5.7 L EFI RPM idles high intermittently

[blieber]

I just bought a 1998 Sea Ray 230 BR with the 5.7 L EFI, Bravo 3. I noticed that it intermittently will idle at 1200 RPMs. This occurs AFTER I have started and driven the boat. The only way to "fix" the high idle is to turn off the motor and restart it. Then it idles at 600 RPMs. If I drive it again, it may or may not again idle at 1200 RPMs when I place it back into neutral. Again, it "fixes itself" when I turn the motor off and restart.

I searched the forum and found a post from two years ago by someone with the same issue. I tried PM'g him and haven't heard anything. He did a lot of work trying to fix the issue and the thread ended without a resolution.

I will paste his post below:

"5.7 EFI High Idle

Don or anyone - hoping can help?.

1998 EFI Serial Number 0L025442

Developed high idle issue last couple of years. Doesn?t happen every time. Worked on it last summer - got boat out of storage this spring - put in a new TPS and still happening.

Symptoms: Start engine ? idles normal (600 RPM). After 20-30 minutes of use ? shift to neutral and idles high (1200 RPM). Now interesting part ? simply shut off and re-start and it idles normal.

It?s the fact that shutting off and restarting ?solves? the problem that is causing the real head-scratching.

I have worked with a Merc mechanic on it.

We hooked up to scan tool. No error codes. Only unusual reading is the Throttle Position reading ? sometimes at 0% but sometimes at 2%. (Normal range according to Merc is 0%-1%).

In full disclosure: The only other issue is the Tachometer on the boat sometimes is not working or running backwards. If I understand correctly the tachometer and shift interrupter switch are on the same circuit.

Actions:

1. Cleaned throttle body
2. Adjusted the cables even though seemed fine to begin with ? now really solid pressure pushing the throttle plates closed (Throttle Position still reads 2% on scan tool sometimes)
3. Replaced IAC
4. Replaced TPS (Throttle Position still reads 2% on scan tool sometimes)
5. Replaced PVC value
6. We hooked up a temporary bypass for the shift interrupter switch.

We bypassed the boat?s electric panel by hooking up a separate portable control panel (key switch, tachometer, etc.) We couldn?t get the problem to occur at that point but it wasn?t clear that we ?solved? the problem versus the problem just didn?t occur right then.

The Merc mechanic is hoping to get in touch with a specific ?older? Merc Regional Field representative who is familiar with the older MEFI I systems. He talked to a younger guy in Fond du Lac but didn?t seem as up on the older EFI system.

Merc mechanic thinking of replacing plugs and/or spark plug cables and check compression. His thought is that maybe the ECM is able to correct for bad plug but it shows up at idle. Alternatively, he thinks the ECM is going bad ? but I would think we would see lots of other issues if this was the case. He admits that is unlikely the problem but simply running out of ideas.

Any ideas?
Any suggested diagnostic process?

Makes for alot of fun docking - when idling too fast and can't shift into neutral/reverse. "


So, does anyone have any ideas on what this might be or how to best approach it?

Thanks,
Bill

 

[alldodge]

Have you tired grabbing a hold of the throttle body butter fly and see if you can slow it down by applying pressure?

 

[blieber]

I have not. I will try. I am not a mechanic by any means, but would like to get an idea of what the most reasonable approach to this would be (obviously I will have a mechanic check it out, but I like to be armed with a bit of knowledge so that I understand the problem to the best of my ability before talking to the mechanic). Or the most likely cause. If that does slow it down, what does that tell me?

 

[Bondo]

If that does slow it down, what does that tell me?

Ayuh,.... Welcome Aboard,.... It tells ya the throttle cable needs adjustin',....

At Idle, the cable should be holdin' a slight bit of tension against the idle stop screw,...

 

[alldodge]

If you can push and it slows down then its as Bondo mentioned, or could be the throttle body is binding

 

[blieber]

Thanks for the picture! I am able to apply very mild pressure in the direction you show in the picture. This does bring the RPMs down to 600. However, the issue only happens sporadically. I lubricated all the moving parts on the throttle body (if that is what you call the arms that the cable attaches to in the picture above). It doesn't seem to be binding. I don't feel any substantial play in the cable. I move it maybe a few millimeters forward and it brings the RPMs to 600.

The funny thing is, if I just throttle only (by pushing the button in on the base of the throttle so that it doesn't go into gear), and rev up, it always settles back down to 600-800 RPM, as it should. The problem only occurs if I shift into gear. I know it is going to occur when I slow down and notice that the RPMs only go down to 1000 (never below 1000) and shift into neutral. As soon as I hit neutral, it revs to 1200 RPMs. If I slow down and the RPMS go below 1000, then it behaves normal when I shift into neutral. It's like it gets stuck at 1000 RPMs and won't go below, no matter how slowly I slow down. I even give it plenty of time with the boat barely in gear and it sporadically won't come down below 1000 (even though the normal RPMs when shifted just into forward is 800). Then I shift into neutral and, bam, back up to 1200 RPMs. And it's not always 1200 RPMs. Sometimes it is 1400, sometimes 1100, but generally is 1200.

If it is the cable needing adjustment, would this happen sporadically as I describe? And why would turning the engine off and back on fix the problem?

Thanks,
Bill

 

[alldodge]

If it is the cable needing adjustment, would this happen sporadically as I describe? And why would turning the engine off and back on fix the problem?

A car has a spring to pull the throttle plate closed when the pedal is released, a boat does not. The cable on the boat needs to push it closed. This is the reason that if there is a bit of slop, even a couple mm can cause the issue. Turning the motor off stops air from being drawn through the throttle plate, This allows the plate to completely close

There is a barrel adjustment which may need one or two turns. It will either be held in place by a cotter pin or nut and washer. With motor OFF and shifter in neutral, remove the barrel. Now turn the barrel so that when it is reinstalled, there is a slight pressure pushing the throttle closed.

 

[blieber]

Thanks guys. I adjusted the cable as AllDodge suggested and it seems to be working fine!!!!! Thanks everyone for the input. I am no mechanic by any means and this saved me. Special thanks to AllDodge for the picture and the explanation. I thought there was a spring!

Hopefully this is the last I will have to post on this particular thread!