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SVT with sudden rough idle, power loss

19K views 81 replies 18 participants last post by  qweesy 
#1 · (Edited)
My SVT very suddenly started to run like crap. Here's the situation. Filled up with gas today. Car has been running quite well, got 29 mpg on the tank on a 250 mile trip. On the way home, a few miles from the gas station the car starts to lose power and runs really rough in gear or neutral. Sounds like rocks rolling around when I apply throttle, gargley and deep sounding. I coast to a stop in neutral, with the car stumbling the whole time. Shut it off. Turn back on and it can barely idle, requires throttle to keep from stalling. Runs terrible, sounds dangerous even. Shut it off. Called AAA and had it towed to my local shop. It's sitting at the repair shop for them to diagnose tomorrow. No CEL through any of this.

Hopefully its something simple, I'm suspecting fuel filter or pump... Better not be timing related since that was done 55k miles ago.

More info:
Car has 135k miles.
Fuel filter mileage unknown, could be quite old as the filter, bracket, and nuts are very rusted. (Which is why I haven't gotten to it.) No mention of it being changed by PO, who kept decent notes and was a Ford mechanic.
For past few months car has had a slight stumble at cruising speeds and occasionally threw P0133 and P0172. Changed O2 sensor, reset ECU, car has run much better since with no codes, but still not 100.0%.
Has Toms Tune. No issues with the tune AFAIK.
New Motorcraft copper plugs and CFM wires.
New Alternator.

Basically, I'll see what the shop has to say tomorrow, but I'll back up their thoughts with what the FF community has to say. [ffrocks]


UPDATE WITH RESOLUTION:

It was bad gas. Really.

Shop replaced the fuel pump and filter. Still ran like garbage, very difficult to start it. Sat for a few weeks in the cold. Tom (1turbofocus) helped me get it started and debugged. I got the car running with the gas on intake trick. Once it was warm it ran ok, but felt down on power, like 50%. Figuring it might just be as simple as bad gas, I put some Heet and Seafoam in the tank and tried to drive it off. Put 100 miles on and it ran better as it went, almost completely back to normal. Still had a small hiccup between 1500 and 2500 rpms, usually in second gear. Filled it up with gas again and let it sit overnight in the cold. It fired right up the next morning. Ran better and better over the next few days, and no issues since. Boo Citgo!
 
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#6 ·
^^ My thinking as well.

Another thing to add: Car sat overnight on the shop's lot. I tried to start it this morning but it wouldn't. Seemed like it wasn't getting fuel.



I was hoping for this (free fix!) but intake piping was nice and tight. Couldn't find any other red flags under the hood either.
 
#5 ·
Well, I guess that's one good thing about not changing the fuel filter- you'll change it when you change the pump. My pump has 150k miles/8 yrs on it, and the filter has been changed every 25-30k like it should be. I'm curious as to when it will go out.

As a guess, yes, it is fuel pump/filter time. The engine running conditions you described are similar to fuel starvation. You might expect a CEL, but it probably didn't run with the condition long enough to pop up a CEL.
 
#7 ·
In the future, listen for the fuel pump to buzz. On a Ford, if it doesn't buzz, that doesn't mean that the fuel pump is out- there is still the fuel cutoff, and the fuel pump module. About 90% of the time when it doesn't buzz when you turn the key to ON, that is the fuel pump.

Change that fuel filter every 25-30k miles, and if rust and abuse is a problem up there in WI, then use nickel anti-seize under the bracket, and on the threads of the bolt that holds the bracket down. It's messy, but it works. I buy this stuff by the bottle. It's a lot cheaper than purchasing those $1 tubes. It separates due to temp changes and non-use, but just stir it with a screwdriver- no harm done.
 
#8 ·
Can't recall if I heard the pump this morning, usually I listen for it to run before turning the key from Run to Start.

"if rust is a problem up there in WI"... You southerners, so funny. [hihi]
 
#12 ·
Start your own thread. The problem that the OP is having in this thread is not even related to a timing belt.

