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Duratec engine stumble stutter misfire

43K views 57 replies 14 participants last post by  pbfoot 
#1 · (Edited)
UPDATE:
This post was written after I saw my engine stutter problem disappear after replacing a bad PCV hose. The engine stutter problem returned. Replacing the PCV hose did not fix my engine stutter problem. Additional info at post#3.


2004 2.3L ATX with 141K miles.

I do not have a question, but wanted to share a fix and lessons learned.

<snip> …unique problem with engine stutter only between 35 to 45 MPH & only when barely applying the gas pedal. The problem started and was barely detectable and as time went on (and as Arizona temps got hotter) the problem became more prevalent.
In the last couple weeks, this unique problem also started showing up during light acceleration at slower speeds too, and when it happened, the engine stutter also became worse.

Problem has been fixed. I replaced my PCV and PCV hose. The old PCV seemed good, but I replaced it anyway. The old PCV hose looked very bad and seemed to be split, but did not seem to have a hole in it. The hose has two bonded/molded layers. In some areas, the outer layer had peeled away, but the inner layer was still intact. The inner layer was very very soft and was likely collapsing during the engine stutter problem.

The old and new PCV hose had slightly different part numbers and manufacture date differences.

Old: 3S4G-6758-AC
New: 3S4G-6758-AF

Old: >FKM/ECO<03 6
New: >FKM/ECO<13 3

During the work of replacing the PCV hose, I also replaced my lifetime air filter with a stealth CAI K&N cone filter RC-9160. I am mentioning this because this could have played a role in the problem or in the fix-> My intake air vacuum pressure has likely been reduced because of the K&N filter.

On an unrelated note, I also replaced my thermostat, upper and lower radiator hose.

I could not have done this without FF’s. Thank you everybody. [ffrocks]
 
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#3 ·
Duratec engine stumble stutter misfire -NOT- FIXED

The engine stutter I had was there everyday as long as I duplicated the correct scenario (cruise between 35-45mph with light acceleration). Yesterday I did 2 lengthy test drives to (1) confirm proper operation of my brand new thermostat, check temps and adjust coolant level (2) see if the engine stutter problem was gone. It was definitely & positively gone.

Today’s news is engine stutter problem has returned. I am very sorry for my premature announcement that the problem was fixed. I have updated my first post.

I plan to test TPS voltages next, but it might have to wait a few days. BTW, I have recently replaced spark plugs, plug boots, fuel filter and used a can of injector cleaner in a tank of gas.
 
#4 ·
alright.

I'm not sure exactly what you mean by "stutter", but a failed DPFE can cause oscillating RPM's, which can feel like a hesitation. On my Zetec + ATX, it occurred around 2000 RPM. The oscillation itself is small but noticeable; if I had to guess, plus/minus 100 RPM.
 
#5 ·
Two FF’s (amc49 and codices) have PM’ed me on this. Instead of another PM, I am posting my PM reply onto my OP.

Hi guys,
Thanks for your reply. I am unsure if your comments (amc49) were addressed to me or to codices. Not sure how multi/Quotes work in PM’s either. I do not consider my focus problem to be a “misfire” but that word could be used as part of the description. My symptom is best described as 2 separate problems; (#1) hesitation, bog or stumble during light acceleration, a total loss of power/compression-> when at a stop and taking off. I can always recover from this (or prevent this) if I step harder on the gas pedal. This condition is worse or happens more frequent if AC is on. (#2) Surging or bucking <like a bobble head doll> when cruising and barely applying the gas-> This symptom first appeared only between 35 to 45 mph, but has recently also showed up at 15 to 25 mph. I have never seen/felt a problem at highway speeds. Please note that both symptoms above have one thing in common-> happens during light acceleration.

@codices – Like you said, I have never seen these symptoms during my first couple of minutes on a cold engine. I have also seen the symptoms and severity increase "the hotter the car gets"... and more so if during the heat of an AZ summer day. Are you experiencing both symptoms I described above (#1 and #2)?

