Engine Surging

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Nov 19, 2008 | 09:35 PM

astone

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Engine Surging

Hi

A couple of weeks ago my truck started with a rough idle and surging, and then the check engine light came on. The CEL went out after a couple of days and the truck was running ok. The surging came back yesterday and seems to be getting worse, although no CEL. Today it was surging bad even when going 40-50 mph whereas before it was just at an idle and at lower speeds. I do not have a code reader and none of the parts supply stores around here will read codes. From what I have read it sounds like it could be a bad COP, IAC, vacuum leak, DPFE, EGR valve or plugged ports in the throttle body. I'm going to head out into the cold to take a look at the vacuum lines. I know it's difficult without codes but does anyone have any thoughts? Will a bad IAC only cause surges while idling, not driving?
Also the weather here is getting cold, would that make any difference?
Thanks
2003 Scab,4x4 4.6l, 108,000 km

Nov 20, 2008 | 08:52 AM

KingRanchMan02

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From: Louisville, Kentucky

You are on the right track by checking the vacuum lines. Take a good look at the hose between the PCV and the back of the intake manifold. The 90 degree portion of the tube at the very back of the engine is where it likes to rot out.

The IAC is only functional when the throttle is closed so, it won't effect the engine when you are driving except at stops.

You didn't say what year, model, engine and trans you have. You might want to consider getting a code reader if no one in your area does it for free. Good luck!

Nov 20, 2008 | 10:07 AM

astone

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Thanks John

I did not get out last night to check it out, it got too late. It is a 2003 4.6l 4x4 with about 108,000 km on it. I drove it into work today and barely noticed anything. I boggles my mind how it can change like that. It almost seems to get worse as it warms up. I will check the vacuum lines tonight. I take it I should check with the engine off first and if I don't see anything, start it up an see if I can hear anything?

Nov 20, 2008 | 10:40 AM

KingRanchMan02

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Yes, that is a good plan. LOL, I just noticed that you listed your truck information in the original thread and I totally overlooked it.

Nov 20, 2008 | 11:11 PM

astone

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Well, I finally broke down and bought a code reader. I have a P0304 Cylinder 4 Misfire Detected. From what I have read it sounds like I should be changing out that COP. Thats the one closest to the fire wall on the passenger side is it not? The plugs were just changed this summer. I will also check to see if the heater hose above is leaking onto the COP. If it looks like I'm going down the wrong path please let me know.

Thanks

Nov 21, 2008 | 09:14 AM

astone

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Any difference between purchasing a Ford COP or one from say NAPA?
Thanks

Nov 21, 2008 | 10:21 PM

astone

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I purchase a Ford Cop and put it on tonight. Took it for a 45 min. test drive under the conditions that seemed start the rough idle etc. So far so good, I hope it continues.

Thanks for your input KingRanchMan