[suby6]

Have an 03 Zetec manual trans
Last summer it started having intermittent hesitation problems.Generally happens in any gear with light throttle mostly around 2000 - 2200 Rpm. Can sort of hear the engine missing or something when it happens. Seems to mostly do it when you take your foot off the gas and then reapply it lightly. Sometimes will do it a lot sometimes not at all for a couple days. Can also get it to do it at a stop in neutral with light throttle and that rpm range.

Here is what Ive done trying to fix it:
* Tried a different coil pack. Didn't fix so put the stock one back in
* New copper plugs gapped to .050
* Replaced ignition wires as one of my massive speed wires broke with all the messing around. Now cheap 8mm champion wires
* Replaced valve cover gasket. Though was really just leaking on the outside of the engine not in the plug wells.
*Tried some data logging but don't know what Im doing. Chose any sensors related to spark, fuel, or ignition. No problems found that way and ecu no codes.
*Replaced fuel filter and PCV valve
*New O2 sensor. (Upper. Lower is disabled.
*EGR disabled through tune.
*Reverted tune to stock. Still hesitates
*Replaced coil pack harness the year before.
*Replaced alternator and battery the year before. Electrical seems fine.
* Vacuum hoses and PVC hoses seem fine. No leaks found with carb cleaner test.


Whats next? Any suggestions on things to check? Driving me crazy..
Thanks for any insights.

Dion

 

[freemind]

Check the coil for any large or small cracks.You have to remove it to inspect correctly.
Did you replace the coil pigtail with a new or used one?

Zetecs really like a gap of .055

 

[amc49]

A measly .005" difference in gap will go right past the motor; it will not notice it. I set mine intentionally too close to let the wear sweep past optimum last longer. Works fine and forever.

Could possibly be a wear issue with the TPS switch.

 

[DognamedMack]

DPFE?
Dirty Throttle body?
Buddy once had an ear brake off a newish spark plug while it was in the motor.

 

[suby6]

Thanks guys. Already tried swapping the coil for a day with a new after market. Still hesitated so put the stock back on. Replaced its harness with new.

Tried cleaning throttle body but not IAC. Could IAC cause issues besides idle? Generally it idles well.

EGR disabled through tune so that rules out DPFE right?

Was wondering about TPS. Will pull one at a wrecker when I have some time. MAy also take it to a shop and have them scope it or something.

 

[amc49]

EGR disabled says nothing to the valve possibly leaking slightly anyway.

 

[Leora83]

How good a job did you do splicing in the new coil harness?
I tried to do a quick-and-dirty job on mine because of the unreal cold, and within six months I was having the same issue. Took it apart, soldered properly like I should have the first time, heat-shrunk it back up, and it's been fine ever since.

 

[Mandroid]

You checked for codes right? I'm sure you would have noticed if you were into tuning. As other have mentioned, the TPS could have a dead spot but that would usually present itself much more obviously. As AMC said, the egr valve could be leaking. How many miles? When was the timing belt replaced?

 

[Mandroid]

You can also do an air pressure test to see if the cat is bad

 

[suby6]

150,000km / 93,000 miles

Coil pack harness was connected with crimp connectors and shrink tubing that came with the harness from the dealer. Guess I can redo with solder instead.

Timing belt hasn't been done. Could that cause intermittent issues? I would think timing would be more consistent.

Cat is compact style magnaflow metal core welded in after the flex pipe. Approx 50,000 km on it. (Long tube header)

Can I rule out the EGR valve easily somehow?

 

[amc49]

Uh, thinking..................pull hose to the GR valve and then hook a vacuum gauge to valve with motor running at idle, if leaking you should get some vacuum there. Should be none.

 

[Mandroid]

150,000km / 93,000 miles

Coil pack harness was connected with crimp connectors and shrink tubing that came with the harness from the dealer. Guess I can redo with solder instead.

Timing belt hasn't been done. Could that cause intermittent issues? I would think timing would be more consistent.

Cat is compact style magnaflow metal core welded in after the flex pipe. Approx 50,000 km on it. (Long tube header)

Can I rule out the EGR valve easily somehow?

We can rule out timing and cat then. AMC has good info on the EGR test. Did you check the PCV valve and/or hose?

 

[BigRandySasquatch]

ok so im new and I just found this post .. having an identical symptom. Light rpms , stuttering at cruise speed. I just got my focus last week and I didn't notice the problem durrring the test drive. Glad I found this site! Ill be trying the EGR vacuum test this weekend Thanks guys

 

[suby6]

Thanks guys will take a look at the egr. Don't have a vac gauge but maybe I will be able to feel it or have it suck in some cleaner.

Big Randy if yours is stock it may be your dpfe or whatever it's called. It's the box the hoses go to on the firewall by the egr.