My 1998 Four Winns had a full tune up and ever since it idles rough. The worst part is that it will stall when shifting out of neutral. It can happen when the engine is cold or warmed up. It makes putting the boat on the trailer a real trial. It's a 4.3 GL (carb not fuel injected). We have raised the idle RPM slightly but that does not help. I have researched possible causes but don't even know if these items are for a carb or fuel injected system. Possible culprits could be: fuel pressure regulator, idle air control, manifold absolute pressure (MAP) sensor. Any input would be greatly appreciated.
Rough idle on 1998 4.3 GL Volvo
- Thread starter jim698
- Start date
- Joined
- Jan 1, 2000
- RO Number
- 2006
- Messages
- 359
The items you listed, fuel pressure regulator, idle air control, manifold absolute pressure (MAP) sensor are used in a fuel injected systems.
Did it have these issues prior to the full tune up?
Good Luck.
Did it have these issues prior to the full tune up?
Good Luck.
- Joined
- Jul 27, 2001
- RO Number
- 5508
- Messages
- 1,243
Who did the tuneup? If it was fine before, and not after, my guess is that they set the timing incorrectly. Or put the plug wires on in the wrong order. Not sure what else you can get wrong as part of a ‘full tune up’ that would cause idle and stall problems. Maybe they used the wrong spark plugs?
Why not get whoever did the tuneup to fix it? Could be a defective part used in the tuneup.or a mistake was made in timing or plug wires. If carb has not been rebuilt in 5 years send it out and get it rebuilt.
Treadwell in Treadwell NY does an excellent job. You can ship it to them.
Treadwell in Treadwell NY does an excellent job. You can ship it to them.
That's what I thought but needed confirmation. Performance at idle was fine before "tune-up"
Rebuild the carb.
- Joined
- Jul 27, 2001
- RO Number
- 5508
- Messages
- 1,243
If the boat ran fine and idled at 650 before the “tune up” my suggestion is to fix what they messed up - check the timing, check the firing order, and check the spark plugs. can you find out what else they messed with? Probably the mixture too.
- Joined
- Jan 1, 2000
- RO Number
- 2612
- Messages
- 832
Exactly.
Had a mechanic set up firing order thinking it was a GM; it was a Chrysler 318.
It took a Chrysler mechanic only a few minutes to figure out the problem.
Had a mechanic set up firing order thinking it was a GM; it was a Chrysler 318.
It took a Chrysler mechanic only a few minutes to figure out the problem.
I don't think I have have ever experienced incorrect firing order, but wouldn't it run rough at all rpms?...same for sparks plugs and even bad timing?? Although I haven't dealt with any other carb since 1976. BTW, thanks for the replies and helpfulness!
- Joined
- Jul 27, 2001
- RO Number
- 5508
- Messages
- 1,243
That’s a good point - if firing order is wrong, it would not run 100% right at any speed. You would be surprised though; i once ran an 8 cylinder about 50 miles on seven cylinders ( long story), and above idle speed it ran pretty good. and if timing is not advanced enough at idle, it may run well enough once rpms force it to advance that it would be hard to notice.
I‘m assuming a full tune up is new plugs, wires, cap, rotor, and points ( if you have conventional ignition). adjust timing, adjust mixture, adjust idle speed. So if it were me, I would start with those 8 things. Most new parts today are absolute junk, so not out of the ordinary for anything they replaced to be defective.
how long ago was this tune up? certainly not out of the question that something totally unrelated is causing your problem. If that’s the case, it gets more complicated ; as you need to check compression, vacum, etc. How new is your gas?
I‘m assuming a full tune up is new plugs, wires, cap, rotor, and points ( if you have conventional ignition). adjust timing, adjust mixture, adjust idle speed. So if it were me, I would start with those 8 things. Most new parts today are absolute junk, so not out of the ordinary for anything they replaced to be defective.
how long ago was this tune up? certainly not out of the question that something totally unrelated is causing your problem. If that’s the case, it gets more complicated ; as you need to check compression, vacum, etc. How new is your gas?
The tune up was a few months ago but the problem was immediate. You guys have got me thinking a bit more analytically now with your questions. The idle is a bit rough (not terrible) but the biggest issue by far is the fact that when I put it in gear it wants to stall. I have to give way more gas than I want to to keep it running. This is especially troublesome when trying to load onto the trailer or any other maneuvering around the docks. It used to be that you put it in gear and simply idled fine and you could accelerate very slowly....not anymore. And to answer your last question, the gas was new.
- Joined
- Jul 27, 2001
- RO Number
- 5508
- Messages
- 1,243
there are probably some good youtubes you can find to check and set the timing - that’s where I would start. If that doesn’t get it done, consider adjusting the idle mixture. You would need a timing light, and to get the mixture right, a vacuum gauge. or if you don’t have the tools, just advance the ignition a bit, you know you went too far if pings at high rpm. And richen the mixture - if you go to far, you’ll probably smell it in the exhaust. Not ideal, but easy enough.
Don’t want to run it too long like this, as it’s probably beating up the drive shifting it at a high rpm
Don’t want to run it too long like this, as it’s probably beating up the drive shifting it at a high rpm
- Joined
- Jan 1, 2000
- RO Number
- 2612
- Messages
- 832
It would start fine and run ok for while, but a mile later it would act up..
- Joined
- Sep 28, 2002
- RO Number
- 10314
- Messages
- 850
This is probably a Holley 2bbl or 4 bbl, depending on the year it could be a Prestolite BID electonic distributor or a Delco EST.
The Holley carbs are not hard to rebuild but I would be checking the ignition system first. When the engine was tuned up did you get a list of parts replaced and what was actually done?
On an engine like this with electronic ignition, all you are really doing is changing plugs (maybe mixed up order of wires on one side) changing the cap and rotor (if it has the crab style distributor cap these have a rep of going bad often) or changing the wires (same issue with possible wrong order of wires in the cap or wires connected to wrong plugs. Then normally you'd check timing when done. Keep in mind that if it has a Delco EST there is a special procedure needed for checking/adjusting timing. More complex than on my old 4.3 with the simpler (and I think better) Prestolite points distributor. The Prestolite points distributor and the Prestolite BID electronic both used a mechanical (centrifugal) advance system, hence no special procedure like for the Delco which uses electronic spark advance. Before touching the carb, go thru the cap, rotor, wire order on the dist cap, and on the plugs.
Plugs on a 4.3 V6:
looking at it from the front....
port side is 1-3-5
starboard side is 2-4-6
The Holley carbs are not hard to rebuild but I would be checking the ignition system first. When the engine was tuned up did you get a list of parts replaced and what was actually done?
On an engine like this with electronic ignition, all you are really doing is changing plugs (maybe mixed up order of wires on one side) changing the cap and rotor (if it has the crab style distributor cap these have a rep of going bad often) or changing the wires (same issue with possible wrong order of wires in the cap or wires connected to wrong plugs. Then normally you'd check timing when done. Keep in mind that if it has a Delco EST there is a special procedure needed for checking/adjusting timing. More complex than on my old 4.3 with the simpler (and I think better) Prestolite points distributor. The Prestolite points distributor and the Prestolite BID electronic both used a mechanical (centrifugal) advance system, hence no special procedure like for the Delco which uses electronic spark advance. Before touching the carb, go thru the cap, rotor, wire order on the dist cap, and on the plugs.
Plugs on a 4.3 V6:
looking at it from the front....
port side is 1-3-5
starboard side is 2-4-6