Engine Idiling rough

jbauman102

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Sep 19, 2011
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I have a 2004 Volvo penta 5.7 gxi-e and it idles very rough, you can even smell gas when idiling. The injectors have been rebuilt, new iac, tps, new cap, plugs and wires, had new heads put on do to crack. I had 2 different mechanics look at it and h ook computers to it and they can't figure it out. One suggested the computer could be stuck in maintenance mode. Any suggestions.
 

bajaunderground

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Apr 18, 2008
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There are a lot of possibilities...

If it is hooked to computer and there are NO error codes flashing, then it's most likely a mechanical problem.

If you replaced heads, I'd start with making sure your lifters are all torqued properly? That motor should have roller-rockers.

Check for vacuum leaks around the intake. Could also be water intrusion in your intake manifold...if the heads had cracks due to poor or non-existent winterization, then that's another avenue to trouble shoot...risers as well. Did you check all the parts you didn't replace to make sure they were crack free?

Scott Danforth and others will be along to help troubleshoot...I am by no means an expert, only an garage mechanic, at best.

Good Luck with you issue.
 

jbauman102

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I live in central Florida so never winterized it. As far as the torqing I would hope my mechanic did it right but I will check on the things you listed. Thanks
 

alldodge

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Check vacuum by pulling the hose off the manifold going to the PCV valve. The vacuum should be smooth and steady, but being its running rough it probably won't be. Let us know what the reading is.

Does the motor run fine other then the rough idle?
Has a compression test been done, and if so what were the readings?
 

jbauman102

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It runs fine when not in idle and want I open the throttle a little, I will check on the compression
 

Darrenmb

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I have a 2004 Volvo penta 5.7 gxi-e and it idles very rough, you can even smell gas when idiling. The injectors have been rebuilt, new iac, tps, new cap, plugs and wires, had new heads put on do to crack. I had 2 different mechanics look at it and h ook computers to it and they can't figure it out. One suggested the computer could be stuck in maintenance mode. Any suggestions.

When you say hooking computer to it, and they think its in maintenence mode, you are leading me to believe its just a code scanner, find someone that can actually tie in and read the sensors and.voltages! There should.be no "thinking" its in maintenence mode. Also as.mentioned above, check rockers and for vac leaks..
Good luck!
 

Scott Danforth

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if they plugged in with a good diagnostic tool such as Rinda or similar, they should be able to see what every sensor is doing and what the ECM is doing.

As AllDodge indicated
compression reading will tell you the condition of rings, valves, etc.
the vacuum reading will tell you if you have a vacuum leak, bad lifter, etc
a fuel pressure reading will let you know the condition of the fuel cell and regulator as well as indicate if you have a hanging fuel injector

make sure the plugs are correct for the motor (long reach such as NGK TR55). a short reach plug would result in incomplete burn at idle
 

Dave-R

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Mar 18, 2008
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If the vacuum readings, and compression check out, and there are no vacuum leaks. I would look at your Manifold air pressure sensor. Especially when the engine is running very rich, and has a shaky idle. This was the fix for my 2011 5.7 GSI . I had replaced virtually everything else before this. My engine did not throw a code for this, but on the Rinda Diacom the manifold atmospheric pressure, and vacuum pressure were not reading in parameters. My engine was also running very rich, and I could also smell gas. It had been at a repair shop for 3 months and the tech was unable to identify the problem. When I brought the boat home, I thought I would replace the M.A.P. sensor, as that was the only other electronic sensor that was not replaced. Bingo she purrs like a kitty. The Rinda I bought had a very good troubleshooting section that really helped me. The tech even thought I had mechanical issues with the engine, as I just had it rebuilt. I hope you find out the cause and post it. Good luck Dave-R
 

jbauman102

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Sep 19, 2011
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The compression was good on all cylinders 180 to 200, vacuum and fuel pressure was also good. I forgot to mention it kicks back when trying to start. Where is the MAP sensor locared. Im working with a mechanic who is doing all of this and I was right there with him. He called a buddy and they mentioned some kind of sensor under the front pulyl that sends info to the distributor or another sensor on the distributor.
 

alldodge

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The MAP is item 4 in link below, it is located on the intake
https://www.marinepartseurope.com/en...-25-22171.aspx

There are two position sensors, one on the distributor and one on the timing chain cover. The one on the timing cover is the crankshaft position. If there is no cable connected to the side of the distributor then that sensor is not used. If the motor is running fine other then idle then I don't see it being the position sensors

With it kicking back, then this could also be a timing issue.
 

Senior B

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Is there any evidence of water intrusion on the plugs? My last boat was ingesting water from a defective intake manifold gasket and had very similar symptoms. Rough idle, tuff to start some times from hydro lock but ran fine once it got going. Didn't impact power or top end. Never had water in the oil but it could have been cooking it off too as the lifter valleys looked a little milky when I fixed it. Second the call on a possible MAP sensor or its connections.
 

QBhoy

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Simple start would be to pull the plugs out and have a look. Any sign of water, may mean you'll have to look towards the risers/manifolds for leakage. That'll make her run rough at idle. Just an easy check to rule it out.
 

jbauman102

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Sep 19, 2011
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So my buddy has the exact same engine in his boat and we swapped out the map sensor and the computer and that didn't solve the problem. The plugs look fine no water intrusion. We are thinking it some kind of timing issue since it kicking back so much when trying to start it.
 

jbauman102

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Sep 19, 2011
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Finally got it running right, when they rebuilt the upper half they didn't put the distributor in right, it was one tooth off.
 
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