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Discussion Starter · #1 ·
Searched but could not find an identical problem.

Recently I bought a 2007 Focus ZX3. It is a 5 speed, and my first manual, so the first little while was spent learning how to properly shift it.

I've got my basic shifting technique down, but a problem emerged.

Sometimes the car would buck violently. So violent, I'd be thrown out of my seat had my seatbelt not been on. The tires would screech and it would feel like the whole front end would hop. This problem came and went.

It happened mostly when:
-First driving the car, when the engine is cold (after revs have dropped). Colder days seem to make it worse.
-First starting up the car, and passing the first couple of stop signs. Even if the engine is warm. Less shaking than the previous scenario.

It would only happen when I'm coasting, or when I first let off the gas.

It would be like this:

Clutch, first, start off smoothly. Off the clutch. Approaching stop sign, foot off the gas *SHAKES VIOLENTLY* back and forth a couple times. It usually happens when I'm not touching any pedals. Mostly in 1st and 2nd gear. Brakes reduce the shaking by about 80%, but the revs still bounce around.

Car was still under warranty so I went to the dealer. They diagnosed it as bad engine mounts. Took them 5 days to order the parts and replace it. They replaced the engine mounts, transmission mounts, and "torque restrictor."

When I drove it off the lot, it felt like a completely new car. The car feels much smoother and much quieter to drive, but the symptoms are still there. Maybe the tires don't chirp and I don't get thrown out of my seat, but it still shakes under the same circumstances.

I could bring it back, as the powertrain warranty isn't expired yet. But I'd prefer it if I didn't lose my car again for 5 days.

I was just curious if this problem was an easy/cheap fix, and if I could do it myself. I have very limited technical knowledge, and I've never worked on a car before. I'm thinking it might be fuel-pump related?

39,000 km on the odometer. No check engine light.

Any thoughts? I'll probably go back to the dealer if no fix is found/it's a difficult job. Appreciate any help.

Edit: Forgot to mention, 1/5 times the car doesn't start on the first crank. Clutch is to the floor.
 

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Does your car have a tach? when it starts to shake what are the RPMs?

Mine has this issue if it idles anything under 1000 for some reason. It doesnt always do it though ive played around with my idle and the lower it is the more it shakes.
 

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Discussion Starter · #3 ·
Usually around 2k-2.5k it shakes, as soon as I'm off the gas. Clutching or adding gas cures it.

I guess I should describe the shake in more detail.

It's not a consistent "rumble." It's a violent bucking, oscillating every second, back and forth. It always clears after driving for about 2 minutes.

The revs would be like this:

(accelerating) 1600....1800....2000...(off gas)....1800....2000....2000...2000...1800....2000...2000... etc
 

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No check engine light? With that high rpm it's probably not a motor mount, those are generally more violent at lower rpm or when engaging a gear. That sounds like a vacuum leak to me- my guess being the PCV valve line which is not so easy to change. You can find it under the intake manifold from under the vehicle- and there's not much room to work in there. It will be the rubber hose that goes from the intake manifold to a black box on the side of the engine block above the oil filter outlet. Grab the hose and wiggle it to see if it's cracked. If it is damaged or pulled off, then cap off the intake manifold vacuum port until you can get the hose to change it. I'm going to try to do this by partially removing the intake manifold sometime soon with intake manifold gasket replacement.

Now before I did that, I'd check something else much easier that might be related- although I'd be surprised that you didn't get a check engine light. Your problem seems to me to be a typical engine running problem at a certain rpm. I doubt it's the DPFE that is a common problem on other vehicles because yours is built into the EGR instead of being 2 parts that work together. I'd go through what passes for a typical tune-up on these engines. You'll need a few things: owner's manual, anti-seize, spark plugs, new fuel filter, and spray MAF cleaner. Now first read in the owner's manual about how to test your air cleaner in the maintenance portion. Test the air cleaner, then remove the MAF and spray MAF cleaner in both sides, shake and re-install. Be sure to look closely at the holes in the side of the MAF before shoving a straw in there. There are resistors that you could knock off if you're too abusive with it. You'll need a torx T15 screwdriver to remove it. On to the fuel filter: read on this site about how to change the fuel filter. I can tell you from experience that removing the fuse to the fuel pump doesn't always work to remove fuel pressure. Unplugging the fuel-cutoff switch is a much better method of relieving fuel pressure. Also, you do not remove the white clips from the fuel line to disconnect the fuel line. Practice on your fuel line on the engine after removing pressure from the line: press on the rectangular white spot until you feel it click (might have to wiggle it back and forth a bit to click) then pull the line off. That will help you when you're on your back under the car doing the fuel filter. FYI: WIX fuel filters come with the old and new fuel line clips in case you break one- but if you remove the line correctly then you shouldn't break it. Finally, move on to the spark plugs, which is where I think your problem might be. Remove the spark plugs- yes those should last longer than the miles you have on the car, but you'd be surprised what damage is done to plugs in vehicles that aren't driven often. If you don't want to put up the money to replace the plugs just yet, then you can probably clean these with a small wire brush without a problem. The factory Ford plugs have a very fine tip, so I wouldn't recommend using a knife to clean the hook. Brush the plugs clean, then check the spark plug gap- it should be .050 to .055. While you have the coils out, twist the boots to break the rubber boot loose from the coil, and pull it off. There's a spring in there that connects the terminal on the coil to the plug inside the boot. If there is green corrosion on the coil terminal, clean it off and put a thin coat of anti-seize or grease on the terminal before putting the spring and boot back on. That will help prevent future corrosion. Ford puts coatings on there, but it wears off.

