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Old 06-05-2007, 08:37   #1 (permalink)
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confused Rough idle P0301, P0316, with A/C on only

I have a 2002 Ford Taurus SEL with the 3.0L DOHC engine. It has had a rough idle for a few months now.
I have read codes P0316, P0301.
I replaced the spark plugs, the old ones were worn but the new ones didn’t improve the idle problem.
Swapped cylinder 1 and 2 injectors still got P0301.
Next I replaced the coil pack and that fixed the problem for about 3-4 weeks, then the rough idle problem slowly returned, now it’s as bad as it was originally.
The only code since the coil replacement was P0300.
I have noticed that the rough idle stops immediately when the A/C is turned off.
Not sure what to check next, since replacing the coil fixed the problem for a short time that makes me think it’s not a mechanical problem (compression, fuel pressure…).
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Old 06-05-2007, 16:15   #2 (permalink)
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Question Re: Rough idle P0301, P0316, with A/C on only

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Originally Posted by slarson03
I have a 2002 Ford Taurus SEL with the 3.0L DOHC engine. It has had a rough idle for a few months now.
I have read codes P0316, P0301.
I replaced the spark plugs, the old ones were worn but the new ones didn’t improve the idle problem.
Swapped cylinder 1 and 2 injectors still got P0301.
Next I replaced the coil pack and that fixed the problem for about 3-4 weeks, then the rough idle problem slowly returned, now it’s as bad as it was originally.
The only code since the coil replacement was P0300.
I have noticed that the rough idle stops immediately when the A/C is turned off.
Not sure what to check next, since replacing the coil fixed the problem for a short time that makes me think it’s not a mechanical problem (compression, fuel pressure…).
When you did the Coil Pack or the plugs did you replace the plug wires??? I did plugs on my 2001 Taurus SEL 3.0L Duratec without the wires and got a misfire at idle. After replacing the wires, the misfire was gone. Look at the porcelin insulators where the plug wires attach. If you see black thin burn lines then the plugs were carbon tracked, meaning the plug wires are too, causing a flashover, and hence, a misfire.
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Old 06-24-2007, 09:57   #3 (permalink)
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Re: Rough idle P0301, P0316, with A/C on only

I have a similar problem with Merc. Sable 2002, 24V. Engene running rough with A/C on, only. Cylinder Ballans test shows that, sometimes, cyl.1 have misfire.
I replaced the spark plugs, and sp.plug wires (In cyl.1 - twice). Sp. plugs, and sp.plug wires was fine, and this does not help.
Now, I have two choices. The first is to replace the coil pack. Second - reprogramm computer (PCM).
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Old 06-24-2007, 11:31   #4 (permalink)
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Re: Rough idle P0301, P0316, with A/C on only

Needs the air adders modified. See if the dealer has a reflash upgrade for you or make sure the IAC is working as it should.

Cheap and permanent fix is to open the throttle plate just a hair, disconnect the battery then let the car relearn idle.

To set the throttle stop screw..........

Only make the following adjustment in the event the TRC screw does not contact the throttle lever arm.


1.) PLACE a 0.002 inch feeler gauge between the TRC screw and lever arm. ADJUST TRC screw until it just contacts the feeler gauge.

2.) REMOVE the feeler gauge and turn the screw clockwise a half turn.

This should leave the throttle plate just a hair open which reduces binding and also gives the IAC more headroom.
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Old 06-24-2007, 11:35   #5 (permalink)
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Re: Rough idle P0301, P0316, with A/C on only

The procedure for relearning the idle is ....

On a warm engine, disconnect the battery for a minute. Start the car and let the idle stabilize in park at around 650-750 rpm. The shift to reverse and let the idle stabilize. Then turn on the AC MAX, making sure the temp setting is low enough to kick in the compressor, when still in reverse and let the idle stabilize. Then shift to park with the AC still on and let the idle stabilize.
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Old 06-24-2007, 12:11   #6 (permalink)
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Question Re: Rough idle P0301, P0316, with A/C on only

Quote:
Originally Posted by SHOZ123
Needs the air adders modified. See if the dealer has a reflash upgrade for you or make sure the IAC is working as it should.

Cheap and permanent fix is to open the throttle plate just a hair, disconnect the battery then let the car relearn idle.

To set the throttle stop screw..........

Only make the following adjustment in the event the TRC screw does not contact the throttle lever arm.


1.) PLACE a 0.002 inch feeler gauge between the TRC screw and lever arm. ADJUST TRC screw until it just contacts the feeler gauge.

2.) REMOVE the feeler gauge and turn the screw clockwise a half turn.

This should leave the throttle plate just a hair open which reduces binding and also gives the IAC more headroom.
OK, so how do you know the engine doesn't have a carboned up or burned valves??? I'd make sure the cylinder in question doesn't have excessive leakage during a leakdown test before toying with the throttle body adjustment. If you had a stalling issue and a low idle speed then maybe I'd consider re-adjusting it.
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Old 06-24-2007, 14:24   #7 (permalink)
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Re: Rough idle P0301, P0316, with A/C on only

Well other than the fact cars today seldom burn up valves I don't know. Just offering suggestions that have worked for me.

I don't see how opening the TP and taking some load off the IAC would hurt anything though.
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Old 06-24-2007, 14:46   #8 (permalink)
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Re: Rough idle P0301, P0316, with A/C on only

I have a more complex situation. Engine makes about 1 misfaer (cyl 1, only) every minute if the AC is switched on, transmission shift to reverse or drive, and car is not moving. In any other situation, engine running like new. Cylinder Ballans test-100% in all cylinders. Injectors -pass. Missfire - pass. Long fuel trn. 0%. Short fuel trn. +- 2%.
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Old 06-24-2007, 17:05   #9 (permalink)
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cool Re: Rough idle P0301, P0316, with A/C on only

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Originally Posted by SHOZ123
Well other than the fact cars today seldom burn up valves I don't know. Just offering suggestions that have worked for me.

I don't see how opening the TP and taking some load off the IAC would hurt anything though.
It doesn't happen allot but I'd say it's a little more than seldom. Just a little carbon build up from short trips and no heavy acceleration or highway driving causes leakage around the valve and eventually burning. I see it every so often on DCX cars. As for costless, is it setting a Check Engine light???
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Old 06-24-2007, 20:24   #10 (permalink)
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Re: Rough idle P0301, P0316, with A/C on only

Thank's SHOZ123 for simple method for setup throttle stop screw. I can change the position of throttle with additional nuts. This will save the original setting. In a situation where we have a DTC P0316 (misfire on startup) and / or P0300 (random misfire), setting the throttle stop screw may help.
The same, only in Russian:) Большое спасибо SHOZ123 за простое объяснение как настроить регулировочный винт дроссельной заслонки. Для эксперимента, я накручу на регулировочный винт дополнительную гайку и с ее помощью изменю положение заслонки. Таким образом мне удастся сохранить начальную настройку регулировочного винта. В ситуации, когда мы имеем коды: P0300 (пропуски зажигания в случайном порядке) и/или P0316 (пропуски зажигания при старте двигателя) - этот метод может помочь. Конечно, при условии, что нет утечек вакуума.
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