Rough Idle 55 Roadmaster

[1mortician]

Just Got my car back from the shop, where I asked them to do Brakes, a minor tune up, and change all fluids.

Thank goodness the Brakes are so much better, but the idle of the car is now quite rough. I was told that the Carb desperately needs rebuilt.

I trust this mechanic, and I think he is probably right, but I still want to make sure I am not missing anything small on the rough idle.

I have checked the vacuum lines they all seem fine.

How do you visually identify the type of carb this is, I always thought it was a Carter, and I dont see that physically stamped on the Carb anywhere.

Has anyone had any luck with doing a core exchange from Kanter?

I am no expert mechanic by a long shot, I just want to get her running smoothly.

Thank you for all your help!

[JohnD1956]

Was it idling rough before the tune up? Or is this something new since the tune up?

Does your engine still have the spark plug covers on it?

I suggest you get the car in total darkness and idle the engine while looking at the area of the plug wires. Look for small intermittent sparks. Sounds like a bad plug wire may be the fault if the car did not idle that bad before the tune up.

[1mortician]

Thats an excellent Idea, It does still have the covers on the engine. I kind of popped a wire or two off of the dist cap last night, and one gave me a big shock, which I know is not right.

The car did not idle quite this rough prior to taking it in for service, I do know he took a look in the carb so he may have dislodged some crud or something as well. I have also thought about running some seafoam through the car to see if I have any carbon sticking in anything.

Thanks for your tip, and I will do that this weekend!

[NTX5467]

I'm not sure about the attraction to Seafoam, but putting some fuel system cleaner in the tank and then driving it for a 100 miles or so at one time should clean the carbon out somewhat, by "use".

With new spark plugs and better sparks, it might be showing up the possibility that some valves might be on the verge of "burning", which the greater compression pressures might have made more apparent.

Years ago, I discovered the best way to cook the carbon out was to just drive the car for longer distances, even without any cleaner in the fuel system. The prolonged time at full operating temperature and the carb supplying its "main system" fuel in non-carboning doses does work, just not as fast as chemical cleaning might.

People used to add a quantity of diesel fuel to their gas tanks before long trips to allegedly cook the carbon out of their engines. Personally, I feel that something like Berryman's B-12 (quart liquid) or the more recent fuel additives (which have NO alcohol in them) can work equally well. RXP is supposed to be a good one for getting "dirty" engines to pass their emissions tests and doing it quickly.

So, get things ready and take it on an extended cruise on the Interstate at 60mph or more, for about 200 miles total. Bring it home, put some fresh fuel in the tank, and then see how it runs and idles.

Check the dwell setting on the ignition points. With age, the "breaker cam" in the distributor can wear and affect the dwell setting (even with new points). In some cases, although the point gap might be correct, the resulting dwell reading might not be in spec, so you might have to play with it to get it so it's more correct in dwell and point gap both. After doing this, check and reset the ignition timing to specs. Then recheck the carb settings (idle speed and mixture). On older vehicles, doing things in that sequence (points/dwell, ignition base timing, carb adjustments) is critical to making sure everything is as it should be.

So, get it out and drive it, with your choice of fuel system cleaner added to the tank, and then see how things work out. For good measure, having a cell phone on board can be a good idea.

Enjoy!

NTX5467

[Guest NikeAjax]

Once again, I agree with what John is saying; make sure your not getting any cross fire through the plug wires. I fought this for years, before I figured it out, and my friend pointed it out to me. Do you have a Buick manual that shows the way to "route" the wires around each other? You can also get those little dingus clips to insulate the wires from each other; also make sure you have the wires in the proper placement in the rubber "chingadera" on the cover. Most if not all modern mechanics are oblivious to this feature on Buicks.

THE fastest ways I've found to clean carbon out of your car is to use a squirt bottle with just plain old water: invariably someone tells me you just can't do this! As long as the car is warm/hot, it can't hurt anything. Make sure you have your RPM's way up as you squirt it down the throat of the carb. Water will not compress, and when it absorbs the heat of the gasoline detonating, the energy released is amplified many fold, knocking all the crud off the valves and piston-tops. Carbon deposits can cause hot spots, and get stuck in valves. I learned this trick from an old master-mechanic.

Jaybird

[buick5563]

I would not worry about carbon deposits before checking the spark plug wire "weave" that NikeAjax spoke about. It isn't that difficult to do, but there can certainly be crossfire without doing it.

[Guest NikeAjax]

For the carb rebuild, I'd suggest getting a kit, and a: doing it yourself, your manual will tell you how, exactly, or b: having someone local do it. Before I became proficient at working on my own car, I made the mistake of getting a "rebuild" from Kanter: it's a hit or miss kinda thing. Some of the people who do the rebuilds are like Spritle & Chim Chim:

[NTX5467]

The water seems to internally "steam clean" the combustion chambers, but an alternative is what I've seen done many times and a little more "low tech".

