I had my engine rebuilt, since reinstalling it, it runs very very rich at idle. i had the motor scanned found a bad map sensor, havnt run the boat yet since replacing it, the scan showed the IAP number i believe it was at 140 at idle thru 3000rpm then fine 150 from 3000-wot. does anyone know if the map sensor would cause this or do I have another issue?

also on a side note the starboard header when starting up puts this milky brown haze in the water. its not oil i have checked several times.

the bad map can cause to run rich, but those engines were known to be very rich stock, also if you changed something in the rebuild(cam, compression, etc) will effect the ECM as well..

Yea I changed the cam and also put headers on, the ecm was sent out to be reprogrammed by an expert in tunes in Kentucky I think

1) What is your basis for saying its rich? Wide band? Plug readings? Exhaust smell?


2) What does the AFR read if so equipped?

We need more data. There were a lot of things changed without baseline data to compare against. Fix the MAP sensor and let us know the results.

Bottom line is if the MAP sensor is throwing out bad data then the ECM will read the 'wrong' cell for applying fuel, spark etc. In layman's terms it will rung like s$%t.

so what you have now is SWAG...scientific wild ass guess...

Milky Brown haze in the water at start-up does not sound good.... I am guessing oil and water mixing where they are not supposed to....... maybe some reversion or a leak into the exhaust port.

I did replace the MAP sensor, didnt help the issue, to answer ? 1 you can smell gas at idle and there is a sheen behind the boat. I did find out however the headers are leaking back after shut down was having difficulty starting the boat after running it thought was a fuel psi problem but last time out I drained the header as soon as i stopped and when I went to leave several hours later the boat fired right up. At this point I think it maybe a fuel injector issue but not certain yet.

found headers to be leaking water after shut down, thankfully never reached the oil.