mc_renn

Hi Everyone -

I want to change the plugs on my 91 C4 and was surprised I didn't find any good DIY's here on rennlist. I will attempt to do it once I get enough info and will document it here via pictures.

So my first question - what stuff do i need to get out of the way to get at the plugs? how difficult is this? what spark plugs should i use?

Thanks!

Makmov

Its not hard. its more what tool you use on the top side. The bottom is easy access, and most of the top is too. There is a couple that are a little tricky to get at. The Porsche tool that comes with the car works pretty well otherwise you just need to come up with the right extension, and I use a wobbley, and a short ratchet handle with a swivel head. The hardest one under the power steering pump


As far as what is need out of the way, the airbox cover and filter on the pass side and the blower motor box on the driver side. Bosch FR-5-DTC

Silvertarga

A magnetic spark plug socket is helpful and if you dont have that a one of those mechanical claws to fish out the spark plug that your will probably drop in the hole, mak is right the one under the PS pump is difficult without the oem tool

bmohr

anyone have the torque values off hand on the spark plugs? One of mine wiggled out after my last valve job/spark plug job.

BigMikeATL

You may as well adjust the valves if they haven't been done in a while.

Rocket Rob

Spark plus should be torqued to 20-30 Nm or 15-22 ft-lbs

SuperUser

Quick questions, how much of that dielectric grease should be applied to the plug boots. The tube I got from Pelican is very large, it must be a lifetime supply for a shop.

BoscoBilly

Strange... i always thought that you had to remove some motorplating, heatshields, Cat and stuff... in order to reach the sparkplugs. Never done it before on my C2 though... just on my 79 SC.

bmohr

Thanks RR, much appreciated. Yes, valves are going to be done at the same time. Maybe wires too.

Rocket Rob

Yes, you need to remove the cat, heat shields and secondary muffler to access the plugs on a 964.

Rocket Rob

FYI - Changing the wires with the engine in the car is a pain. The tricky part is where they are clamped to the fan housing underneath the intake manifold. It can be done. My friend and I did but..... You may want to consider loosening the intake to raise it up so you have some room to work.

Vandit

Just to confirm, you do not need to remove the side engine tins?

Rocket Rob

I remove the engine side tins to make better access to the top plugs. Could it be done leaving them in place? Perhaps but I've always removed the tins because I change my plugs when I'm adjusting the valves.

tbennett017

+1 ^ I remove the tinware when I do the valves/plugs, as it just makes it a lot easier. I also take the opportunity to scrub and maybe repaint the tins too... just to keep it tidy. I use a battleship gray paint so I can see oil leaks or stains... good early warning of problems.