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Hi Guys,

Apologies for the extremely long post in advance! Long time lurker, decided to make an account finally because I'm really lost when it comes to what to do next.

I own a 2004 ZX5 SVT w/ 161,XXX. After refreshing my front & back suspension about 4 months ago, my car started misfiring. Took it into my local mechanic, and he determined it was misfiring due to oil from the valve cover gasket seeping into the spark plug wells. $1500 later, we replaced the valve cover gasket, all spark plugs, all spark plug wires, and the entire PVC system ($500 from Ford!) Hoping that would fix it, my problem still persists. I noticed the VCT sensor was leaking as well, but he told me it's only leaking from the bottom O-ring and shouldn't affect my spark plugs at all (though I always see a small pool of oil where the sensor meets the cover on top). Before we began replacing anything, I asked him about the coil and he informed me they rarely go out, so I disregarding that suggestion.

Hopefully if I explain what I experience in the car, maybe that will help? So here's how it goes: While in any gear under load whether it's straight from a dig or going 75mph in 6th on the freeway, if I apply any throttle especially during WOT, my car starts to literally hiccup. The best way I can describe it is it feels like fuel is being cut off somewhere. It gets so bad that sometimes it will misfire 3-4 times in a row and mimics the sound of me hitting the rev limiter, and my car starts to vibrate pretty bad to the point where it feels like I have a broken driver side axle. I'm not necessarily sure if that's a misfire or not since I don't have a CEL from it.

Basically I'm at a point where I'm lost what to do next. Even my mechanic doesn't know. I've been doing a lot of reading on the forums, and I haven't seen anyone describing the same issues I'm having. Should I try replacing the TPS? I've already changed the fuel filter which I'm sure helped but didn't fix the problem. I believe the fuel pump is good, since it always primes as soon as I put the key in. I'm really contemplating replacing all of the fuel injectors since they're 10 years old with 10 years worth of crap built up.

Thanks guys, and sorry again for the long post!
 

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Coils are maintenance items just like spark plugs on these. Pull it and look for very small cracks, you'll find them and common. Coil is dead if cracked. The connector can crack wires in it to show problems too.

In no way would I consider $1500 well spent with what you did there...........

Fuel pump shows up bad under load, priming instantly means nothing in that. TPS generally shows bad at idle first since the throttle stays there to wear it out the most time wise.

Replace injectors for missing? Nah, I haven't replaced a one on any car I've ever had for 30 years and with many times misfiring, I always find the problem to correct it.
 

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Discussion Starter #3
Thanks for the reply amc49.

Coils are maintenance items just like spark plugs on these. Pull it and look for very small cracks, you'll find them and common. Coil is dead if cracked. The connector can crack wires in it to show problems too.
I'll be bringing my car into the shop on Saturday morning to have them look over this.

In no way would I consider $1500 well spent with what you did there...........
Agreed, but I was in a bit of a pickle as this is my daily driver.

Fuel pump shows up bad under load, priming instantly means nothing in that. TPS generally shows bad at idle first since the throttle stays there to wear it out the most time wise.
Ever experienced a fuel pump issue on these cars? Now that I think of it, the fuel pump may be the issue because for awhile now, I have to slap the crap out of my gauges because the needle for fuel never moves up. Only happens when it's 80+ degrees outside.

Replace injectors for missing? Nah, I haven't replaced a one on any car I've ever had for 30 years and with many times misfiring, I always find the problem to correct it.
That's what I figured, which is why I didn't bother jumping the gun and purchasing all new injectors right away.
 

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Vince your Moderator
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amc is right.
 

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I have replaced one injector, but it was dumping too much fuel and didn't cause a misfire. It just made fuel economy crappy. It was also a different vehicle, ran kinda crappy before it was warm, and would flood on startup sometimes.

Have you scanned the car for codes? Does the misfire cause the CEL to flash?

I bet you get a lean code, and I bet I can tell you how to fix it yourself.
 

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Vince your Moderator
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Now you have two of the smartest guys on the forum helping you!
 

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'Ever experienced a fuel pump issue on these cars?'

