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Gas pedal vibrates when accelerating + uneven power (after new sparkplugs)

5529 Views 5 Replies 4 Participants Last post by  mikefl
1.8T 2002 AWM 123K.

Last week I changed the sparkplugs to NGK BKR6E and gapped each one to 0.032. Use 20ft-lbs torque.

[Previously indy had installed Autolite sparkplugs, which when I checked, were gapped at at different settings from 0.035 to 0.045 all with different torque, the plug that was nearest to the firewall had rust on the head]

After the changing the sparkplugs the car accelerates very fast from stop with the same amount of pressure on the pedal. It does that sometimes and accelerates normally at other sometimes.

Also I noticed that when I press the gas pedal halfway down to accelerate faster, I feel the vibrations on my foot. The vibration on the pedal was not there previously with the old junk sparkplugs.

Can you experts share your thoughts with the following:

  • The reason for the vibration on the gas pedal
  • The reason for the uneven acceleration
  • I gapped it exactly to 0.032. The coin-like gap tool had to be pulled out of the gap at 0.032. Is this the correct way to gap them?
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With fly-by-wire electronic throttle there is no physical connection, so don't know what to say about that...just where you're feeling a real vibration.

Any CEL, codes ?? If you get a misfire code, switch that coil with another cylinder, to see if misfire moves there...if so, replace that coil.

If no codes:
I would still look to the ignition coils....

-Look at the rubber sleeve on each for ANY cracking, holes or separation...would short to engine head and cause misfire.

-Check all coil connections...output stage connecters.

-Make sure you didn't disturb any fuel injector connections either.
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The vibration is felt on my right foot that is pressing the gas pedal.
The ignition coils were replaced by my POS dealer in Feb this gear under recall.
CEL is not on but I will get it scanned.

At 123K it's still on original engine mounts and tranny mounts so that may have something to do with this.
It's possible that the mounts are shot and the extra power of a properly tuned engine is making the flex enough to vibrate.
If the mounts were bad I would think you'd feel a vibration in the steering wheel as well. Or at least the floor near the pedal.
That's next on my agenda after I fix my driver window issue. :)
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