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Old 07-03-2013, 07:23 PM   #1
FenixFallen
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New to SVTFs, have a stumble/stutter issue

Hey everyone, first post on these forums, but I have been reading around on this site for a little bit. I just picked up a 2003 Sonic Blue SVT Focus; I've been trying to figure out what's causing a low RPM stutter/stumble it has. It starts at 1800 and continues until maybe 2800 while I'm accelerating normally, most noticeable in second gear. The problem isn't as noticeable if I'm really stepping on the gas, only when I'm being civil with it, like driving through town. I've already tried replacing the spark plugs and wires, fuel filter, cleaned the MAF sensor and IAC. The stutter seems to have gotten smoother but is still there. I hooked up the scan tool to it and we aren't getting any codes. Could this be an ECU thing that could be fixed with a tuner? Are there any other things to try that I haven't thought of yet? I only run 93 gas. The car came mostly stock, HKS catback exhaust and eibach sportline lowering springs are the only real mods it has that I can tell. stock airbox. the previous owner gave me the receipts from when he replaced the timing belt and all the other belts, 6000 miles ago. Oh, and I can't seem to find the EGR valve or the DPFE sensor anywhere; looks like the DPFE used to be bolted to the firewall, but was removed to make room for a strut bar. Not sure how the car isn't throwing any codes if those were actually removed. Hopefully you guys can help, I'm running out of ideas. Thanks


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Old 07-03-2013, 07:28 PM   #2
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Possibly dumb question, but where do you get your fuel? I've realized a noticeable difference between "no name" fuel and Shell fuel, for example--to the point that I'm willing to pay the extra $.20 per gallon to get the more reliable performance.
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Old 07-03-2013, 08:13 PM   #3
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I almost always use Mobil or Sunoco, I never settle for no-name gas stations. I'm a little OCD about putting 93 in my cars, lol. my other car is a 2003 Mach 1 Mustang and the car I had before that was a '90 Honda CRX with a B16 swap, so I'm used to spending the extra on fuel for the high performance engines.

Speaking of fuel, how much MPG should I be getting? Maybe that's something I should be paying attention to, the last couple fill-ups were in the 22-24mpg range. the ride back from where I picked it up I got 27 mpg, but that was all highway. I was hoping for a bit better mileage than 24 but maybe that's all I'm gonna get in this state, we have a lot of hills.
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Old 07-04-2013, 03:19 PM   #4
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Quote:
Originally Posted by FenixFallen View Post
Hey everyone, first post on these forums, but I have been reading around on this site for a little bit. I just picked up a 2003 Sonic Blue SVT Focus; I've been trying to figure out what's causing a low RPM stutter/stumble it has. It starts at 1800 and continues until maybe 2800 while I'm accelerating normally, most noticeable in second gear. The problem isn't as noticeable if I'm really stepping on the gas, only when I'm being civil with it, like driving through town. I've already tried replacing the spark plugs and wires, fuel filter, cleaned the MAF sensor and IAC. The stutter seems to have gotten smoother but is still there. I hooked up the scan tool to it and we aren't getting any codes. Could this be an ECU thing that could be fixed with a tuner? Are there any other things to try that I haven't thought of yet? I only run 93 gas. The car came mostly stock, HKS catback exhaust and eibach sportline lowering springs are the only real mods it has that I can tell. stock airbox. the previous owner gave me the receipts from when he replaced the timing belt and all the other belts, 6000 miles ago. Oh, and I can't seem to find the EGR valve or the DPFE sensor anywhere; looks like the DPFE used to be bolted to the firewall, but was removed to make room for a strut bar. Not sure how the car isn't throwing any codes if those were actually removed. Hopefully you guys can help, I'm running out of ideas. Thanks
The SVTFs did not come with an EGR system which would include the DPFE sensor.

In regards to the stumble, maybe the 02 sensors (mainly the upstream).

There was also a firmware update issued by Ford for the PCM in the SVTF's that was supposed to address stumbling and poor performance issues. I would start by trying to identify what firmware version your computer is currently. If you have one of the firmware versions mentioned in that TSB (RLA1, RLA2, RLA6) I would consider going to a Ford dealer to get them to flash the YFR0 update onto your computer to see if it helps. Its possible one of the previous owners already had this done but its still worth looking into.

>This< is a good tutorial on finding your PCM version
>This< is the TSB about the YFR0 firmware update

It entirely possible that a chip could help clear this up. A lot of people have said a good tune cured their surging and stumbling issues. Along with a host of other improvements.
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Old 07-04-2013, 05:49 PM   #5
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that 1800-2800 rpm stumble is basically Ford's tune sucking. learn to live with it or get a retune and it will go away. all highway i get 30-32 mpg w/ the a/c on at 70-72mph. in the city I get about 20, but that's pretty much racing stoplight to stoplight.
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Old 07-04-2013, 06:11 PM   #6
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Just checked the PCM, it's got YRF0 on it, and if I'm reading the TSB correctly that means it already has fords update. I already replaced the spark plugs and wires. my dads a mechanic and judging by the plugs we pulled out there's no reason to believe the coil is bad according to him. we already replaced the fuel filter as well; the old one wasn't in very bad shape though.
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Old 07-04-2013, 08:25 PM   #7
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This is a very common problem with the SVT and a lot of them did this even new

I sell a tune that should cure your issues as well as make a better idle , better take off , better over all drivability

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Old 07-04-2013, 08:39 PM   #8
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Sounds like a plan, I was leaning in that direction anyway. I'm gonna do some shopping around for a good price on an xcal3; Or is there a better option for the SVT? I used an xcal3 from American Muscle with my Mach 1 so I'm familiar with it, haven't had any issues with that, but I do recall seeing a post where the SCT didn't want to work with an SVT, that's why I ask.
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Old 07-05-2013, 03:28 AM   #9
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Engine Stumble Problem

I had a stumble problem about 4 years ago that drove me nuts. Over a period of about a year it gradually deteriorated to the point where the engine would intermittently lose power and seemed to be running on less than all 4 cylinders. After reading other SVT owner forum posts about changing plug wires and coils I came across a comment about a wiring harness/connector issue. You'll want to check the three wire connector going into the coil. I believe there was a minor design flaw. The lead for that coil connector out of the harness is too short. This results in the lead bending sharply at the connector. The wire that bends the most eventually fatigues and separates at the connector causing the circuit to intermittently go open and prevent one or more cylinders from firing. There is a replacement connector available. I think the service part number is 3U2Z-14S411-TNA. When I cut out my old connector and spliced in the new connector with extra length wire I immediately got back to fun-to-drive mode. Good luck.
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Old 07-05-2013, 10:48 AM   #10
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I sell the xcal3 , full custom tune , free tune updates as you add more NA mods , datalogging services for 399.00 and 20.00 for shipping

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