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Discussion Starter · #1 ·
This is a follow up post to this earlier one that I had posted.

http://www.focusfanatics.com/forum/showthread.php?t=265876

Zetec engine
I have changed to new Motorcraft wires, which helped a lot , but didn't " cure " everything, so I put in a new fuel filter. Helped , but still not running great yet, & still lower,,, but better mpg. I have inspected coil wire harness & it looks good but the wiring is pretty short going to the coil. It idles great, no codes stored , BUT mostly when accelerating, is when I notice a problem. If I turn a/c it is even worse when accelerating & there is some light " skipping / bucking " , etc. , at higher rpms. Good fuel system cleaner has been added to several tankfulls, almost new Motorcraft plugs, problematic PCV hose is fine, etc. The car only has 53,000 miles, but is a 2003. I am leaning toward replacing the coil & wonder what the experts here, think. ???? Thanks
 

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First of all you need three things. Compression, fuel and spark. Do a compression check on everything even though you think its fine which it probably is I would do it to eliminate it. Next if its idling does it rev up easily? Does it buckle then? Does it do under a load? For fuel injectors ohm out the injectors and make sure their resistance is all the same across the board. If they are not then you know you might have a slightly stuck injector. Also clean the maf, check the air filter. What are the plugs gapped at or are they new? Coils go bad on fords a lot of times but do this first.
 

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Discussion Starter · #3 ·
It idles just fine. MAF has been cleaned & air filter replaced. The problem is under load, accelerating, especially with a/c on. Plugs have less than 7000 miles & are gapped correctly. Will check into the other items.
 

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It idles just fine. MAF has been cleaned & air filter replaced. The problem is under load, accelerating, especially with a/c on. Plugs have less than 7000 miles & are gapped correctly. Will check into the other items.
Ya let me know what you come up with.
 

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Discussion Starter · #7 ·
Update ;

I haven't reported back because the problem " fixed " itself for 2 tankfuls of gas. NOW,, the problem is back again. Slightly noticeable without a/c on, but turn it on & it is a problem. MPG has picked up a bit , 30mpg combined , but not up to the 32-33 that I was getting. I live in a rural area & was getting 32-33 you a couple of years . I am going to put a coil on it & see if that corrects it. I have a code scanner & still nothing shows up. I don't have a scanner to check fuel pump pressure.
 

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Read in the manual for your scanner to see if it does data logging. That's how you get the information you need.

To me, it sounds like you might need to clean your IAC and reset the PCM. The IAC could be stuck open, and the PCM is compensating for it's position which would give you issues like a PCV vacuum leak at high rpm.
 

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Discussion Starter · #9 ·
Read in the manual for your scanner to see if it does data logging. That's how you get the information you need.

To me, it sounds like you might need to clean your IAC and reset the PCM. The IAC could be stuck open, and the PCM is compensating for it's position which would give you issues like a PCV vacuum leak at high rpm.


The car idles fine. Do you think the valve still needs cleaning to correct its problems ?
 

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Your problem sounds very similar to mine. I have a mild surge while driving at a constant speed which is more pronounced when the a/c is on. My fuel mileage is also less than expected. I've done the following; new plugs, plug wires, EGR pressure sensor, replaced pcv hose, cleaned pcv, new air filter, cleaned the MAF and IAC and reset the PCM. This seems to be a problem for many of the Zetecs. Strangely though my old ZX-2 Zetec didn't have this problem. Mileage was always in the upper 20s to mid 30s. It did have VCT which changes or eliminates the EGR system if I remember correctly. This leads me to believe it may be EGR related. I tried the EGR focus hack and all I got was a MIL. I also read somewhere that it may be the fuel rail pressure sensor.
 

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My car used to do this...4k+ it would start to misifre and i couldnt go WOT because it would spit and sputter horribly. Last 2 fill ups i got 16mpgs :(

So i just tightened the hose clamp to my air filter,which was a horrible fit and kept falling off and viola, back up to 30mpgs. WOT Shifiting NP :)

In your case though, honestly i think yur going to need a scanner to datalog PIDS. An alertnative to using a scanner would be going to each individual components(EGR related, IAC, etc..) and measuring voltage BUT this is only helpful at idle, or part throttle no load.

But theres MAANNNNY things that can cause a misfire, i dont think you should just throw parts at your car but ill give you a list from the top top of my head.

Open EGR anytime other than cruise, bad plugs, bad wires, bad coil, low compression, IAC, Intake leak (MAF based), Exhaust leak, bad 02, faulty inj...and soi on and so on. Scan tools help narrow results
 

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It has been scanned many times & there has never been a code detected in the car.
I never said look for a code. I said use a scan tool to datalog, meaning monitor PID values, under real time. This is kind of hard to do when you dont have access to one, and im sure most shops would charge you diag time, unless you have friends who works at a shop and wouldnt mind helping you out. Other than that it may be somewhat difficult to diag without one. You also would need the specs to compare the values to, which again, shops have access to if they have programs like shopkey or alldata or whatever the Ford dealership uses.

You can just throw parts at it but thats never recommended
 

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Discussion Starter · #15 ·
I never said look for a code. I said use a scan tool to datalog, meaning monitor PID values, under real time. This is kind of hard to do when you dont have access to one, and im sure most shops would charge you diag time, unless you have friends who works at a shop and wouldnt mind helping you out. Other than that it may be somewhat difficult to diag without one. You also would need the specs to compare the values to, which again, shops have access to if they have programs like shopkey or alldata or whatever the Ford dealership uses.

You can just throw parts at it but thats never recommended
Well, I misunderstood you. I don't have access to one . It was at the dealer for this problem, once , too. They monitored it with me driving & said that they noticed what I was talking about, but it was acceptable.
I don't usually " throw " parts at a repair & that is one reason why I am asking members here.
 

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Discussion Starter · #16 ·
I'm regularly getting 23mpg average in my 05 manual now. I drive fairly conservatively and no codes.
That is very low, at least for my driving. My conditions, rural flat Florida ARE more ideal to get better mpg. I am trying to get mine back up to about where it was. Before ethanol,, I would routinely get about 35 mpg, but that is mostly 50-65mph rural driving. Ethanol instantly knocked it back to 32-33 .
 

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That is very low, at least for my driving. My conditions, rural flat Florida ARE more ideal to get better mpg. I am trying to get mine back up to about where it was. Before ethanol,, I would routinely get about 35 mpg, but that is mostly 50-65mph rural driving. Ethanol instantly knocked it back to 32-33 .
When I had an 03, which I got rid of due to lack of A/C, I was getting 33mpg hwy. With the 05, I've broken 30 once or twice. It's been going down since though. I average 23-25mpg now. I don't think its ethanol. I'm in Oregon and we've been 10% ethanol state wide for a very long time. It used to be searsonal, but since 09 or so, its been year around.

Right now, I may get 29 to 30 not using A/C, light traffic and cruise control on freeway at speed limit. Mixed driving gets me around 23 by reset odometer at fill and divide odometer by next fill up gallon method.
 

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Discussion Starter · #18 ·
Well, it WAS the coil ! I installed a new one, reset computer , & it has been running MUCH better. I haven't driven it enough to check MPG, yet, but I can tell it will be better .
NOTE;
I looked deep inside the spark plug terminals of the old coil, & on #4, there was a gunky , gooey , green build-up at the bottom of the hole. I imagine this was causing a slight short to the fire on that spark plug.
 
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