Yes, on 3 of them. It shows up under load when fuel demand is the highest, idle has virtually no fuel demand at all. Same as old school mechanical pumps that were motor driven. Pay attention to fuel level in tank, if lower than 1/4 can give trouble if the pump pickup strainer is clogged, common on these and horrible in the '00-'02 models. Pump pickup area was modded after that and better but if ethanol laced fuel used in your area then pump clogging is always a potential issue as the ethanol brings in far more water based crap that clogs things up. Man's best friend that stuff is....................you often cannot rely on big business to keep the fuel as clean as it needs to be, they are far more worried about not being able to pay the CEO enough.

Or pump working fine one second the next it's dead and doesn't work at all. Again often tied to ethanol corrosion which eats the paint insulation off pump armature wires until it shorts out suddenly. The p-sser is when one does that and then comes back to running OK for a week or a day and then does it again, that one can throw you for a bit. Had that happen once. Car idling then goes to pure crap and dies and no pump noise. Then when it cooled off back to working like normal but then does it again later. The key is listening for the pump spin-up at key on, if nothing change pump even if it goes back to working. It WILL do it again.
 

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Simple answer, find a new/better mechanic.
As noted, $1,500 seems out of line for an oil leak, which you still have; and a misfire you still have too.

IMO, it really does no good for any of us to shoot out ideas. You aren't the one fixing it and I really doubt any mechanic will give you a discount if this is what the internet said is wrong and needs to be fixed. We're not here to tell anyone how to do their job.

But maybe a better question is what are you considering a mechanic? If it's the local oil change, tire and exhaust shop ... I'd have to guess that they aren't employing a seasoned mechanic that would know cars better than someone fresh out of high school or tech school.
 

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Discussion Starter #10
Thanks everyone for the replies. Here's what I've gathered:

Have you scanned the car for codes? Does the misfire cause the CEL to flash?

I bet you get a lean code, and I bet I can tell you how to fix it yourself.
Before we did the $1500 in work, I did have a CEL and it pulled the code which was leaning out (forgot what code exactly it was). Once he performed those repairs, the CEL was cleared and hasn't came back since.

I am assuming that your mechanic did fix the things that he worked on---- however, there is always the VCT oil ring problem. We can tell you how to fix that too for about $5.
That would be awesome! I wasn't sure if O-Ring's were available for that sensor. Again, did some reading on the forums and saw mixed answers.

Or pump working fine one second the next it's dead and doesn't work at all. Again often tied to ethanol corrosion which eats the paint insulation off pump armature wires until it shorts out suddenly. The p-sser is when one does that and then comes back to running OK for a week or a day and then does it again, that one can throw you for a bit. Had that happen once. Car idling then goes to pure crap and dies and no pump noise. Then when it cooled off back to working like normal but then does it again later. The key is listening for the pump spin-up at key on, if nothing change pump even if it goes back to working. It WILL do it again.
Almost to a T what happens. Seems to run great in the morning when it's 60 degrees outside on the way to work. Then I take it to lunch in 90+ degrees and it runs like crap, misfiring 3-4 times in a row whether I'm barely giving it throttle or going WOT on the highway.

Simple answer, find a new/better mechanic.
As noted, $1,500 seems out of line for an oil leak, which you still have; and a misfire you still have too.

IMO, it really does no good for any of us to shoot out ideas. You aren't the one fixing it and I really doubt any mechanic will give you a discount if this is what the internet said is wrong and needs to be fixed. We're not here to tell anyone how to do their job.

But maybe a better question is what are you considering a mechanic? If it's the local oil change, tire and exhaust shop ... I'd have to guess that they aren't employing a seasoned mechanic that would know cars better than someone fresh out of high school or tech school.
I apologize, I should have clarified. I'm only looking for guidance because both my mechanic and I are at a fork in the road. I definitely won't be showing up at his full service shop saying "Well the internet says this is the problem, offer me a refund." I have no intentions of getting a discount, refund, etc. I paid him for the work we agreed upon to fix, so I have no issue with that. My only issue is that we're stuck and I'm curious if I'm on the right track. Which AMC is leading me to believe it's the fuel pump.

I guess my next question is, is there any real way of testing a fuel pump, or am I SOL and better off replacing the damn thing?

Thanks again guys!!
 

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More Focus experienced heads have chimed in already, I'd suggest looking a amc's first post mentioning the Coil before guessing at anything more involved/expensive.

