Okay
I posted not long ago that I was having a misfire, it was an odd one cause it would only start missing after the engine heated up, when its cold the car drives fine. Members suggested new ignition leads, Im getting around to getting them (dispute with work=less shifts=less money)

But other day was checkin the oil and thought maybe some of the leads under the plenum chamber mught not be on right, so did a quick effort of sqeezing my hand under the plenum to lift the lead closest to the drivers side and I found oil on the connector part of the lead that goes into the spark plug tunnel.

I dunno if this is causing the misfire or its just requires new leads so iam wondering if anyone on the forum has a DIY of removing the plenum chamber. Ive done it once to a commodore but the magna looks a little more complicated adn just wanna make sureabout what im doing. Ive looked for a gregorys at the local spuercheap but they seem to have everyother car except 3rd gen magnas.

Any help will be hugely appreciated.

I have only just removed this 2 weeks ago, You will see five (5) main bolts, three (3) little ones in front, two (02) Big ones on top.... At the back of the plenum there is another three smaller bolts, from memory I think they were a 12mm head, there is one on the driver side right underneath the black/yellow earth wire, the second is in a little further, the third is with the throttle body, althou you might get away with taking this out... grap some rope or whatever you can to hold the plenum up high enough to get ya hands in there...

Have a look at the five (05) bolts that you have pulled out, if they look as thou they are sht get some new ones (local nut n bolt shop have em)... Dont do em up to tight as they will tighten with heat

Workshop Manual:

http://www.lisho.net/?page_id=3

Rob

I had an intermittent misfire on my 3G when I first got the car.
Lead to the fuel injectors was caught under the front corner of the plenum (on the passenger side). The lead is a tight length and it looks like the plenum had previously been removed and pinche the wire. The plastic coating was split from being pinched and when cold it was OK but as the engine heated up it would short the wire to the plenum.

That being said, the plenum is not hard to remove.
Disconnect the air inlet from the throttle body so you can lift the plenum.
1. Front - nut at each end of plenum and two rows of bolts across the inlet tubes.
2. Back - I think about 4 bolts into plenum from brackets next to the firewall. Onebehinf throttle body is a bit hard to see.
3. Disconnect EGR tube from rear of plenum - driver's side. Look out for thin metal gasket and note which way it is facing.
4. Disconnect the air inlet from the throttle body so you can lift the plenum.
5. If you want to remove plenum rather than just rotate it up away from the engine, disconnect the throttle cable bracket at the top of the back of the plenum.

Think that's about it - should be able to lift plenum up now. Just note where the little wiring loom add-on pieces (sensors etc) go that are attached to the bolts across the front of the plenum - no drama but it might help save some time in the reassembly. Also, when lifting the front of the plenum, just take it slowly in case the gasket is old and sticks to the metal. Mine tore the first time I did it but I was able to position the torn bits to get by until I got an insulating gasket from AMC.

Other than that, if no-one else comes back to you in the meantime, I might be able attach a diagram of the plenum but it won't be until late tonight.

once you've taken it off once it won't be difficult the next time.

Cheers.

EDIT: Doh! gazumped.

Yeah, basically Scorpion describe the method very well.

What I did was had a big piece of paper and using my limited artistic talent detailed where each screw, nut or thingy comes from. Would help if you could remove it in a garage when there is no wind blowing away (like when I did mine).

This help me losing screws or going "Hmm, wonder where does this belong?"

Should suggest you set aside a good 4 hours for it. Took me about 6 hrs but I was changing to Barry's gasket kit and fuel rail kit. Also swap my sparkies to iridum. So might want to consider changing your sparkies since you are opening up the plenum.

Hmmm. On my 2'nd Gen V6, the Gregorys manual gives you resistance limits on the HT leads you can check with a multimeter (mine cost about $10 from Dick Smiths I think - a lot cheaper than new leads, and a handy tool to have - especially for wiring stereos and checking switches). Basically, if they're within the limits, then don't bother changing them (unless they're any auto-electricians on here that disagree with me on that point)? No point spending money on new leads un-necessarily.

Limits for my 2'nd gen are:

Leads shorter than 635mm - Less than 30 k/ohms

Leads longer than 635mm - Less than 50 k/ohms

Cheers.

Clarky.

Lead resistance is one way of checking the integrity of the leads. However, it does not replace a detailed physical examination for nicks, abrasion or punchthrough (where the voltage has arced through the insulation, black leads are a BUGGER to see this with).

Cheers
Heath Young

The leads maybe fine but part of my problem is there is oil in the tunnel down the to the spark plug, Im assuming spilt there by the mech who changed out my dizzy and spark plugs. So Im thinking when my engine gets hot the oil is running down to the spark plug and interfering with the spark, so I have to remove the plenum, take out the leads and clena out the tunnel.

i would be checking to see that the tappet cover isnt leaking down the spark plug hole. May just need to tighten down the cover to make a better seal.