'03 225 efi running rich at idle.

[FeFanatic]

0T749027 it's a 225 efi. I have had issues with it wanting to load up at idle in gear and die. This week it seemed to be worse than before.
I have an early Mercury DDT that I can monitor data and codes. I also have Smartcraft gauges that I monitor.

This motor will idle all day long as long as it is in neutral. When it is put into gear it will idle, start loading up slowly, and die unless I put it back in neutral or give it throttle.

Checking with the DDT does show the tps at .495 at idle. Press the throttle and let it go back to idle and it might be at .230 the next time. I know that is still within spec for idle but am thinking the tps may be a little erratic.

A month ago I discovered the wheel that operates the throttle cam was flat on one side so I replaced it. The air gap on the linkage is at .020.

The thing screams at full throttle and mid throttle performance is good. Just idle in gear.

Fuel pressure is in spec and does not leakdown. New plugs.

So, I ran it hard, headed back to ramp, and let it idle in gear until I got to the ramp and let it die on its own.

Pulling the spark plugs showed starboard cylinders dry but black sooty. Port cylinders were wet (not extremely) and black. This is indicating a rich condition.

I've checked the mechanical (pulse) pump and I was pumping the bulb when it was acting up and there was no change.

Engine temp was around 120 on the Smartcraft gauges and would drop to 65 degrees at full throttle. The water temp in the lake is 58 degrees.

A couple of weeks ago it was idling at the ramp on Tablerock and I got a high temp alarm. Shut the engine off and restarted it and the alarm went away. It didn't alarm the rest of the day and I idled out of a couple of creeks longer than what I did at the ramp. Again though, I would have to give it some throttle to stop it from dieing.

The only other thing I can say is when I put it back into neutral when it wants to die it will recover, and run at 1600 rpms and I would have to snap the throttle to get it to idle down.

New fuel filter, fresh gas, good oil, new spark plugs.

What am I missing?

[JOE54]

whats fuel psi doing when "loading up slowly " , ?????

[EuropeanAM]

1. Make sure water pump is fresh- it's an ANNUAL replacement item.

2. Verify BOTH banks of cylinders are coming up to temperature properly. A cold cylinder bank (sticking thermostat) can cause this.

3. Check fuel pressure and monitor it when the engine starts running rich and "chokes out". Video if possible (have someone assist you).

4. Check pulse pump diaphragms (better yet, just rebuild it).

[FeFanatic]

1. Make sure water pump is fresh- it's an ANNUAL replacement item.

2. Verify BOTH banks of cylinders are coming up to temperature properly. A cold cylinder bank (sticking thermostat) can cause this.

3. Check fuel pressure and monitor it when the engine starts running rich and "chokes out". Video if possible (have someone assist you).

4. Check pulse pump diaphragms (better yet, just rebuild it).

I can video later this week. Lower unit is new as of last Wednesday. It has a new water pump on it. I will check the thermostats, it has been on my mind. Pulse pump was rebuilt two years ago during powerhead (mercury reman) replacement.

FWIW, I did have to adjust throttle plate to .020 as it was worn down to .004. I thought that would correct the issue and it did help some.

[FeFanatic]

OK, so I had a tournament this weekend so I tried to resolve this on a Friday. I brought a fuel pressure gauge and I have a DDT. So, I ran the engine for about 15 minutes at wide open throttle and went back to the ramp. There I let it idle in gear to the ramp and it was stumbling bad. So, I pulled the cowl and ran a fuel pressure test. The fuel pressure stayed at 48psi. Engine would stumble and die.

So, I thought I would readdress the throttle plate issue that I had earlier where the throttle plate had no gap at all. I had set it at .020 according to the manual. While idling in gear I adjusted the throttle plate back to closed and it actually ran better but it still chugs and hunts to idle.

I checked the spark plugs firing with the DDT and if correct I have four dead cylinders. Again, I couldn't get much of a rpm difference when running the test.

So, after that I was at a loss and decided to limp it through the tournament. As far as idling in gear went it wouldn't load up and die like before but it was not idling smoothly.

This thing as a great hole shot when jumped on. At low rpms it has a intermittent missing issue. At 1200 rpms in gear and pushing water it runs smoothly. Push it to 1700 rpms and it's smooth for a few seconds and then one cylinder goes dead. It's a definite miss. Push it a little further and the cylinder picks up again and seems to be better. You can feel the cylinder stary working again. I can't tell you which it is though.

So, if I were working on a truck or car engine I would be looking for a bad mass air sensor or a vacuum leak.

