5.7Gi-A idles at 600 rpm, then rises to 2000 to 2500 rpm on it's own

[gverb1219]

So I have a 2003 VP 5.7L Gi-A. The engine starts and runs fine while cruising. But after slowing and trolling for about an hour the idle will start getting rough like it is "loading up", then all on it's own the engine rpm will rise to 2,000 - 2,500 rpms for about 5 seconds, then idle back down.....idle real rough.....then rise back up, then down, then up......this will go on until I actually manually raise the throttle with the controller to about 2,000 rpm and hold it for a minute. Then when I pull back it will idle nicely at 600 rpm...........for about 1/2 hour.......then the process starts all over again.
I have changed the fuel filter 3 times in the past 3 months....they always look fine and no sign of water or dirt.
I have pulled the injectors and had them serviced.....they have and still do spray completely normal...no drips
New rotor, cap, plugs, wires...3 months ago
Engine was always cooled with coolant, (closed system) until about 4 months ago when heat exchanger went bad, but problem was happening before I switched to raw water cooling.
It will run fine at cruising speeds for long period with just an occasional slight loss of rpm...but hardly noticeable.
I am running out of ideas........any help would be appreciated.

PS: I do not have any fuel pressure gauges or any "specialty" tools

Gary

 

[alldodge]

So I have a 2003 VP 5.7L Gi-A. The engine starts and runs fine while cruising. But after slowing and trolling for about an hour the idle will start getting rough like it is "loading up", then all on it's own the engine rpm will rise to 2,000 - 2,500 rpms for about 5 seconds, then idle back down.....idle real rough.....then rise back up, then down, then up......this will go on until I actually manually raise the throttle with the controller to about 2,000 rpm and hold it for a minute. Then when I pull back it will idle nicely at 600 rpm...........for about 1/2 hour.......then the process starts all over again.
I have changed the fuel filter 3 times in the past 3 months....they always look fine and no sign of water or dirt.
I have pulled the injectors and had them serviced.....they have and still do spray completely normal...no drips
New rotor, cap, plugs, wires...3 months ago
Engine was always cooled with coolant, (closed system) until about 4 months ago when heat exchanger went bad, but problem was happening before I switched to raw water cooling.
It will run fine at cruising speeds for long period with just an occasional slight loss of rpm...but hardly noticeable.
I am running out of ideas........any help would be appreciated.

PS: I do not have any fuel pressure gauges or any "specialty" tools

Gary

I'm thinking a bad connection or the IAC may have an issue. Now the IAC or MAP could cause what your seeing at low idle but loss of rpm at high could be MAP or fuel pressure regulator.

What is the temperature running at idle and higher rpm?

 

[gverb1219]

I'm thinking a bad connection or the IAC may have an issue. Now the IAC or MAP could cause what your seeing at low idle but loss of rpm at high could be MAP or fuel pressure regulator.

What is the temperature running at idle and higher rpm?

Normal running temp is just around 170 or so..............doesn't change more than a couple degrees either way.
It mostly always happens during times of long trolling periods. During the first start up of the day it runs fine at idle speed (600 rpm) for about 45 minutes to an hour. Then it starts acting up. It always sounds like it is going to stall.....idles down to about 300 or 400 rpm.......like it is starving for fuel or loading up. I know....two different problems. But when it starts running rough it sounds like the throttle body is "sucking air" real hard. If I put it in neutral and try to rev it up.....sometimes it will "pop" backfire a bit before reving up.....then it clears up and is ok for about 20 to 30 minutes. It will randomly throttle up to 2,000 - 2,500 rpm for no apparent reason whether it's idling in gear or not. For the most part it runs pretty good at high rpm's..very little notice of the rpm issue..and thats only if I throttle up right after it's been acting up. If I go right out and run at cruising from the start it's ok ......until I slow to idle for a long period.
Next time I'm out I will try to get it on video.......

 

[alldodge]

Normal running temp is just around 170 or so..............doesn't change more than a couple degrees either way.
It mostly always happens during times of long trolling periods. During the first start up of the day it runs fine at idle speed (600 rpm) for about 45 minutes to an hour. Then it starts acting up. It always sounds like it is going to stall.....idles down to about 300 or 400 rpm.......like it is starving for fuel or loading up. I know....two different problems. But when it starts running rough it sounds like the throttle body is "sucking air" real hard. If I put it in neutral and try to rev it up.....sometimes it will "pop" backfire a bit before reving up.....then it clears up and is ok for about 20 to 30 minutes. It will randomly throttle up to 2,000 - 2,500 rpm for no apparent reason whether it's idling in gear or not. For the most part it runs pretty good at high rpm's..very little notice of the rpm issue..and thats only if I throttle up right after it's been acting up. If I go right out and run at cruising from the start it's ok ......until I slow to idle for a long period.
Next time I'm out I will try to get it on video.......