I believe you'll find your problem in the spark plugs (likely incorrect gap), but the rest of those repairs are well needed. Fuel filters should be replaced every 35km or yearly. The air filter should be checked monthly, or any time you have problems. Those are supposed to be lifetime filters, but that doesn't prevent it from being physically damaged. Most people replace Ford's filter with an aftermarket filter- you can ask about that in the Duratec Performance chat forum. Ford wants about $300USD for a replacement lifetime filter- and those didn't work that well.
 

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Discussion Starter · #5 ·
The mileage was only 33,000 when I bought it, and it's only been a couple months since, so I'm suspecting it has been sitting for a while.

I bought some new spark plugs, some anti-seize grease, and a tune-up kit. Hopefully it's all I need to attempt my first spark plug change. The plugs were only 14 bucks so I might as well replace them, instead of cleaning the originals.

I'll let you know how it goes.
 

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Well, that fuel pump is needed, so check that out sometime. The procedure is detailed on this site in the how-to archives. Don't fret about year differences, all Foci up to 2012 have the fuel filter in the same location. It should be changed every year or 25k miles or 40k km, whichever comes first.
 

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Discussion Starter · #7 · (Edited)
Wait... fuel filter or fuel pump? I think my fuel filter was replaced during my last oil change.

I changed the spark plugs. Although the engine feels a little more punchy, it didn't solve the problem.

What would be the next easiest thing to tackle?

Edit: I might be mistaking the oil filter with the fuel filter. Pardon my inexperience.
 

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Discussion Starter · #8 ·
An update.

I replaced the TPS, and while there, cleaned out the throttle body. I think the previous owner overdid it on the rustproof, and some of the material made it's way inside the throttle body.

This made the throttle feel more responsive, and I don't get the rev-hang like I did before. The throttle valve must have been getting stuck open. It's not what I meant to fix, but an improvement nonetheless.

Every time I replace something, the car seems to drive a little better, and the bucking reduced. This problem must be compounded from a lot of little problems.

I'll take a look at the fuel pump/filter next.
 

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Have you checked the IAC (Idle Air Control valve ) yet ? But it sounds like your on the right track . Just thought of this , might want to also check your motor mounts out too.
 

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Discussion Starter · #10 ·
Have you checked the IAC (Idle Air Control valve ) yet ? But it sounds like your on the right track . Just thought of this , might want to also check your motor mounts out too.
Motor mounts have been replaced.

I'm starting to think there is a vacuum leak.

Would you be able to hear a hiss while driving? I noticed, on a quiet street, driving at about 2000 RPM and giving it quarter throttle, I hear a hissing sound.

Another symptom that I didn't notice before, is that after getting back on the throttle after coasting, the car seems to hesitate and buck a little, then set off smoothly.
 

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Discussion Starter · #11 ·
I booked an appointment with the dealership for later this week. The things I've wanted to try fixing seem like a hassle, and as I'm under warranty, might as well try to get it fixed for free.

As a word of thought, another possibility might be that the car is running too rich. I did notice the spark plugs were oily when I took them out, and I smelled gas as I took the intake apart.

I've noticed some bad MPG too. I get about 9.0L/100km on the highway, and 10 in the city. It doesn't matter if I drive aggressively or like a grandma.

As I explained the problem to the dealership mechanic (I spoke to the secretary the first time) he said that my description wasn't accurate to what was written there. There must have been some miscommunication, because even though the new motor mounts helped smooth things over, it didn't exactly fix the problem.
 

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Discussion Starter · #12 ·
Got the car back. Apparantly nothing is wrong, and it's behaving "typically."

I don't agree. Something feels wrong. They couldn't replicate the car having trouble starting, either.

If this is typical with a Focus, I might just go Honda for my next car [shhh]
 
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