6.2 mpi high iac count

[tep59]

Recently purchased a 2003 6.2 mx serial #0m094440. It had 2 mushroomed valves and I was told that. I had the heads fixed and put it back together and bolted it down to a large dolly to give a test run. It cranked wright up but after setting time it is running a little rich and is turning plugs black. I have checked grounds and many other circuits many times and found no bad wires. I also checked for vacuum leak could not find one. Have replaced map, coolant, air temp, tps, knock sensor and iac motor. With scanner on it warmed up the only thing that seems to be out or range is the iac count at 140 and the injector pulse with at 3.5. I also replaced the fuel pump and regulator. pressure is about 22lbs at idle. witch is about wright from all I have read. I replaced the iac twice. Any clues. Thanks

 

[alldodge]

Recently purchased a 2003 6.2 mx serial #0m094440. It had 2 mushroomed valves and I was told that. I had the heads fixed and put it back together and bolted it down to a large dolly to give a test run. It cranked wright up but after setting time it is running a little rich and is turning plugs black. I have checked grounds and many other circuits many times and found no bad wires. I also checked for vacuum leak could not find one. Have replaced map, coolant, air temp, tps, knock sensor and iac motor. With scanner on it warmed up the only thing that seems to be out or range is the iac count at 140 and the injector pulse with at 3.5. I also replaced the fuel pump and regulator. pressure is about 22lbs at idle. witch is about wright from all I have read. I replaced the iac twice. Any clues. Thanks

Fuel pressure is way low for the 6.2 from Merc manual 31. Manual indicates it should be 43psi at 1800 rpm. While 1800 is not idle, 22 psi looks real low.

Mushroom valves is an indication of to much heat usually caused by engine running to lean.

 

[Fun Times]

Hi there, welcome to iboats!

Actually 22 PSI is to low on the fuel pressure, it should more around 30 PSI. But your injector plusewith is much to high, it should be more in the low 2.0 to high 1.9 range. And 140 is to high for the IAC. While sometimes the IAC numbers are all over the place 40 is a set goal to try and achieve all at idle RPM.

You may want to run a engine vacuum test to see what the condition of the engine is in "mechanically wise". A compression and leak down test won't hurt much either.......Once it's physically done that is.

The 6.2's do seem to kind of have a common issue with bad valves and intake gasket leaks to where It reminds me of a few interesting problems like this one for example.

http://forums.iboats.com/forum/engi...gines-outdrives/322189-fuel-pressure-bouncing

Once you know the engine mechanical is 100% good......Then I would start to suspect an ECM problem. MEFIburn.com may be able to do an inspection for you.

http://mefiburn.com/mefiecms.asp#merc

Hope it's something simple, good luck.

 

[tep59]

So here is a little more info on this engine, the intake and all the fuel parts, electronic and electrical parts including computer came off a 2003 6.2 and basically the long block is off a 2004 6.2. I also did a compression and a vacuum test and all was with in specs. Thanks for the welcome and info.:faint2:

 

[tep59]

from a cold start on these engines is the rpm higher briefly then down to it's normal warm rpm idle?

 

[Fun Times]

from a cold start on these engines is the rpm higher briefly then down to it's normal warm rpm idle?

Yes it should be around the 750-775 rpm range cold and slowly go down to 600 rpm by 154+ degrees. But the most important thing you should be doing upon starting the engine is checking to see if the engine rpm is rising up to 800+ rpm to excite the alternator in order for it to start charging properly. Also 1300 rpm is the recommended idle speed during warm up especially when using a flushing attachment.

http://www.boatfix.com/merc/Bullet/99/99_09.pdf