5.7L Mercruiser dies on idle

[kurbla]

Hi guys, I have a question and need some help. I have a 1998 Searay 210 Sundeck with a 5.7L TBI Mercruiser #0L082188. When I first start it, runs great. Once it warms up to about 140 it will load up slowly and die. It then starts right back up and will load up and die again. If I give it some throttle it wont typically do it again until I shut it off and start it again. If I unplug the temp sensor and force the computer to use default values it runs fine on idle. I have replaced the Map, tps, idle control solinoid and temp sensor, still have the same issue. When on the lake it is intermittent. In addition to this problem when I was chasing a backfiring issue, I replaced the plugs, cap, rotor, coil, dist pick up coil and fuel pump. Found out the shift interrupt switch had shorted out. fun fun. Any ideas on the idle? It is not setting any trouble codes.

Thanks

 

[tommays]

Re: 5.7L Mercruiser dies on idle

i would go with a service manual for your serial number


It will have flow charts on how to test VS replace and hope for the best


In general you would need to be able to test fuel pressure(really important) and without having a Merc scan tool you are somewhat limited as to what is going on


Tommays

 

[kurbla]

Re: 5.7L Mercruiser dies on idle

Thanks, I have a pressure gauge hooked up to the fuel line. Looks good. 28-30lbs. I do have the manual. It is very helpful. I have a code reader but not the scan tool. May have to take it in. Thanks again.

 

[kurbla]

Re: 5.7L Mercruiser dies on idle

Updated info. The engine does the same thing after I unhook the temp sensor if I let it idle for a few minutes.

 

[Redneck Yacht Club]

Re: 5.7L Mercruiser dies on idle

Need some history on the boat to make a better idea of the problem.
After temp 140 is giving some kind of clue.
Need info.....
Max temp?
Max rpms?
Is the tach. doing anything werid?
You said ya replaced the MAP sensor and the IAC valve. Ya need a DDT or a CDS to find out if the ranges are right.Alarms will go off if shorted or open.
And watch the injector spary at idle, see if it driping or spary looks werid.
Some of these searay also had heat related issues with fuel, like vapor locking. Is the fuel a winter blend?
And unhooking the temp. sensor is taking one the inputs away from the computer to run the engine propely.

 

[kurbla]

Re: 5.7L Mercruiser dies on idle

Thanks for the input. The boat normally runs about 170 degrees. WOT 4700. Runs great through the whole range but idle. TP sensor shows .5v at idle 4.5 wot. Changed the ECT sensor due to a 14 trouble code being set now and then. The injectors don't seem to be dripping. I am still a little leary of them because the boat had set about 18 months and had not been run. Tach drops down to about 625 rpm from 650 and then it seems to load up and die. It will start right back up and then load up and die again. Today when I was messing with it, it ran fine for about 20 min. Temps came up to 170, idle was great. turned it off and then started it again and it loaded up and died. Restarted and the idle was fine. not setting any codes. I have run about 100 gal of fuel through it in the last month. I did put mercury"s fuel conditioner-cleaner in the last batch. Injectors do have a patchy spray at idle but have a nice cone shape at about 1000 rpm. Don't know if that is normal or not. I only have a code reader not a scan tool so I can't tell if I am getting an in range failure on one of the sensors. The crazy thing is it does not do it all the time. If I have been running around the lake and then stop and idle, it usually idles fine. It only seems to do it when it is a pain in the butt. Loading and unloading at the dock etc.

 

[Redneck Yacht Club]

Re: 5.7L Mercruiser dies on idle

Ya, not having a scan tool is tuff to fiqure that one out.
Is your voltage droping when it starts loading up?
Ya need to find out the MAP sensor range too.It will not set a code if its out of range, only if its open or shorted.
Check the fuse at the starter, it will be 90amp fuse, if ya can turn the stud, its screwed up.Heat dose affect these fuses sometimes.
When it starts loading up, dose the fuel cone change? Like small drips?Your Sensor in the distrubler controls open and closing of the injectors. That also might be a problem and they too breakdown due to heat problems.
Also, try letting run at idle without the aircleaner on. See if anything changes.

 

[kurbla]

Re: 5.7L Mercruiser dies on idle

I'll check it out. Thanks