With a genuine Coca-Cola glass bottle (that's how far back this goes!), add some water and also some ATF. Probably more water than ATF, as I recall. Shake well. With index finger of the preferred hand, dribble the mixed water and ATF mixture into the individual throttle bores of the carburetor. The engine must be approximately 2000rpm+ so it'll stay running with "the additive" mixture.

You MUST be brave! Plus have a fearless assistant to keep the rpms up via the throttle pedal. It'll sound like the worst detonation you've ever heard . . . not unlike firing a GM diesel off with WD-40 mist after changing a fuel injection pump . . . others might have the urge to RUN, but YOU'll be there right over the engine while all of this is happening. With the ATF, you'll have smoke out the exhaust pipe, too, but probably not with just a plain water situation. Any recommendations of distilled water? What I recall being used was plain tap water (hopefully with few minerals) with chlorine added (do this outside with a breeze!!).

I don't recall this procedure making as much difference in the way the allegedly carboned-up engine ran afterward. But it made for "good show".

A more high-tech way would be to follow the GM TSB on decarboning Cadillac NorthStar V-8s. There is a specific chemical "kit" for this, plus the GM spray Top Engine Cleaner. As I recall, with the engine to operating temperature, you spray the cleaner and such into the throttle body to kill the engine. Let it soak overnight, then restart in the morning sort of thing. Your local Cadillac dealer might have some knowledge of this kit and how to use it.

LOTS of choices!!

As for the spark plug wire issues . . . possibilities exist for crossfires and such, especially if the plug wires have some age on them. With the wires in their various looms, as specified, if the mechanic took them out of the loom for the spark plug change, they probably were bent in ways they hadn't been bent since new, which might have affected BOTH the insulation and the internal conductor, plus them possibly not being put back "as they were", presuming they were correctly placed to start with. This would be an issue with many '50s era V-8s where the spark plug wires were rounted through the valve covers for that "custom look". Worst case scenario would be to get a recently-built set (look for the date code on the wire insulation) rather than an NOS set as you're wanting the "youngest" conductor you can get.

From experience, many people want to go first to the carburetor for rough idle issues . . . even after it's adjusted for its best idle quality . . . when the real culprit could (and usually is) somewhere else. Carburetion issues and ignition system issues can act similarly and ignition system issues are usually the easiest to take care of.

Many years ago, my machine shop operative told the story of a man who had a middle 1970s Plymouth V-8 that developed a miss on the way to TX from "up north". By the time they got to TX, it was a full-blown dead cylinder and generally poor driveability. When Tommy got the cylinder heads to do the valve job, he found out what had happened.

During the long cruise pulling a U-Haul trailer, this was the first time the car had been on the road for that long at a time. The worn valve guides (and seals) had previously allowed oil down the valve stems, where it caked up as deposits on the backside of the valve heads. The steady and continuous cruise situation caused the deposits to break up and go into the combustion chamber . . . some even getting caught under the edge of the valves. After the trip, several exhaust valves were either burnt or getting ready for such, plus a intake valve or two, also--nothing a full valve job couldn't fix.

Investigate the underhood "light show" from the spark plug wires, plus their routing and looming. Do a fresh oil and filter change, add some fuel system cleaner to the fuel tank . . . and drive it.

Enjoy!

NTX5467

Edited June 22, 2010 by NTX5467 (see edit history)

[1mortician]

Thanks everybody for all the tech tips, I am firmly convinced this is in the ignition. I am going to put new plugs and wires on in the next couple of days and route them according to the manual. i will see how that shakes out.

Thanks again for all the help, gotta keep this old girl running!

[Guest NikeAjax]

BTW, 7mm silicone's what you should get: I have some pretty yellow ones that look just swell with the green of the engine. Get some of those plastic chingaderas too, to separate the wires where they touch, just to be on the safe side!

Jaybird

[NTX5467]

You might be able to find the plug wire routing separators on the "HELP" rack at the auto supply. Otherwise, they should be available from the restoration parts industry (at higher prices), usually for non-Buicks or "universal". Chevy used some solid ones that slipped into holders at the rear of the engine and also on the Corvettes with the spark plug wire shields . . . solid looking until you bend them and the slots/cuts show up . . . with a groove to slide into the holder bracket back there.

Keep us posted!

NTX5467

[1mortician]

Got the new plug wires ordered, Im going to give the whole timing thing a try. The separators on the car are old and rotted so I have ordered a new set too.

Anyone know anything about these carbs? The automatic choke is not working.

