I have just changed the leads and spark plugs in the car. I noticed when I took the plenum off, the front bank ports on the manifold had a lot more carbon deposit build up than the three rear bank ports. Anyone got any ideas as to why that would be? I have been running platinum plugs all round.

yep the EGR comes in right near the intake, noticed it too on mine and went exploring for the reason

the egr does go into the intake plenum at the back and travels gases thru all cylinders. I have blocked this off too. not sure about that one. thanks tho

It's because the PCV recirculation hose is connected to the intake before the throttle body, so most of the oil vapour will travel down the closest runners after the throttle.

It's because the PCV recirculation hose is connected to the intake before the throttle body, so most of the oil vapour will travel down the closest runners after the throttle.

Yeah but don't the runners alternate between going to the front and rear bank?? If I'm not mistaken, the OP'er is saying that when he took off his plennum chamber and looked into his lower intake manifold - the three ports for the front bank of cylinders had more carbon buildup than the three rear bank. PCV and EGR don't really explain it - because all cylinders should pretty much get the same amount of "carbon buildup" from those two sources.

Tony - have you tried compression checking all cylinders?? as it seems to me to be something related to your front head.

Yeah but don't the runners alternate between going to the front and rear bank?? If I'm not mistaken, the OP'er is saying that when he took off his plennum chamber and looked into his lower intake manifold - the three ports for the front bank of cylinders had more carbon buildup than the three rear bank. PCV and EGR don't really explain it - because all cylinders should pretty much get the same amount of "carbon buildup" from those two sources.

Tony - have you tried compression checking all cylinders?? as it seems to me to be something related to your front head.

You are right, I misread the post. Come to think of it, I noticed that on my old 3.0 too.

Yeah but don't the runners alternate between going to the front and rear bank?? If I'm not mistaken, the OP'er is saying that when he took off his plennum chamber and looked into his lower intake manifold - the three ports for the front bank of cylinders had more carbon buildup than the three rear bank. PCV and EGR don't really explain it - because all cylinders should pretty much get the same amount of "carbon buildup" from those two sources.

Tony - have you tried compression checking all cylinders?? as it seems to me to be something related to your front head.

Exactly, and no i haven't thought of that. Will have to get it done and see what comes of it. thanks

I have spoken to a mitsi tech and as it turns out it is perfectly normal because the front bank runs cooler than the rear.

I have spoken to a mitsi tech and as it turns out it is perfectly normal because the front bank runs cooler than the rear.

Did he tell you why?

Possibly because the front bank gets more airflow?

The Rear bank has the plenum & runners on top of it and that gets hot?

Rear plugs are different (platinums vs regular)?

My guess would be one of these.

Did he tell you why?

yeh as per gas_hed below but the not so much the plugs. The plenum on top and the reduced airflow between engine and firewall makes the rear run hotter. No effects on driving, just one of those things.



Possibly because the front bank gets more airflow?

The Rear bank has the plenum & runners on top of it and that gets hot?

Rear plugs are different (platinums vs regular)?

My guess would be one of these.