Backpressure issue

caylorray

Recruit
Joined
May 31, 2008
Messages
2
My 04 Suzuki df90 has a backpressure problem.

Sitting in the water or lower unit in a tub, it runs sluggish at idle and eventually dies. Above idle it seems to run fine. Let it sit a bit and it fires right back up. Sometimes get a check eng lt (3,2). I was told, maybe on this site, this pattern indicates MAP sensor.

Using water-inlet muffs, the engine runs perfect.

The research I've done suggest a backpressure issue. I don't know what could cause a backpressure problem, but I have seen mention of a blown gasket somewhere in the exhaust system. Although I can't seem to find where any exhaust gaskets might be looking at my parts book.

Oh, the engine has close to 600 hours. Only maintenance that's been done is routine. No indicators leading up to this starting to happen.

What might be the most probable cause?
 

caylorray

Recruit
Joined
May 31, 2008
Messages
2
Re: Backpressure issue

Just ran it again with the lower unit in a tub to try something. Took the top eng cowling off and the slight hesitation/roughness went away. Put the top back on, and it came back.

Don't see any air intake restrictions, at least from what I can see without take components off.

Can a bad MAP sensor cause all these symptons, or are there other things I can look at? What are the odds replacing the MAP sensor will cure all?
 
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