When I start the car, which has to be done by the pedal, as you know, it allows the choke to slide back, I can hold the choke in place and start the car under the hood. Fixes for this?

Thank you!

Eric

[Guest NikeAjax]

Eric, is your choke properly indexed? Is the butterfly shut tight, or way open? Closed, you should have a gap, just slight. I know I'll catch a rash of $#!t for this, but you can fake it by putting a paper match in there and using that as a feeler-gauge. Pull the cover off the choke and make sure the butterfly moves freely, and make sure your choke-stove is clean, no carbon!

Ummm, does that help?

Jaybird

[NTX5467]

For those that don't smoke, you might find that the flap from an oil filter box might work, as well. KEY thing is that as soon as the engine has run a minute or so, the exhaust heat coming through the system should start to open the choke slowly AND that if you throttle into the engine with the choke still not fully opened, that the additional air flow over the offset shaft/blade will additionally open the choke a little more. Making sure the vacuum passages in the carb (to the backside of the choke thermostat area, necessitating the baffle in there) to draw exhaust gasses through the system are clean and open is necessary, as mentioned.

If you might need to index the thermostat a few notches "Leaner" than spec, don't hesitate to do it, provided the engine will display decent driveability from stone cold with the fuels of your area. The earlier calibrations were done back when all of the "bad things" were in our fuels . . . so they claim . . . without all of the higher aromatics that are now used that can make the earlier calibrations "off".

Just some thoughts,

NTX5467

[1mortician]

Well thats the problem, the Choke is not closing at all, its just hanging there wide open. I can manually prop the choke closed to start the car under the hood, but it will not activate at all.

I dont know enough to get this fixed, I am going to probably take this somewhere. It is a pain trying to find a good mechanic. The last guy I took the car to, pretty much screwed the car up.

[stealthbob]

Well thats the problem, the Choke is not closing at all, its just hanging there wide open. I can manually prop the choke closed to start the car under the hood, but it will not activate at all.

I dont know enough to get this fixed, I am going to probably take this somewhere. It is a pain trying to find a good mechanic. The last guy I took the car to, pretty much screwed the car up.

Find some old mechanic somewhere...

...then ask if his Dad is available for some carb work

[NTX5467]

With ambient temperatures above about 70 degrees F, the choke is really not needed. Normal accel pump shots should provide enough enrichment to get it to fire off, usually.

The "shadetree" method of getting a baseline automatic choke adjustment is to have it JUST close at about 70 degrees F . . . not just air temp, but the temp of the car's engine (as in sitting unused during the day and fully cooled down). From that "barely closed" setting, the vacuum assist should pull it open a certain amount as the engine starts, then the heat coming through the heat tube should finish getting the choke fully open.

On my normal, daily car, I have a 4165 Holley carb. This particular one is a little more tricky to get the choke thermostat set than the other ones I've had, or it could be the recent changes in fuel content. Either way, during the winter I have to back it off more than normal so that it does not load-up until it gets warmed up OR I get it to the Interstate. This last winter, I backed it off enough to make it non-functional (it's an integral, electric assist choke).

To my surprise, I only had to give it a few short pumps, fire it off, then keep the idle speed up a little with the throttle, and it drove pretty well. I just left it there. This is not the way things are supposed to happen, but it did. How much Rotella synthetic 5W-40 oil might play in that deal is also open for discussion, rather than normal non-synthetic non-multi-weight oil. Or the fact that the engine has aluminum cylinder heads (which do let the heater get hot quicker) rather than cast iron. Several factors that could have affected the way things work together.

But until you can get the ignition system upgraded with new wires and such, don't be messing with the carb that much, other than to get it to run better in the short term. Getting the choke to work would be in that mix, too, but be ready to do a little more re-tuning of the carb when the ignition issues have been addressed and taken care of.

Just some thoughts,

NTX5467

[JohnD1956]

Can't agree more with NTX. One thing at a time, Otherwise you won't know what fixed it. I started my cold 56 for years from under the hood. I just looked at it as a way to show off the engine compartment.

[1mortician]

Yeah, it wont start even with a few pumps at all. who knows?

I am going to start with the plugs and wires get that done at least. It is running really rough, and I think it has to be ignition.

Just keep plugging away at it.

[JohnD1956]

Another thing to look for is cracked wire insulation on the wire from the coil to the distributor. And inside the distributor too. But did you ever look at the running engine with the car in total darkness to see if the wires are arcing?

[Guest NikeAjax]

Eric, do you have a manual for this??!?!?!?!?!? If you don't, please get one; no, I'm not trying to lecture you, that never helps anyone... If you want to tear down your own carburetor, which I'd highly suggest doing once you get the ignition figured out, it will virtually walk you through the job. These old carbs are pretty simple. If you're terrified of the thought, don't be: just take lots of digital pictures! "Use the Force Luke..."