I had a CEL and P0300 code once and this was before any of these symptoms appeared. I cleared the code and have not seen one since.

Here is a recap of what I have done:
Replaced bad PCV hose. No other vac leaks found/suspected
Spark plugs replaced copper 103’s -gaps set
New fuel filter
MAF is clean and looks new
IACV is clean and I can tell it works based on idle & AC on/off
TPS tests good (full range of motion voltage testing completed)
IMRC solenoids (I have 2 on my PZEV) vac hoses intact and connected to actuators. None of this stuff has been tested or replaced.
Most recent: new set of 4 COPs -coil on plugs & boots

My comments from PM shown below:
I installed my 4 new (COPs) coils ($104.00 via Amazon) a couple days ago. New coils did not fix my stumble/hesitation/bog/bucking/surging problem. With my future plans for this 2004 140K mi car, I am OK with replacing old coils, even if it did not fix my problem. Many many problems <if exactly like this> have been caused by bad COPs. I looked at other Duratec forums (Mazda/Ford truck) and found bad COPs can easily cause this problem.

My next areas of suspicion are; CPS (Cam Pos Sensor) CKP (Crank Pos Sensor), IMRC actuator and solenoid (i have 2 sets of these on my PZEV), Weak Fuel Pump-pressure or Fuel Injectors. 1st up is the CPS and related wiring. I will update my OP-thread about this after my next round... or when I have fixed it.


Thank you for any comments and help.
 
#6 ·
Quick question here. I have a 2005 PZEV Duratec 2.0. Do I have two sets of IMRC actuators and solenoids? Often when I'm accelerating, the car starts accelerating slowly, and then it takes off around 2500 RPM, I bet. I don't have a tach, but I think it's around there. I always wondered if that was normal. Does the intake manifold have something to do with that?

Toby
 
#7 · (Edited)
Hi Toby,

I do not have an answer to your question but let me help remove or add some confusion. The IMRC system has a component that I named "solenoid". I am not sure if the item is properly called a solenoid or not. The solenoid (or two) is located on top of the black plastic intake manifold (IM) and is right in your face after you lift the hood. I also do not know if having 2 IMRC solenoids & actuators is unique to PZEV or not. This old FF picture shows two IMRC solenoids (altho one of them in the pic is mostly hidden by vac hoses) -look at the middle of the picture and find the small copper colored items. Each solenoid has two vac hoses (1) goes into the IM (2) goes to its' own actuator located to the drivers side and mostly underneath the IM.

[/QUOTE]

Also, there is an old thread (or 2 or 3) on FF that talks about engine power loss/slow accel during heat and during loads (AC, lights, stereo). These power losses are/can be normal due to (1) your expectations (2) it's only a 4 cyl Focus (3) engine load (4) other.

My focus is having a problem that is definitely not normal. Your problem might be normal performance under heat/load.
 
#8 ·
05 tumble flap actuators are not the same as the earlier D-tecs. Look under the throttle body on the 05 and you'll see an arm and an electric solenoid. That's the tumble flap (IMRC) actuator.
 
#10 ·
No update. Sorry. Still have the same problem. I have made some progress, but nothing to holler about. I was hoping this thread would hide and no humans would see it until I REALLY found and fixed the problem. Thanks for unearthing this Beyonce.

My current belief, and the item I am focusing in on at the moment is; a bad and semi-clogged-up cat converter. I WILL update this thread within the next 2 weeks.

Sounds like you might have a different engine? -mine is a Duratec.
 
#14 ·
Maybe you should start a new thread? -and provide more details and descriptions of your "hesitation".

What other name or location is the "air bypass valve" that you disconnected?

Maybe take some detailed pics of your engine and post them here? -using host sites like photobucket?
 
#17 ·
Pulling the vacuum hose from the FRPS would NOT be a good fix.

