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Discussion Starter · #1 ·
I hope that someone can shed some light on this situation I find myself in with my 2003 Taurus, 3.0 Vulcan engine. 133500miles.

About 3 months ago I put in new spark plugs, wires, and a coil pack and the car was running great.

1 Week ago I did something I rarely, if ever do. I floored it while getting on the highway, got up to 60 or so, leveled out and drove for a while. I stopped at a 7-11 and when I restarted had a blinking check engine light. I pulled the code out as P0302. A misfire on 2. I pulled the battery and reset the computer and the check engine is/was off but the car still was idling rough. I came to this board to see if I could find any advice for what to check. The light will remain out UNTIL I hit the highway again, then it will return, so something is triggering it there. But the idle remains rough, and you can feel a vibration when accelerating, even a little.


While parked and turned off I have pulled the IAC and it was fouled a bit, and at idle when I disconnect the IAC connector, the engine does die, so I think it is working OK. I did not clean it per Ford warning. I am checking for possible vacuum leaks but can't find or hear anything. The PVC elbow does have a few small cracks (I ordered a replacement.) I also cleaned the MAF (with MAF cleaner)


Now, I go back to the heavy foot I had last Saturday as I am not a jackrabbit driver normally and I think the excessive acceleration might have put some heaver than normal vacuum or stress on a part that was marginal. The question is, what part?


I am wondering if it might be as simple as a clogged fuel filter. (going to get it changed for good measure anyway)
Any thoughts would be appreciated.
 

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Are you ruling out spark plug because you put a new one in a few months back? It is an easy check though.
 

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Discussion Starter · #3 ·
Are you ruling out spark plug because you put a new one in a few months back? It is an easy check though.
Yes, only because the car was running great for 3 months since I replaced the plugs and wires. Over the last 48 hours, I"ve gotten two different misfire codes, a 301 and a 302. Only when I am on the highway. Local driving doesn't seem to trigger the codes (even though idle remains rougher than 'normal"

Thank you for your response.
 

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Engine vacuum is highest at idle and decel. At WOT the entire intake system is at virtually atmospheric pressure.
 

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Discussion Starter · #5 ·
Engine vacuum is highest at idle and decel. At WOT the entire intake system is at virtually atmospheric pressure.
Jeff, that is very interesting. I still can't explain why then it happens on the highway. Or perhaps after I am at speed, when I lay off the gas, the vacuum kicks up. I FEEL like it is a vacuum leak somewhere (again, a gut feeling only because of the way it all happened)-- I feel that a line may have cracked under some stress. Would the IAC have any effect at road speed or only at idle. I pulled the wiring off the IAC while at idle and the engine died. That is the only test that I know of. (other than popping for 60 bucks for a new one)-- I tried the tap test, with no change of idle.

Thanks for you input.
 

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Discussion Starter · #6 ·
Engine vacuum is highest at idle and decel. At WOT the entire intake system is at virtually atmospheric pressure.
after reading your input, I decided to try a test. I took the car onto the highway today (no codes but rough idle)--stepped on it hard to get up to 60mph, and stayed there for about 4 mins I then took my foot off the gas and just coasted. The car then gave me a blinking check engine light. The code was P0302 (misfire on 2)--

Not sure if any of that helps, but I hope someone can suggest a next test to try. Thanks.
 

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Vac leaks often show up the most at idle and decel when engine vac is at the maximum.
 

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Discussion Starter · #8 ·
well, I'm fixed

I want to thank everyone for their input. I was wrong in assuming it could not be a plug. We changed the plug in #2 and all is well with the world. Remember, I put in new plugs just 4 months ago. So problem was just that. Sometimes the obvious IS the answer.

Thanks again
 
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