Look at the threat title above where these posts are. You'll see something like Focus Fanatics> Ford Focus Tech Discussions> General Technical Chat> SVT with sudden rough idle, power loss.

Click on "General Technical Chat", and a new list of threads will appear. At the top left side of that list, you will see a yellow button that reads "Post New Thread", click on that, and describe your problem, your vehicle, and your mileage. That is the best way to get answers on this forum. Thanks for posting!
 
#11 ·
Nope, local shop in my small town.
Ford says 100k or 120k I think, but most folks on this forum say to do it every 80k or less. Probably a good idea for you to start thinking about getting it done!
 
#13 ·
Fuel filter and pump replaced. Fuel pressure was abysmal before, it's optimal now. Filter was likely original (135k miles!) and pump was full of crud. Car will start now, and may run well for 5-10 seconds, then falls on its face and stalls. Seems to do better with throttle applied. (This is what shop told me, haven't driven it myself.)

They're stumped, and I told them not to throw parts at it, I'll just take it home and try to figure it out myself. I think it's drivable at this point.

Still to check:
  • Vacuum leaks, I checked the easy ones, haven't gotten to all of them yet. Shop wanted $80 to do a smoke test. Eff that.
  • Coil pack pigtail wiring.
  • MAF sensor. Don't want to replace it if I don't have to, they're surprisingly expensive.
  • Dump some Heet in the tank, possibly due to water in gas.
  • Try to return to stock tune, reset ECU by removing negative cable. Perhaps ECU is confused with a properly operating fuel system?
  • Send a datalog out to Tom, maybe he can see something I can't.
Any other suggestions..?
 
#14 ·
Maybe a failing o2?

Before changing the primary o2 sensor (for the second time), my car would run fine for a bit, and then randomly run like garbage. It too was better with some throttle applied than with it being at idle or even just above.

Should throw a CEL, but mine didn't always...
 
#15 ·
Front O2 sensor replaced less than 1k miles ago. It was throwing codes for that. No more codes, and running condition improved after the change.
 
#16 ·
...of course it did. Bleh. I'm running out of ideas.

On a scale of one to shit, how does it drive?

It seems like you may have just a bunch of minor-ish problems that finally added up to something substantial?

How're the plugs? Wires (do they arc when wet)? I'm leaning toward electrical.
 
#17 ·
I haven't driven it since the fuel pump was replaced, but it was about 9/10s of shit when it first happened. I'll be picking it up tonight after work.

That's what I'm thinking too, a bunch of little stuff making it run a bit goofy, then the fuel filter/pump was the straw that broke the camel's back. Plugs and wires are new-ish, less than 7k miles on them.
 
#19 ·
So. Go to pick the car up at shop after work, service manager tells me its not really driveble and will drop it off at my house free of charge in the morning. I went to poke around under the hood one last time, but now it won't start again... Turns over just fine, just never fires off. Starting to get worried now.
 
#20 ·
It sounds like you're getting fuel. Did they check for spark?

I recently bought a focus with a malfunctioning crank sensor and a dead O2 sensor. Drove like crap!

Maybe your crank sensor has died? Maybe a bunch of bits of nasty that wrecked your fuel pump is now in the injectors?
 
#21 · (Edited)
Should be getting spark, my guess is fuel isn't getting into cylinders. Fuel pressure is good at the rail, but is it possible the computer isn't telling the injectors to fire properly?

I'll add crank sensor to the To-Check list.