That removes the reference pressure for the pressure sensor, changing normal pressure at different vacuum conditions. (messes up fuel mixture, what it "fixes" at one speed it makes bad at another)

ALSO, if that sensor leaks you'll get fuel under the hood instead of into the intake where it can safely burn.
 
#21 ·
I already changed the plugs, wires and fuel filter.
If you have traditional plug "wires" that = you have a coil pack <<and you do not have a Duratec engine>>. That coil pack is super famous for developing tiny cracks within it and this will cause many kinds of engine stumble stutter misfire problems.

Remove and CLOSELY inspect your coil pack for tiny cracks. Replace it if it looks bad or might be cracked.
 
#20 ·
^^^ Uhm... about 40 to 50 psi. Before I (or others) can help you; please ID your car year and engine type. Also any history of ownership and maintenance done on the car so far? Most Foci have a FRPS that sends fuel pressure to the PCM and the OBD system; and this can be read by most scan tools, so you can see the pressure -assuming the FRPS is not defective.

Separately, you can "tap into" the fuel system and manually measure the fuel pressure using a hand-held pressure gauge. Strangely, I DID THIS and recorded my test results at this thread->
http://www.focusfanatics.com/forum/showthread.php?t=476818

... please go to page 2 and post #13 for the method I used for measuring FP with a hand-held gauge
 
#22 ·
Sorry for the lack of specifics and symptoms on my focus. I am very new to this forum and am trying to come up to speed as quick as I can.
I bought at auction a 2003 focus ZX5 automatic 2.3L. This car sat for 2 years but started up with a jump. I only paid $350 and had hoped to find a low maintenance vehicle that could save me a few bucks. I have two solenoids mounted on the top of the Intake manifold. I swapped the solenoids with each other but no change in the stuttering or shuddering while accelerating. Those solenoids are way to expensive so I'm glad I do not have to replace them (I hope). I did change plugs and coil packs along with fuel filter. The air filter indicator says it's still good but I am looking for a cold intake to replace it. I never heard of a lifetime air filter before this.
I tried my best to spray starting fluid around the intake to see If I could get lucky and find if it had a leak somewhere but no luck. I plan on checking my vacuum with a gauge and then take the intake off to check hose and replace the pcv valve.
What type of scanner tool can read the fuel pressure and sensors? I would like to find a used one on the cheap since I'm just starting to get back on my feet.
I am grateful for your prompt response and any tips you have to offer.
 
#23 ·
Lifetime air filter isn't a worry as long as the indicator shows OK.

You can look at the end of the manifold near the throttle body to see the two actuators for the intake those solenoids affect. Rev the engine by hand in neutral & you can see the actuators move as rpm increases to check operation. Only the back one is monitored for operation by the PCM to show a code when inop. (tumble flaps).

Most important, have you got fresh gas into it?

Add a bottle of dry gas & one of a fuel system cleaner like Chevron Techron to help with the injectors?

Old gas doesn't help with running, you can't figure much until you use that up and at that point the fuel filter should prob. be changed (basic maint).
 
#24 ·
I have changed the gas, added dry gas and changed the fuel filter. The stutter seams to only happen in drive. In neutral is revs up smooth.
I also tested vacuum at solenoid inputs. It's between 20 and jumps to 25 when accelerated. I thought is should go down during acceleration.
I attached the vacuum gauge to the solenoid on the fuel line rail and it read 25 and dropped to zero when accelerated.
The actuators both went in the up direction right after accelerating and then dropped back down... but the actuator nearest the engine block(Swirling ?) seamed to get stuck in the up position after a few accelerations. I shut the engine and restarted and the actuator was back in the down position until I hit the throttle a few more times and then seamed to stick in the up position again. Maybe I should swap these solenoids back to original and check it again.
Why would this stutter not happen in neutral? Could this be related to the transmission? I have flushed the transmission fluid and changed the filter. Could a torque converter or trans solenoid mimic an engine stutter? Or is it under a load when the transmission is engaged thereby asking for more fuel and being starved for fuel or air?
I have an error codes that i may have triggered myself. P0102 - volume air flow "A" circuit low. P2004 = intake MRC stuck open...p0113 = intake air temp sensor high.
I will reset these by disconnecting the battery and see which errors return.
I have also cleaned the maf sensor.
 
