Bad idle ( surging up and down)

Pipedreams · **Joined:** Tue Mar 29, 2011 6:19 pm **Posts:** 99

EFI 5.7 volvo having trouble ideling, surges up and down almost stalls but catches itself, seems fine soon as you take it off idel?? Any ideas

psusound · **Joined:** Sat Feb 04, 2012 4:08 pm **Posts:** 69

IAC? Idle Air Controller.

acguy · **Posted:** Thu Jul 17, 2014 8:39 pm

What kind of spark plugs do you have in it?

Pipedreams · **Joined:** Tue Mar 29, 2011 6:19 pm **Posts:** 99

Not sure what kind of plugs , but there new the marina just put new ones in. Also my 2 beep alarm stopped working when you turn the key on not sure if these could be related. What are you thinking with the plugs?

acguy · **Posted:** Fri Jul 18, 2014 6:14 am

I had that issue one year when I owned my sundowner, it was a 5.7 GLi. I put in NGO plugs and had nothing but issues. I switched back to AC Delco plugs and then my idle surging issues were gone.
As for your warning beeps maybe they knock a wire off when they were down in the bilge working

rpengr · **Posted:** Fri Jul 18, 2014 6:51 am

psusound wrote:

IAC? Idle Air Controller.

+1

flaMtneer · **Posted:** Mon Jul 21, 2014 8:45 pm

I had this same issue after having the throttle body rebuilt. The idle would surge up to 1500+ rpms then drop down to a near stall. The bad news is that no one was ever able to figure out the root cause. They ended up replacing the entire throttle body and the problem stopped. Boat runs perfect now, but it was a real PITA getting solved. I agree with the post earlier to start with the IAC. I hope it goes a lot smoother for you.

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

That makes me remember something I had forgotten:
If you're left scratching your head, and it still runs like dookie, chances are good that the throttle body base gasket needs to be replaced. My '87 454 Suburban had this issue, and it took me almost 3 days to track that one down!

bigdog347 · **Joined:** Mon Jul 28, 2014 11:10 am **Posts:** 12

This is a classic Vacuum leak symptom on fuel injected engines. use carb clean or propane and spray the intake and TB with engine running at idle, listen for RPM increase and you have found your leak I know the post is old and the problem is most likely fixed, I just want others to see this if they search the forum for idle problems.

Fixer.5 · **Joined:** Mon Jun 02, 2014 12:43 pm **Posts:** 19

bigdog347
I'm having a similar problem,in that my 2000 H230 5.7 gsi with TB fuel injection is surging up and down at about 800 rpm to 1000 rpm as i increase the throttle. When i'm above that it runs smoother. I cleaned the TB with carb cleaner with no change in operation. Someone posted the IAC valve, I think the vacuum leak at the gasket could be my issue.I'll give it a try! Thanks.
Fixer.5

bigdog347 · **Joined:** Mon Jul 28, 2014 11:10 am **Posts:** 12

No problem...let me know what you find. I do want to add that the newer ECM's may adjust the idle to fast for you too hear the RPM increase so it may be necessary to unplug the IAC and hold the throttle open just enough to idle. (this would take the ECM's idle control out of the equation.)

ric · **Posted:** Mon Aug 11, 2014 8:28 pm

psusound wrote:

IAC? Idle Air Controller.

+2

Fixer.5 · **Joined:** Mon Jun 02, 2014 12:43 pm **Posts:** 19

bigdog347
Thanks for that reply. It idles okay. When i'm under way i can hear the engine surge up and down, I can also see it on my tach.
Also re yr comment re newer ECM I don't think a 2000 H 230 could have one.

Rgds

LivinnSadley · **Joined:** Tue May 29, 2012 12:47 pm **Posts:** 38

My boat was doing the same thing but I have a '93 OMC. It was common for the OMC's (Ford) of that era.

You need to see if your motor has a TPS (Throttle Position Sensor) This analyzes your air to gas ratio to your throttle body. If it is not working correctly the motor tries to compensate and over compensates with too much air or too much fuel and that's where the surging comes from.

I think my TPS cost $25- $30 and is easy to replace yourself.

www.iFourWinns.com

Bad idle ( surging up and down)

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