Spark Plug Changeout 05 GTX 4-Tec

LCDRChemEng · 10-29-2009, 09:14 AM

I hope this is not answered anywhere else, I've searched everywhere and can't find any reference to this.

I'd like to change the spark plugs on my 05 GTX 4-tec 155. I've noticed some hesitation when under part-throttle, normally around 5000 RPM. The engine seems to surge and the revs fluctuate about 100-300 rpms. I just relined the jet pump and the impeller is flawless, so cavitation is not an issue. I figure it's time to change the sparkplugs, but I can't even spot them under the shroud.

The owner's manual says this is to be done by the dealer, but I figure this would be a good place to ask for DIY opinions. Any advice is much appreciated.

faster7581 · 10-29-2009, 10:31 AM

remove the 4 10mm bolts that hold the big black plastic platform for the seat latches, unhook the coolant overflow and rest in the hull.. pull out the oil dipstick, remove the black plastic shroud covering the top of the motor, there is a tab on the front and rear.... unplug the coil packs and pull them out, the plugs are DCPR8E, remove with 5/8 socket, you will have the remove the tops of the new plugs most likely, they just thread off, you ll see if you compare tops the the original ones.. install in reverse order..

LCDRChemEng · 10-29-2009, 10:35 AM

Many thanks, Faster, I'll try it today.

LCDRChemEng · 11-02-2009, 09:35 AM

Ok, I was able to replace the sparkplugs with no problems at first. I did, however want to post an advisory to anyone else reading this thread.

The coil pack connects to the spark plug by means of a tube (or "pipe") within a thin plastic sleeve. The pipe/sleeve goes through a soft rubber grommet on the head cover opening onto the sparkplug.

After disconnecting the coil plug and pulling the pipe off the plug, remember to lubricate the sleeve with 10-40 oil. Without lubrication, the sleeve is liable to stick to the grommet and remain in the opening after pulling out the tube. Once stuck it will NOT COME OFF. I found out the hard way when removing the spark plugs a second time for winterizing.

cole30 · 06-07-2010, 03:16 PM

Did changing the spark plugs fix the problem? I am having the same kind of issue with my 2002 GTX 4-Tec.

LCDRChemEng · 06-07-2010, 03:47 PM

Yes, after changing the spark plugs the engine responded smoothly and strongly. Be sure to grease the pipe, though, I had to order new coil packs because the plastic sleeve got stuck good and tight and had to be torn out.

cole30 · 06-07-2010, 04:29 PM

Thanks! I'll change the plugs in mine and see if that fixes the problem.