I take it this is an EFI engine and with that I would suggest removing the IAC (Idle Air Control) valve and clean it. Then reinstall and see if that helps

 

[gverb1219]

I mistakenly said it was a 2003.......the engine is a 2002 5.7 Gi-A TBI engine. I will check the IAC today and see if that helps. I am wondering also if it could be the fuel pump going bad.....?

 

[alldodge]

It may have something to do with fuel pressure, but a pump doesn't get weak one time and then come back after revving the engine up for a while. When a pump starts going it stays that way or gets worst. Now if there is a vacuum leak on the fuel pressure regulator, that would be in the maybe, but then again a vacuum leak doesn't go and come

 

[gverb1219]

I pulled the IAC valve off and cleaned it up. It didn't look that bad.....just pretty "sooty". I put it back on and started the engine to let it run, but then the rains came.......so I'll have to wait till tomorrow afternoon to really let the engine run for an hour or so. I'll let you know what happens. Thanks for the info so far..........

 

[4now04]

I had very similar symptoms on my '02 Volvo 5.7Gi-B last fall. It turned out to be a bad fuel cell (fuel pump assembly mounted on the right front corner of the engine). The fuel cell includes a high pressure pump, a low pressure pump, fuel filter, and water cooling from the engine's water cooling system. Do some research and you will probably find that it is a somewhat common problem. You can get a fuel pressure tester gage for around $50. Fuel pressure specs should be available on line. A new fuel cell assembly is around $600 on ebay, or maybe $900 at your dealer. Labor is in addition to that, as I found out last fall. If you have access to a marine code reader you might be able to simplify your troubleshooting. It would be a good idea to eliminate other possibilities before having to change the fuel pump, but I wouldn't be surprised the pump is bad. From my research, I did not find anyone that repaired the fuel cell assembly. There are a couple Youtube videos on troubleshooting and changing this fuel cell, if that helps. Best of luck.

 

[Fun Times]

If cleaning the IAC and hopefully the inside sides of the throttle body and both throttle plates??? doesn't seem to help, then one suggestion would be you "may" have an ignition module getting hot and cycling the ignition timing. Make sure the distributor hold down bolt is thigh and the area is corrosion and excessive paint free to allow a good body ground.

Check all power and ground wires and cables for tight clean connections.

Using a multimeter, check your 12 volt power at the alternator area while the idle is surging also carefully check for excessive heat while your at it.

If you can get your hands on a timing light, connect it to the high tension plug wire between the coil and distributor cap and make sure your light has a consistent flash before and during the surging. This may not help much but you could try watching the ignition timing connected to cylinder # 1 during the surge just to know what it's doing as far as advancing goes. But do not reset timing as there is a special procedure needed to stabilize the timing.

Check ignition coil for excessive heat just in case.

Sometimes in situations such as this the IAC is compensating extra air for another problem should it want to die...Which could be the timing is moving, or the ECM thinks the throttle position sensor has moved for examples. Be sure the throttle plates are fully closed "by hand" once the surge starts acting up. If it's open just a bit, you could get a surge like that. Hence the inside throttle body and throttle plates need to be clean.

A marine scan tool say from Rinda Technologies is normally best to help find issues such as these.

What did the spark plugs look like? Fuel fouled at all?

Testing the fuel pressure on a TBI engine is a bit more challenging to do vs an MPI engine model as there is no fuel schrader valve to easily connect to. Need to connect right at the throttle body. This should do it. http://www.autozone.com/test-scan-a...ctron-gm-tbi-fuel-pressure-tester/232719_0_0/

Normally I'm not one to say through parts at it, but if you come to believe there is a timing jump issue causing this then the cheapest way I could tell you for testing this theory is to try a new ignition module found under the distributor cap. Here's the thing, if you buy one from a marine dealer/Volvo/Merc etc., you are looking at around $165.00ish. But if you do some shopping either online or calling auto parts stores in your area, you should be able to find one at a lower cost. You'll want to use AC-Delco part number D1965A as it is the same module found on your engine model which is Volvo part number 3854003.

You can find the AC-Delco part on ebay new (or used so be careful) in the $40.00 range. And to be honest these parts do have a tendency to fail in numerous ways without much warning. So it's really a good idea to have one onboard with you should you encounter a no spark situation one day out of/in the blue.

If you try/buy a new module, you'll also need to buy Heat Transfer Compound such as Mercruiser part number 92-805701 for the bottom side of the module.

http://www.michiganmotorz.com/mercruiser-quicksilver-compoundheat-p-857.html

http://www.ebay.com/sch/i.html?_fro....TRC0.H0.TRS0&_nkw=D1965A&ghostText=&_sacat=0

For heat testing purposes , an infrared temperature gun is a good idea to have as well. http://www.autozone.com/test-scan-a...rared-thermometer/951642/?_requestid=14124265

Hope you find something simple, keep us updated and good luck.

 

[gverb1219]

....still waiting for better ocean conditions to check it. Going out this weekend will report back what I found.....