A scan tool can tell you fuel pressure as you drive, and would be a great way to check that before guessing that the pump can't keep up on occasion. (My Harbor Freight one at around $100 when I got it has been invaluable - second cheapest they had avail. and it does more than just scan codes)
 

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More Focus experienced heads have chimed in already, I'd suggest looking a amc's first post mentioning the Coil before guessing at anything more involved/expensive.

A scan tool can tell you fuel pressure as you drive, and would be a great way to check that before guessing that the pump can't keep up on occasion. (My Harbor Freight one at around $100 when I got it has been invaluable - second cheapest they had avail. and it does more than just scan codes)
Appreciate the feedback, Sailor. You're absolutely right about starting with the least expensive first. Just an FYI, I did have a chance to look at the wiring leading to the coil. I did not see any exposed/damaged/frayed wiring, or cracks for that matter.

However.. I did see on the wires leading to the VCT sensor that some of the insulation was missing, exposing the copper wiring. Didn't look like it was an issue though, since I haven't gotten a CEL or any issues. I'm guessing I should probably wrap some electrical tape around that..
 

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When you get a chance, for a double check on the coil you have to remove it. We've seen a lot of cracking noticeable from the top recently, but historically it often showed first on the hidden bottom.

I might guess that as they are getting older the housings are becoming more brittle, the epoxy filler was where the problem first surfaced. Total guesswork on why the outside seems to show more issues lately.
 

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When you get a chance, for a double check on the coil you have to remove it. We've seen a lot of cracking noticeable from the top recently, but historically it often showed first on the hidden bottom.

I might guess that as they are getting older the housings are becoming more brittle, the epoxy filler was where the problem first surfaced. Total guesswork on why the outside seems to show more issues lately.
I believe I'm just going to have it replaced regardless, since it's not an expensive part. Since I didn't see any issues with the actual pigtail harness, should I order a replacement one anyways? It's only $42, and I'd rather order one now and not have to replace it later down the road.
 

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Personal preference on that.

I wouldn't replace the pigtail myself unless I saw a reason for doing so.
 

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Personal preference on that.

I wouldn't replace the pigtail myself unless I saw a reason for doing so.
Thanks for the advice Sailor. I'll be ordering a replacement coil tonight. Will let you guys know how it goes in the next couple of days!
 

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The coil gets replaced just like plugs (more often actually in some cases, one car I've got has had 3 now) and is a normal maintenance item, although I feel they could make them better than that. Four coils though in that small package; gonna get kinda hot there.

Look CLOSE at the coil connector, the wires can break up just INSIDE the plastic housing and if just casually handling it you will NOT see that, BTDT.
 

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I've yet to have a coil go bad but that's me. What caused jerking in ours was the hose off the pcv valve would collapse only when it got warm.

The newer hoses were redesigned to not collapse, so if yours doesn't have a thick tin foil protecter around it then I'd replace it any way, $43.00 part from dealer. 5-30 minute install.

My second move would be to clean the strainers off the fuel pump as this was said I think.
 

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The coil gets replaced just like plugs (more often actually in some cases, one car I've got has had 3 now) and is a normal maintenance item, although I feel they could make them better than that. Four coils though in that small package; gonna get kinda hot there.

Look CLOSE at the coil connector, the wires can break up just INSIDE the plastic housing and if just casually handling it you will NOT see that, BTDT.
Thanks for the advice amc. I will definitely have my tech look at all wiring tomorrow when doing the install. Coil should be here tomorrow in the late afternoon!


I've yet to have a coil go bad but that's me. What caused jerking in ours was the hose off the pcv valve would collapse only when it got warm.

The newer hoses were redesigned to not collapse, so if yours doesn't have a thick tin foil protecter around it then I'd replace it any way, $43.00 part from dealer. 5-30 minute install.

My second move would be to clean the strainers off the fuel pump as this was said I think.
Thanks for the heads up rhowe. When I ordered the entire PVC kit from Ford, I'm pretty sure they sent me their most updated parts. I personally didn't see any kind of tin foil on the hose, but then again I wasn't doing the install. I'll definitely bring it up tomorrow at my shop though.
 

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I would also reccomend learning to work on your car if you are capable. Save yourself a lot of money.
 
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