The history on this as far as I can tell is the powerhead was replaced in 2015 with a Mercury remanufactured unit. So, now I am wondering if this may have been an issue since the beginning. The fact that the throttle plate was totally closed makes me think it was.

The engine has to be getting air from someplace else than the throttle plate to be running. I can't see any gasket damage from looking but I am thinking of pulling the front of the engine and reed plate to see.

Would that make sense?

I'm t hinking with a vacuum leak as it was with the throttle plate set at .020 my rich condition was due to the computer trying to keep the engine idling and was enriching the fuel to do so.

Any help appreciated.

[EuropeanAM]

So, I pulled the cowl and ran a fuel pressure test. The fuel pressure stayed at 48psi. Engine would stumble and die.

THIS is your problem. Fuel pressure is high, likely either a plugged screen for the regulator, or a failing regulator.

[FeFanatic]

I will check it. I thought I read that 48psi was within spec.

[JOE54]

41-45 PSI

[FeFanatic]

Just an update. I pulled the filter and it is clean. So, I removed the regulator and noticed that the vacuum hose to it was snug but not tight. It did have witness marks from a zip tie but none was there. I have a vacuum pump and hooked it to the regulator and ran a fuel pump test with the ddt. With no vacuum it reads 48 psi. I put full vacuum to it and got 40-41 psi. So I played with different vacuum settings and could get in the range at 5" vacuum. So, I checked the vacuum line back to the intake plenum and it looks like it's good. It will be a couple of days before I can go further but I plan to take it, put muffs on it, start it and see if the vacuum line has vacuum. If not then I will chase that issue. I re-looked in the book and found it was 41-45 psi and I can't for the life of me figure out why I thought 48 was OK. It must be altimers. It's hell getting old.

Will update with what I find.

[lpugh]

You will surprised how little vacuum it has at idle. Don't let it confuse you, the is not a four-stroke street motor, think really big cam drag race motor.

[FeFanatic]

Well, I hope it should have at least 5".

[lpugh]

maybe, 4 to 6 as I recall, its been several years since I actually checked one. At 1500 rpm it come quite a bit. with scan tools I just watch the map reading

[FeFanatic]

My concern is that there isn't enough vacuum to operate the regulator. That coupled with the fact that it runs better with throttle plate totally shut off brings me back to a leak somewhere. It will be a day or two before I really know.

[lpugh]

My concern is that there isn't enough vacuum to operate the regulator. That coupled with the fact that it runs better with throttle plate totally shut off brings me back to a leak somewhere. It will be a day or two before I really know.

Computer programing compensates for that, Doubt that is your problem.
Verify gauge accuracy first. Follow Don and Joes steps to isolate it

[FeFanatic]

OK, so. I can get the fuel pressure to 45 psi at idle. Vacuum is between .5 to .7" of vacuum. Adding a tie wrap to the vacuum line helped the high pressure issue. But that didn't seem to help very much if any. While running and when reved up to around 1200 rpms the fuel pressure drops to around 43 psi. The cylinder balance test doesn't seem to be prominent. It's hard to tell on most all cylinders any drop in rpms when I run the test. That being said I could disconnect up to 3 cylinders on each bank, reconnect the spark plug wires and tell that the cylinders are firing. Compression test is right at 120 on all cylinders with 118 lowest and 121 highest. Again, while running a fuel pressure test it will drop to 40 psi when pump stops and stays there for about 10 minutes then slowly drops to 30 and will set there for a good 30 minutes.

Someone mentioned think big cammed race engine. That's how this motor is jumping around. Just like a big cammed race engine. Runs great at mid and full throttle. Just doesn't want to idle in gear under any load.

[JOE54]

any idea what reeds look like in this engine ????? hmmmm i may have to send you my test regulator ,

[FeFanatic]

I have no idea on reed condition. I don't believe the motor has more than 150 hours on the new Merc reman. FWIW, the only other thing I had some concern with is the TPS as it will go to around .150 at idle and is kind of erratic. Even if I manually take it back to .190 while idling it doesn't make a difference in rpms or misfiring. I kid of ruled it out since there wasn't any change. Now, if I got it up to .25 or more it would increase idle speed but not stop the erratic running.

[EuropeanAM]

Look carefully at plugs: Make sure you're running Champion QL77CC (only).

Reed inspection is in order. Even one chipped reed will make for a very rich running engine (remember, the MAP sensor is also connected to Manifold Pressure).

[FeFanatic]

It has the correct plugs. Map was at 12.8 running and a little over 14 key on and engine off.

[EuropeanAM]

How steady is the MAP at idle? Varying by how much (highest and lowest reading over a 30 second period, for instance)?