View Full Version : AQ130C idle down issue

08-09-2006, 06:02 PM
"This has been an ongoing problem for a while and since I've gotten so much other great information and help here, I thought I'd throw it out here to see if anyone has any suggestions...

I've got a V/P AQ130C with the dual, single bbl Solex 44 PAI carbs as seen here: ("")

The problem I'm having is that when backing off the throttle after running, it won't come all the way down to slow idle speed. The engine will slow down but usually it won't go below 1500 RPM despite my backing off the throttle all the way into neutral. Sometimes the RPMs are high enough that it won't go into nuetral, which as you might imagine is not good when approaching a dock, beaching, etc. But, the RPMs will settle all the way down to idle speed if I give the throttle a very short and quick thrust forward and then back. Not being able to get it back to idle speed without this quick throttle action also happens after slow (5-15 mph) speed operation, and not just after running at high speed. I've gotten pretty good at dealing with it, but it's something I would like to get fixed since it's sort of a pain. I keep all the moving parts on my carbs and the linkage coated with a light lubracating spray like WD40 or silicon spray and besides this issue, the carbs seem to be in good shape and working well.

Any ideas or suggestions are welcome!"

El Pescador
08-09-2006, 06:29 PM
"I had occasionally the very same problem in the AQ140A I used to own, which was a OHC engine with dual Solex sidedraft carbs. What I used to do when that happen was to turn off the ignition key and on again before the engine stalled, and that cleared the symptoms (for awhile). I suspected this was caused by the distributor weights remaining open when slowing down and causing excessive ignition advance, so I cleaned the distributor and I did not experience the symptoms anymore. But since I sold the boat shortly afterwards, I am not 100% whether or not the symptoms reoccurred at a later date."

08-09-2006, 06:37 PM
"Thanks, but stalling after slowing down is not the problem here...just the oppposite...it won't back down to full idle after slowing down unless I give her a short, quick thrust on the throttle."

El Pescador
08-09-2006, 06:50 PM
"Bob, I don't think I expressed myself correctly. In my case, when the engine refused to slow down (sometimes it would not go below 1200-1500 RPM at zero throttle), then I turned the ignition switch off; about one second later, when the engine already had lower RPM but before it had stopped completely, I turned the ignition switch on again.

Clear as mud?"

08-09-2006, 06:58 PM
"Clear as Lake Tahoe is in my avatar now!! Thanks for the clarification, El. I will try that next time I'm out. How hard is it to clean a distributor, which I presume also includes some disassembly and reassembly?"

El Pescador
08-09-2006, 07:27 PM
"It is not hard to clean the distributor, you just have to access and remove the points plate (oops, I mean the Pertronix plate http://www.marineengine.com/discus/clipart/biggrin.gif) to access the springs and the centrifugal weights. If you find the springs rusty or the mechanism looks sluggish, you can clean and grease them. Also, you may want to consider taking the distributor to a shop where they can put in on a distributor test machine. This way, they will replace any worn parts and make sure the advance curve remains the way it should be."

08-09-2006, 07:32 PM
"You need to adjust your carbs (needless to say).
Start by removing the flame arrestors and disconnect the throttle cable from the linkage between the carbs. This so you can check the carbs w/o any interference from the shift/throttle lever.

Ensure that both carbs "open" at the same time. This is adjusted via the rod that connects the two carbs. "Throttle action" should have the exact same impact on both carbs.

Then adjust your idle (one adjustment on aft side of each carb's throttle body). You will also need to adjust the idle mix. The screw is found on the port side of the throttle body. Assuming your carbs have the older style throttle body, very gently tighten the idel mix screw, and then unscrew it appr. two turns.
If you have the newer throttle body, you will have to unscrew appr. 9 turns.

The visual difference between the two throttle bodies is tjhat the older style mixing screw sitas at an angle, the newer style sits at 90 degrees and is alwmost flish with its surroundings when properly adjusted (you will not find this in a Volvo manual since the throttle bodies did occur "mixed" during certain years, just before the red inline 4s went away - Volvo's last "real" engine - today eveything is based on GM blocks).

I can send some photos if you like to see this more in detail."

08-10-2006, 12:19 AM
"Per-Ola Selander, thanks for your detailed reply. I have previously adjusted my carbs as you described (I have the older style throttle bodies) with no difference, but I will try again next time I have the opportunity.

I'm not that familiar with the mechanics of the carbs, but I wonder if there is a spring or two that has become tired over the years which are supposed to assist with bringing the throttle back to idle? And by giving the throttle a quick thrust forward and then back, the spring(s) are then able to do their correct job? Just a wild idea... http://www.marineengine.com/discus/clipart/happy.gif Or is the throttle action strictly controlled by the back and forth action of small levers connected to the rod between the two carbs? Sorry, I don't know the technical terms for this and I don't have my Seloc manual handy."

08-10-2006, 02:50 AM
"Hi Bob,
No, you are not that far off. The spring that brings the throttle "axle" back to its idle position sometimes "works their way" into the throttle body housing and it can create problems with treturn to idle. The spring is found on the opposite side (of the carb) of the idle adjustment screw.

I can send a photo from a posting on a Swedish marine forum (photo by Lars Lundblad) and how he solved the problem. He added new return springs to each carb.

Regardless, do all testing with the throttle cable disconnected."

08-10-2006, 02:53 AM
"Looks like I can add the photo here. See if this works...

http://www.marineengine.com/discus/messages/12487/24367.jpgAdded return springs for Solex carbs (AQ170)

08-10-2006, 02:55 AM
"And another one
http://www.marineengine.com/discus/messages/12487/24370.jpgAnother photo of return springs

08-10-2006, 10:16 AM
Thanks Per-Ola. Am I correct in assuming that those silver springs were not OEM and they were added to solve a similar problem like I have?

Can you poost a link to the Swedish marine forum? Not that it will do me much good since I don't speak Swedish but...

Thanks again!

08-10-2006, 01:59 PM
"You are absolutely correct. True "home made" after market parts, and yes, he had similar problems to yours.

I had that as well last week (drew me nuts...) but in my case it was the solenoid valve on the aft carb. that was hicking up. Don't go looking though, it is only found on the Solex on the AQ171A/C and AQ251 engines (all DOHC)

One of the best/most active forums can be found at www.maringuiden.se ("")"