#27 ·
Why would this stutter not happen in neutral? Could this be related to the transmission?
The stutter is load induced... on mine. So, the load of the trans, which gear your in, the engine RPM, and other things like AC on or off, helps add to the problem and results in the Stutter.

I have an error codes that i may have triggered myself. P0102 - volume air flow "A" circuit low. P2004 = intake MRC stuck open...p0113 = intake air temp sensor high.
I will reset these by disconnecting the battery and see which errors return.
I have also cleaned the maf sensor.
Yeah, when you mess with the IMRC vac hoses, you set a P2004 DTC. Once the Vac hoses are reconnected and the car is restarted, the P2004 usually goes away soon after. Or like you said, disconnect the battery. This will restart all monitors, so you will have a P1000 Evap Monitor incomplete for several days.

Not sure about the P0102.

The P0113 might suggest an issue with the MAF sensor. Remove sensor, inspect, and clean it with Carb or MAF spray can cleaner. Also, you have a MAP sensor (bottom of intake manifold) but that just does pressure data, not temperature AFAIK. Maybe the P0102 is related to your MAP sensor data; and IF NOT, it should be an error based on MAF data.
 
#26 ·
BTW - that "solenoid" on the fuel rail is actually the fuel pressure sensor. It measures pressure relative to intake manifold pressure rather than absolute. Getting a vacuum reading there would be an accurate place for easy access, just remember that fuel pressure will be affected with that unhooked.
 
#29 ·
I have done a few tests that (almost) rule out some components or some systems; but I have not found the problem.

One important note about my car symptoms are that; it currently has NO symptoms outside of poor MPG. The other symptoms tend to only show-up when it is Hot outside. Higher the temp outside = more likely to see the symptoms.

The next thing I am going to do is:

Remove, test and clean the fuel injectors. Having a pro shop do the testing and cleaning, -because I want it done right, with a fuel injector Test Bench. Another note is, my car is a PZEV and this car has fuel injectors that are unique to the PZEV Focus.

I am also going to re-visit potential sources of Vac leaks.

My suspicion is that I may have 2 items that are broken, or need repair, or need adjustment, or are operating out of spec. Exactly what they are-> don't know.
 
#30 ·
I believe my engine is like yours, a PZEV. It's a 2003, 2.3 liter with 155k miles. I did not know what PZEV meant. PZEV = Partial Zero Emissions vehicle. From what I'm reading it is one of the cleanest (if not cleanest) running engines without significant (if any) power loss. That makes my daughter happy knowing it's a green eco friendly car but it is also why it is a complicated system. I'm with you thinking there could be more than 1 problem causing the stuttering under load while accelerating. I like your idea of cleaning the fuel injectors. Maybe under a load they cannot keep up with demand. I am very curious why this car sputters under load but in nuetral has no sputtering. While I wait for parts to take off the intake manifold, I will try the same as you and clean the fuel injectors. I see a few videos on youtube showing how to do this.
Do you think at 150k miles that the spring holding tension on the timing chain could be loose?
 
#31 ·
I believe my engine is like yours, a PZEV

...

Do you think at 150k miles that the spring holding tension on the timing chain could be loose?
PZEV Foci have red colored fuel injectors. Not perfect red, but red-ish.

I have only seen a couple threads about the chain. I can not give you any solid advise on the chain, I have no experience messing with it. Outside of some kind of strange chain ticking or slapping noise, there is no reason to suspect your chain tension is bad. If you have a valve cover oil leak -and- are going to replace the valve cover gasket; that is your chance to get your eyeballs and fingers on the chain for inspection. You will only be able to see a small portion of the chain, but you should have enough room to see if the chain has any issues or excessive slack.
 
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