Other things (I'm adding things as they come to my mind, otherwise I'll forget them!)
  • Check crank sensor and wiring. On trans bell housing, near exhaust header? "The crankshaft position sensor connector melted."
  • Coil wiring and stuff. Links here and here
  • Reset ECU by disconnecting negative battery cable. Apparently shop forgot to do this.
  • Check if fuel cut-off switch was set or is malfunctioning. The one in the passenger footwell. "You can bypass the inertia switch if you think it might be the problem. All you have to do is bridge across the connector with a piece of solid insulated wire, or a paperclip as long as you make sure there's nothing it can short on. I would not make this permanent, but it can serve the purpose of identifying if that is the problem. "
  • Fuel pump relay - R7. Fuel pump fuse - 12.
  • Fuel pump driver module. "passenger side, flip the back seat forward and pull the carpet up and you'll see the fuel pump driver module"
    __________________
 
#22 ·
Crank it and pull the plugs. Are they wet/smell like fuel? I don't think you have a fuel problem. I'm still thinking it's electrical -- especially if the shop had it running at one point.

Check for reliable spark at the plugs...maybe a bad coil.

IIRC, the coil on our cars is sort of split into two (one part, but I think it's divided internally). I remember getting strong spark on two cylinders, and basically nothing on the other two at one point.
 
#23 ·
Crank it and pull the plugs. Are they wet/smell like fuel? I don't think you have a fuel problem. I'm still thinking it's electrical -- especially if the shop had it running at one point.

Check for reliable spark at the plugs...maybe a bad coil.

IIRC, the coil on our cars is sort of split into two (one part, but I think it's divided internally). I remember getting strong spark on two cylinders, and basically nothing on the other two at one point.
I'll get the car back in the morning. Gonna take a half day of work, maybe whole day, to try to figure this out. I'm thinking it might be the crankshaft position sensor, or its connector/wiring. Or coil pack and its connector/wiring.

How exactly do I check for good spark at the plugs (the safe way)? I believe they are getting spark, since the shop did have it running, but not sure if the spark is reliable, like you said.
 
#24 ·
I had a similar issue, and it turned out to be a bad ground, and bad fuel module... The bad ground i noticed because everytime i hit a bump the car would shut off... tightned it and then the car started to run like crap.. replaced the fuel module and that fixed my issues.. it also solve a sputtering issue i had over 5k rpm.. im having a slight sputtering issue again but i think its the plugs.. i will be changing those soon.
 
#26 ·
Saga continues. Car is home in garage now, still won't start. Cranks fine, and occasionally sounds like it's getting both spark and fuel, but won't run. All wiring looks ok, but that can be deceiving. Still no CEL. I have tried resetting ECU, pushing the inertia fuel cutoff switch button, and repluging various sensors. Got a catalog as well, and from what i can tell, fuel pressure, MAF counts, and throttle position look good. I sent it off to Tom for confirmation.

But alas, all of this is the least of my worries now. I tried to load the stock tune back on, but the SCT tuner fails the download and car is dead. I've had lots of problems with my tuner before, but thought I had it cleared up.

If I can't get the stock tune back on, and if SCT cannot help, I may have to replace the ECU...
 
#28 ·
Car is tuned right now. I cannot load custom tunes to it because the tuner complains about "..custom tune failed, return to stock, yadayada." When trying to install stock tune, it gets to around 11%-17% complete, then beeps and says tune failed to load. Error 1016 I believe.

I have fuses 46 and 61 pulled. Gonna buy a battery charger after work to make sure battery didn't just get stressed out from all the failed starts. I've heard the SCT tuners are picky about battery voltage.
 
#29 ·
Well, at least it still tries to load the stock tune -- that's a good sign, as long as the stock tune is still intact on the tuner.

The battery idea makes sense, especially if it's been cranking the engine in the cold for a few days now...

Might be time to give SCT a call otherwise.
 
#30 ·
Car is back to stock tune. Yay. What worked was pulling fuses 20, 46, and 61, turning the key to RUN as soon as it prompts it, and lots of swearing and threatening language towards the tuner lol. It's not a tune problem anyway, so returning it to stock just made me give myself more of a headache than I needed lol.

Tom (1turbofocus) suggested doing a compression test before moving further. I think I'll so that. I won't be able to work on the car until Sunday though, which sucks. If the compression is low, I'll be one sad dude...
 
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