bring CEL on. But CEL is not on.

Last edited by 01SE; 05-07-2012 at 08:09 PM.
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post #26 of 58 (permalink) Old 05-08-2012, 12:12 AM
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If #1 wasn't firing, but the companion cylinder #5 was, then that has to be a bad coil (if you were using a grounded tester). If you were just using the plug wires, then it's possible you have a bad wire or a fouled spark plug that isn't grounding.
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post #27 of 58 (permalink) Old 05-09-2012, 07:09 PM
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Yesterday: Changed around wires, looked at the spark plug in cylinder 1, - looks good (same as the one in cylinder 6). Drove the car, CEL come on. NAPA and 2 other stores refused to read CEL for me for free, so they lost my business. Spoke to the mechanic, he said that he's pretty sure that I need a new coil. Disconnected the battery, replaced coil (old coil had a micro crack). Guess what? Car still misfiring and shakes badly! And I can see fuel gauge needle going down!

Today: Went to the mechanic, he spent just over an hour and could not find anything wrong! Told me to drive around 'till CEL comes on. At least he did not charge me.

I'm at the whits end

Any ideas?
Thanks

Last edited by 01SE; 05-09-2012 at 08:59 PM.
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post #28 of 58 (permalink) Old 05-09-2012, 11:13 PM
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If the coil pack was bad, you would have two dead cylinders. On the Vulcan, the coil pack will send spark to each paired cylinder even on the exhaust stroke. When I bought my '04, i had two dead cylinders that were paired from the pack. Swapped out coil packs with a buddy's and it ran fine. So if you have spark on one but not the other on the pair, I would suspect either a bad wire or plug. If you replace the plugs, spend the money and by the motorcraft plugs. Trust me, it's worth it.

I've been fighting a rough idle for a year now, last night I replaced the lower intake manifold gaskets, the EGR gasket, and the IAC gasket, along with the uppers. So far after about a 50 mile test drive. The idle is rock solid. Granted, since I've own the car I've replaced the coil pack, plugs, wires, MAF, PCV Valve, the gasket at the IMRC, and a known bad O2 Sensor.

For those suffering from flickering headlights at an idle, check the voltage with an volt meter. 13-14v should be the norm. Anything less may indicate the the alternator is on its way out. I recently had my rebuilt, the brushes wear in a very funky manner which will result in destruction of the armature. I would also check the ground at the PCM. When I had mine apart, the ground bolt was very rusted. I cleaned it up and greased it to prevent further corrosion.

Eric
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post #29 of 58 (permalink) Old 05-10-2012, 12:35 AM
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If the coil pack was bad, you would have two dead cylinders.
This is untrue. While loosing both cylinders is one failure mode, a single cylinder failure mode is still possible (I've seen it, and someone on here had a single failure a few days ago). All that has to happen is one end of the secondary winding gets shorted to the grounded side of the primary. It's the same as holding one plug wire directly to the block. The other cylinder on the coil will still fire because the current has to flow though the other spark plug to complete the circuit.


01SE - check for spark again on the new coil. Check all the cylinders. Also double check your plug wire routing. If you're still having trouble with a new coil check these things: No spark on #1 only - check the plug wire for continuity. You might have an open or a short. No spark on #1 or #5 - check coil feed wire. There might be a wiring fault or the PCM driver is not functioning.

It's remotely possible that the new coil is also bad.



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post #30 of 58 (permalink) Old 05-11-2012, 09:25 PM
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Thank you, behlinla.

Wires are correct and a new coil gives spark on all of six outlets.

My idle fluctuates and car accelerates very ruff with shaking (with a gentle throttle input). Once up to speed, it's drivable.

Could IAC valve be a culprit to my problems? I did clean it twice in the past 2 years with Intake Medic spray and a toothbrush. I also run only Premium gas and synthetic oil. When I disconnect electrical connector from IAC valve, idle changes notably, so I'm not sure if my IAC valve is failing or a problem lies elsewhere?
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