Mercruiser Bravo 5.7 liter stalls when coming down to idle off of engine rev.

[Mike4130]

Greetings to all, I just bought a 2000 Sea Ray 290 Sundancer and am running into an issue with one of my engines. My Starboard engine often stalls when I take the RPMs down to idle from a higher rev. At that point when I try to restart, I have to open the throttle half way to get the engine to restart. To try and resolve this, I have recently done the following, Plugs, Rotor, Cap & Plug wires. The issue is still present. Any help or thoughts with this matter will be greatly appreciated.

 

[tpenfield]

:welcome:

. . . to iBoats.

If these are carburetor engines . . .

Will the starboard engine idle normally with the throttle fully in the idle position? (or do you have to keep the throttle up a bit?) Is there an RPM difference in the lowest idle speed (per the throttles) between the engines?

Just thinking the low idle stop setting on the carburetor may not be set quite high enough . . .

If these are EFI engines, then a different set of issues. Probably will need to check for fault codes, etc.

 

[jrs_diesel]

We need a bit more information to help you out. We know you have a 5.7, and that's it.

Can you post your engine serial number (should be on the sticker on top of the flame arrester)? Also, is your engine carbureted, or fuel injected? What is your idle speed at currently, or does it idle at all? When you say higher revs, do you mean revving in neutral or in gear?

 

[Mike4130]

Sorry, here's a little more information. Engine serial numbers - OL638458. These are throttle body injected motors. Engine will idle fine but when I give it some gas in neutral then bring back to idle most times it will stall. At that point, I have to open the throttle to about halfway to get the engine to restart.

 

[alldodge]

Howdy

Does the motor idle smooth so long as the rpms are not increased, no matter how long?
Once it restarts with throttle open, will it continue to idle when throttle is brought back to neutral, or keep dying?
When cold, does the motor start right up or does it take some more throttle?

 

[Mike4130]

The motor idles smooth once its running. And when I bring the throttle back to idle, sometimes it will stall, sometimes it will stay at idle. Whether its warm or cold I have to give it half throttle to start.

 

[alldodge]

Starting to sound like your IAC (item 7) may be sticking. Suggest removing it and clean it with throttle body cleaner or such, and do not use anything with MEK. Note the IAC should move in/out freely. The O-ring (item 9) should be replaced but may get away with reusing so long as it looks good.

Look down the bore of the throttle body and look for a piece of foam rubber, might not be there. If you find it this is the IAC muffler. Remove and clean (needle nose pliers) with soap and water then reinstall.

http://www.mercruiserparts.com/bam/subassembly/31886/4856/130

 

[alldodge]

Would also be a good idea to check fuel pressure. Should be 43 psi at 1800 rpm
To check pressure you would need a fitting like this one to place inline at the TB part number 91-806901

 

[alldodge]

Would also be a good idea to check fuel pressure. Should be 43 psi at 1800 rpm
To check pressure you would need a fitting like this one to place inline at the TB part number 91-806901

 

[Mike4130]

Awesome. This gives me something to start with. I'll give this a shot and respond with any progress. Thanks again everyone!

 

[Mike4130]

AllDodge I'm thinking about just ordering a new IAC. I found one on Amazon for $65.00. What are your thoughts on aftermarket parts such as this?

https://www.amazon.com/Control-Merc...rd_wg=tpDfh&psc=1&refRID=RC49C7JTWSSP83611YY1

 

[alldodge]

You could do that, but I would try cleaning it before replacing

And auto or marine its the same item

 

[Mike4130]

Ok, I just try to stay with OEM parts if possible.Thanks again for your help.

 

[alldodge]

Ok, I just try to stay with OEM parts if possible.Thanks again for your help.

The item in the Amazon link is not a Merc part, it says its replaces the Merc and VP part, doesn't say OEM, Mercury, Quick Silver or VP. Its either a GM auto part or Sierra

 

[tpenfield]

FWIW - the various sensors on my MPI engines have the GM part number markings on them. Mercruiser just gets them from GM and re-packages them.

 

[Mike4130]

Well I solved the problem. I started with cleaning the IAC and took the boat out for a test run. Unfortunately the stalling issue was still present. I had dumped some Sea Foam into the tank and thought I may as well run some of this through it to see if that helped. Both engines were running great and I got about 3 miles from my marina when the Starboard engine just died. No hesitation or anything. So I limped back to dock and took some advice from a my buddy who is a mechanic. We just did a ignition system tune up and replaced everything but the coils, so he suggested I replace those. So I went out the next day bought a coil and the motor fired right up and and, it solved the stalling issue! Super happy at this point. Thanks again to all for your insight to this.