My 01 VW Jetta with 181690 miles started having intermittent loss of power a year ago:
it never conks out; 2) it loses power on the highway at 70 or in town at 25; 3) engine is usually hot, about an hour into a trip, but now does it cold, too; 4) weather doesn’t matter: dry or wet; 5) check engine light flashes while it happens 6) it feels like it’s running out of gas but isn’t.
Mechanics have tried the following: Note: every time I brought it in to be looked at, the symptoms above were happening
1)March 2013: replaced coil pack and it ran fine until Sep; 2) Sep 2013: ran Dx on check engine light: “arching all over the place” so replace spark plug wires; 3)dec 2013: got oil changed 4)Jan 2014: ran Dx and was told crack in piston; 5) Jan 2014: got second opinion and told wrong spark plugs were used (single electrode vs triple electrode)-replaced all spark plugs; got car inspected and had oil changed again as it was dirty; 5)feb 2014 mechanic is stumped, but found an article about clean oil and changed the oil again. Oil was down almost a quart.
You said it ran fine between March and September after replacing a coil pack. Those VW coil packs were notoriously bad. I would suspect another bad coil pack. When they heat up is when they begin to fail, then they fail even when cold, with misfires that cause rough running, loss of power, and the check engine light coming on.
There was also a “silent recall” on the mass airflow sensor (MAF) on that model/year, so that could also be a possibility.
There should be a stored code in “P0123” format. Post it here if you have it.
By the way, using the wrong plugs can sometimes damage coils, so perhaps the wrong plugs you were using damaged the new coil pack.
Thank you @jesmed! I appreciate your response. I will look at the paperwork and notes I took w/mechanic for the codes and get back to you. I will also look into the silent recall as I’ve had that code show up in the past but don’t remember if I had it addressed.
I think the VW extended warranty on coils was for 7 years/70k miles so you’re likely out of luck.
It might be noted that coils are often killed due to aged spark plugs, misfires due to whatever reason including moisture on the coil terminals/plug wells, etc, etc.
To me anyway, it’s ill-advised to change coils without changing spark plugs as a new coil can be damaged by an old plug. In a nutshell, changing the coil is working on the symptom, not the cause.
An intermittent loss of power can also be caused by a failing fuel pump. This will not set any codes and can certainly be a fine one month, bad the next, fine the next minute, and so on.
At 181k miles an iffy fuel pump would not surprise me; especially if the fuel filter has not been serviced regularly.
@ok4450: thank you for the additonal plug/wire/coil informantion, and your suggestion regarding the fuel pump. I’ll look through my records to see when/if it was replaced. Fuel filter has had regular upkeep.
@jesmed: the codes were as follows: P0301 misfire cy 1; P0300 multiple misfires; P0304 misfire cy 4. Notes from Dx: trbl shoot misfires 1 & 4: remove intake plenum and perform cy compression test. All 4 cy at 175psi.