misfire under hard acceleration - Taurus Car Club of America : Ford Taurus Forum
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post #1 of 17 (permalink) Old 06-18-2015, 08:38 PM Thread Starter
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misfire under hard acceleration

hi guys. I have a 2002 Taurus with the 3.0 duratec engine. When you start it, it idles and runs rough until you drive about 100 feet or so, then it smooths out. After that it runs well unless you give it more than 1/4 throttle from a dead stop. When trying to accelerate quickly from a stop or even from a roll it just stumbles and falls on its face and misfires like crazy. I have replaced the coil pack, wires and plugs within the last year. It also had a vacuum leak for a while that I just found and fixed which did not solve the problem. I got a code for cyl 1 and cyl 5 misfire but it has not thrown those codes in weeks. also it seems to idle rough when the air conditioning is on sometimes. other times the a/c has no effect. anyone got any ideas why it does this but does not throw a code? bad pcm? bad injector(s)? I'm at a loss
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post #2 of 17 (permalink) Old 06-18-2015, 10:05 PM
Has It Been That Long?
 
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What brand coil pack and plugs/wires did you use?

Rough idle with AC can be a vac leak issue, you may want to replace your upper and lower intake manifold gaskets. (Not too hard, there are tutorials here).

Holly: 2003 Taurus SES Deluxe, Duratec, spoiler, moonroof, OEM Centennials, JBL Audio. April '14 COTM winner.
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post #3 of 17 (permalink) Old 06-19-2015, 09:55 AM Thread Starter
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Quote:
Originally Posted by The White Falcon View Post
What brand coil pack and plugs/wires did you use?

Rough idle with AC can be a vac leak issue, you may want to replace your upper and lower intake manifold gaskets. (Not too hard, there are tutorials here).
Thanks for the reply. I'm pretty sure it is not a vac leak or the intake manifold gaskets because I had it smoke tested to find original vacuum leak. and we replaced the faulty vacuum hoses. There was a little oil in the #5 spark plug hole when i inspected the plug the other day. I cleaned it all up and the oil has not come back. I wonder if the valve cover gasket could be the cause of a vacuum leak

edit: the wires I used were the more expensive ones at the auto parts store, i forget the brand, and the coil pack was probably a cheap autoparts store brand. The plugs are motorcraft stock replacements
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post #4 of 17 (permalink) Old 06-19-2015, 10:01 AM
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Well, the only coil packs worth anything are the BWD and Motorcraft units, so you could have a defective coil still.

As for the intake manifold gaskets, the leak can be quite small and only show up under a heavier load. Over 100k those need to be replaced without question.

Holly: 2003 Taurus SES Deluxe, Duratec, spoiler, moonroof, OEM Centennials, JBL Audio. April '14 COTM winner.
Jill: 2010 Taurus SEL, 3.5L Duratec, Sync.


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post #5 of 17 (permalink) Old 06-19-2015, 10:06 AM
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There have been failures reported on aftermarket coil packs other than BWD. I am confused, were the codes cleared from the last occurrence and have they reappeared? Given the history have you checked signal pulse on the coil connector? You may have an issue at the connector or a chaffed wire

It's SHO time!


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post #6 of 17 (permalink) Old 06-19-2015, 10:08 AM
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How's the pcv hose/tube assy.?
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post #7 of 17 (permalink) Old 06-19-2015, 10:51 AM Thread Starter
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the lean codes went away when we fixed the vacuum leaks. The misfire codes have not come back since clearing them weeks ago. it is strange because it idles like crap when you first start it then after you drive for 30 seconds it clears up and only stumbles under hard acceleration. I'm going to check the wires tonight. I wish the coil wasn't under the intake, such a pain to get to
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post #8 of 17 (permalink) Old 06-19-2015, 10:57 AM
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How long ago was the smoke test done? In the absence of codes it sounds like Sheila's suggestion of a PCV hose or some other source of vacuum leak

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post #9 of 17 (permalink) Old 06-19-2015, 10:59 AM
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Have you checked the compression or perform a cylinder leak down test. Perhaps it's a valve leaking. That's if all else checks out with the ignition system.


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post #10 of 17 (permalink) Old 06-20-2015, 03:46 PM
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When I replaced my engine (01 Vulcan) I had a really bad miss and it was showing a lean code for bank 1. I had the injectors from my old, blown engine, also an 01 Vulcan. Known good, so I rehabbed them by cleaning the injectors with undiluted, pressurized injector cleaner & a 9v battery to fire them, and new o-rings. Solved the miss and killed the code immediately. I'm thinking you might have one or more bad injector.

In the past, I have had a miss from one seeming new, but defective plug wire. New wires solved it. (On a Lumina.)

You may be able to check your ignition with an inductive timing light. We old school guys have them in our "useless" tool boxes--where infrequently or never used tools go to collect dust. Got a ring compressor and a valve spring compressor and a never used drum brake spring expander in mine. As soon as I'm done with my front suspension my pitman arm/ball joint and tie rod compressors will join them.
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