When starting up the cold engine, I was surprised how fast the front two air injector pipes got hot compared to the other four. It seems exhaust gases are working there way up the two front pipes rather than ambient air being forced into the combustion products.

I'm wondering if this is a common problem and what might be causing it? I don't imagine the cat is plugged because that would cause all 6 pipes to get really hot and not just the front two.

The cooler areas are clogged. You can take the air injecton pipe off and clean the tubes.

Cheers
DD

Is it normal for exhaust gases to push into the air rail? I thought the idea was for ambient air to be pushed into the exhaust stream to help combust unburned gasoline downstream.

I got the air rail off and did find several of the pipes blocked. The blocks were easy to clear with a thin screwdriver and I verified the open passages with compressed air.

I also noticed that the two of hte six ports in the head were almost completely blocked with carbon. I did clear the passages with a screwdriver, pushing the carbon down into the head.

I wonder if these open ports are facing the back of the exhaust valves which in some cases appear to be built up with carbon. Any harm in spraying some some seafoam or other cleaner into the open ports before I install the air rail?

The air injection system only pumps into the pipe when the engine is cold....I think 157º is the cut-off point....or something like that. A temp switch opens a diverter valve on the back of the air pump which direct pump air into the air filter cannister.

Normal for exhaust gasses to be pushed into the pipes. The main supply pipe has a check valve which prevents the exhaust for going as far as the air pump

Cheers
DD

<shrug>

I don't see any harm in it. Might do some good! The possible consideration I can think of is fouling that cat converter (??).


Cheers
DD

Thanks for the tips Doug,

Job is done with no down side. Engine sounds a little quieter for some reason. Perhaps the air rail nuts are little tighter now. I also verified with a laser temp gun that all the tubs have exhaust flowing into them now.