volvo throttle position sensor

[marineteam]

I have twin 1995 volvo (Ford) 5.0 FI engines that have run perfectly since new and always started immediatly when the ignition was turned on and have run perfectly until turned off. Both engines have approximately 300 hours of use since new. One of the engines began to die at idle and then would run very sluggish when restarted. I finally found a mechanic that diagnosed the problem as a faulty throttle position sensor. It was replaced and the engine would start and idle but still ran very sluggish. I had the engine reinspected and found gas in the crankcase and carbon buildup on the plugs and valves. Could a faulty throttle position sensor cause gas to be forced into the crankcase? The engine had good compression and has never shown any problems before. Can a throttle position sensor go bad immediatley or
do they go bad over time? When a throttle position sensor is replaced are there any other things that should be checked or replaced at the same time? As mentioned there was no warning prior to the engine beginning to kill at idle.
Thanks for your help

 

[marineteam]

Re: volvo throttle position sensor

Does anyone have any ideas, solutions or suggestions. I could sure use some information.
Thanks.

 

[lilmandavis]

Re: volvo throttle position sensor

Im not to sure what setup you have on your boat. but as a avid auto mech, I would recomend replacing the tps and the iac valve at the same time... With OEM factory parts only on that.

 

[whywhyzed]

Re: volvo throttle position sensor

Can a throttle position sensor go bad immediatley or do they go bad over time?

over time, but the problems tend to show up suddenly in one position where it spends a lot of time- like idle

When a throttle position sensor is replaced are there any other things that should be checked or replaced at the same time?

not really... but the problem does sound like the IAC
That's the thing with everything electronic...and electonically controlled... it quits eventually

some IAC info:
http://www.p71interceptor.com/repairs/iac/

I sure like carburetors on boats.

 

[marineteam]

Re: volvo throttle position sensor

Thanks, I appreciate the information. I will look at both suggestions and hopefully better understand what has happened.

 

[SuperNova]

Re: volvo throttle position sensor

IAC problems will give you a sloppy idle, but usually not a sluggsh engine or carbon buildup. Most likely you have a bad MAP sensor/vacuum/circuit or a leaky injector. If the carbon is isolated to one or two cylinders I would look at the injectors-just allow the system to pressurize and then pull the rail assembly. If any injectors are leaking you will see them drip.
If the carbon is on all the cylinders, then I would lean towards the Map sensor system fault or fuel pressure regulator.
--
Stan

 

[marineteam]

Re: volvo throttle position sensor

Thank you for the information. All of the replies I received have been very helpfull and informative. I appreciate the time you have taken to provide the info.
Thanks