Volvo Penta 5.7 High idle only when warm

[01somta]

I have a 1997 22ft Four Winns with a 5.7L Volvo in it with 300hrs. The boat runs great EXCEPT the idle is too high once warmed up. The boat will idle at around 800rpm when cold and around 1,200 to 1,500rpm once warmed up . Most of the time the idle will stay high no matter how long you set and let it idle, sometimes turning the boat off and back on will correct the high idle. I first though vacumn leak but I would think the idle would be high all the time not just when warm and wouldn't correct itself sometimes once turn off and back on. So could it be the MAP sensor or maybe the idle control valve.

 

[Don S]

Re: Volvo Penta 5.7 High idle only when warm

You may just need a throttle cable adjustment or the cable itself is failing causing the problem.
Disconnect the throttle cable from the carb linkage and see if it idles ok. Does the cable move easily and smoothly? Then adjust the cable end to put a slight preload of pressure on the carb linkage to the idle position.

 

[01somta]

Re: Volvo Penta 5.7 High idle only when warm

You may just need a throttle cable adjustment or the cable itself is failing causing the problem.
Disconnect the throttle cable from the carb linkage and see if it idles ok. Does the cable move easily and smoothly? Then adjust the cable end to put a slight preload of pressure on the carb linkage to the idle position.

It is TBI and the cable does move easily/smoothly. I would think if it was the cable then it would always idle high correct not just after driving it for a bit?

 

[Don S]

Re: Volvo Penta 5.7 High idle only when warm

Maybe you should post the full model number or SN of your engine so we can answer properly.

Trust me, disconnect the cable and see if it idles. It's easy to do and answers a lot of questions.

 

[01somta]

Re: Volvo Penta 5.7 High idle only when warm

Ok I will give it a try this weekend, anything else I could check while I'm there. The boat is at our lake house about 3 hrs away. :redface:

Thanks

 

[01somta]

Re: Volvo Penta 5.7 High idle only when warm

Ok when I take the throttle cable off it idles fine, the throttle lever snaps back into "idle position" just fine. If the throttle cable is hooked up I have to help the lever back into idle position due to the tension on the cable. It seems like the return spring on the throttle lever is to weak to move the throttle cable back into the idle position. So is it the spring, does the cable need some adjustment or something else?

Thanks
Dustin

 

[Aloysius]

Re: Volvo Penta 5.7 High idle only when warm

could be a sticking idle control motor, or defective TPS. May need a digital voltmeter to check TPS voltage, and a manual to tell you what the brain wants to see for idle voltage. A shop with proper equipment can run the stepper IAC motor to check its function.

 

[Don S]

Re: Volvo Penta 5.7 High idle only when warm

could be a sticking idle control motor, or defective TPS. May need a digital voltmeter to check TPS voltage, and a manual to tell you what the brain wants to see for idle voltage.

I think you misunderstood his reply. With the cable off, it works fine. He does not need to start adjusting or replace the IAC or the TPS. Leave them alone.

The problem is in the cable adjustment. The cable end needs to be turned so it will SLIGHTLY preload the linkage to the idle position.
Your cable wearing inside has allowed it extra slop causing the problem.

 

[Aloysius]

Re: Volvo Penta 5.7 High idle only when warm

You're right, Don. I think he posted that while I was leisurely writing mine.

Don's reply is dead nuts correct.

 

[01somta]

Re: Volvo Penta 5.7 High idle only when warm

I think you misunderstood his reply. With the cable off, it works fine. He does not need to start adjusting or replace the IAC or the TPS. Leave them alone.

The problem is in the cable adjustment. The cable end needs to be turned so it will SLIGHTLY preload the linkage to the idle position.
Your cable wearing inside has allowed it extra slop causing the problem.

The only problem is that the cable is already adjusted all the way in, could I unscrew the eyelet on the end of the cable and dremel it off about a 1/4 of an inch so I could get a little more adjustment out of it? The eyelet that screws on to the cable has probably about a 1.5-2" of threads that's why I was thinking a 1/4" wouldn't make any difference.

 

[Don S]

Re: Volvo Penta 5.7 High idle only when warm

You need to adjust the cable end in the control box. If the lock nut is loose, the cable could slowly work it's way out of the adjustment in the control and make it look like you have no adjustment at the engine.

 

[01somta]

Re: Volvo Penta 5.7 High idle only when warm

I'm about 99% sure I know what you mean by "control box", but to make sure are you referring to the hand lever for throttle control to the right of the driver's seat?

 

[01somta]

Re: Volvo Penta 5.7 High idle only when warm

Sorry double post

 

[01somta]

Re: Volvo Penta 5.7 High idle only when warm

You need to adjust the cable end in the control box. If the lock nut is loose, the cable could slowly work it's way out of the adjustment in the control and make it look like you have no adjustment at the engine.

After looking at the control box it looks like I have two throttle cables one that is for part throttle and the other for full throttle. I pretty sure that I need to adjust the one for part throttle, but I'm not quite sure how to do that. I can take the cable off of the throttle box but the rod on the end of the cable doesn't screw in or out. The cable looks like it has a rod with an eyelet on the end but if you try to screw that it feels like it just rotates the cable also. I guess what I'm asking is how do you adjust it at the control box? :redface:

 

[Don S]

Re: Volvo Penta 5.7 High idle only when warm

After looking at the control box it looks like I have two throttle cables one that is for part throttle and the other for full throttle.

Yes, you have two cables, one is for shifting the drive, and one is for throttle. Not one for full and one for part throttle.

Post a picture of the insides of the control box. One that shows what the outside looked like would help too.