From my experience, it's usually one of two things, once you get everything cleaned up, dirt can cause lots of rage, the accelerator pump, and the needles and seats with the float levels.

You might also have bent linkages somewhere, but that's usually easily seen/fixed once you get the carb off, with a needlenose pliers. If and when you get stuck, one of use can walk you through your questions.

Jaybird

[carbking]

Eric - there is a little information about automatic chokes here:

THE CARBURETOR SHOP / Automatic chokes

Jon.

[Guest NikeAjax]

Eric, I just thought of something! With your new plug wires, leave the covers off for the time being and just drape the wires off to the sides of the block, if that gets rid of your miss/missfire, that should help with the diagnosis!

Jaybird

[JohnD1956]

Good one Jaybird. I'd concur totally.

[NTX5467]

Yes, if the wires are un-loomed, it should get rid of any possible "inductive missfire" from wires not being in the correct looming orientation. It might not get rid of missfires resulting from poor internal conductor or external insulation (small cracks) condition situations--might make any current situations, in these areas, worse).

Inductive Missfire can happen even with plug wires which are new or otherwise in good condition, but it might not be a full missfire situation, just a minor one.

Just a thought,

NTX5467

[Alfa]

Whilst I agree with all the previous comments about avoiding crossing plugs leads, have you checked that the leads are on in the correct order??

I say this because, as I understand it, the problem arose when the car had been in the workshop. It is very easy to have a couple of leads fall off and to reconnect them in the wrong order.

I once bought a 1960 electra, which ran roughly when i got it home. The seller had just fitted a new cap and leads and 2 of the leads were crossed over, So, in effect, I had a V6 Buick.

To check, turn the engine to TDC on No1 cylinder ( the marks on the front pulley will align. Ensure your are on the correct rev by lifting a rocker cover and watching the rockers. When 8 is rocking, 1 is firing). Next, remove the distributor cap and check which segment the rotor arm is pointing to. That should be number 1. Check that it is. Then noting the direction of rotation of the distributor, count off the firing order and ensure that the leads are connected to the right plugs.

You should also check the CB points if they ahve not been done lately. You will never be able to set up the carb until the ignition side is correct.

Adam..

[1mortician]

Well, it looks like I am the worlds worst mechanic.

HA!

Today, I decided I would just play around and see if my new "mechanic" had correct advice. I took the air cleaner off, checked the Choke setting, noticed it had been turned all the way around once, so when I put it back to the proper setting the choke closed appropriately.

Next I thought, well if this was that simple lets see how badly the carb needs rebuilt?

Fired up the engine four shots of carb cleaner the roughness settled completely down. You could "balance a quarter" on it now.

So yes, I totally need to put in a set of new plugs and wires, but? A rebuilt carb maybe can wait, and I am happy not to be jumping around at stop lights now!

Thank you all so very much for all your tips! this is one of the most valuable resources for my car. You are all very kind, and not demeaning while I am trying to learn my way around this old girl.

Thank you again!

Eric

[1mortician]

Eric, do you have a manual for this??!?!?!?!?!? If you don't, please get one; no, I'm not trying to lecture you, that never helps anyone... If you want to tear down your own carburetor, which I'd highly suggest doing once you get the ignition figured out, it will virtually walk you through the job. These old carbs are pretty simple. If you're terrified of the thought, don't be: just take lots of digital pictures! "Use the Force Luke..."

From my experience, it's usually one of two things, once you get everything cleaned up, dirt can cause lots of rage, the accelerator pump, and the needles and seats with the float levels.

You might also have bent linkages somewhere, but that's usually easily seen/fixed once you get the carb off, with a needlenose pliers. If and when you get stuck, one of use can walk you through your questions.

Jaybird

I do have the manual Jay, and I am reading it now religiously. I will readily admit I am afraid of tearing something up, haha! I dont want to blow up my 20K investment (which by the way never escapes her memory)

[1mortician]

by her I mean the wife ha!

[Alfa]

Eric

I am so pleased that you have got the old girl running again. These things are usually quite simple to fix, but it is the diagnosis that is the key thing. There is a wealth of experience on here to help with that though.

I cannot over-emphasise the importance of maintaining the ignition system. If you do not know the provenance of the plugs, points, condensor, coil, cap and leads, I would suggest replacing them all. The points and ignition timing must be carefully set of course, but once done, you will have a car that starts instantly and a sound basis for setting up the carb and everything else.

I find coils tend to degrade progressively over the decades, so it is worth changing it if it is old. It sharpens an old engine up no end to have a good strong spark again. The ignition parts are not expensive (no need for specialist parts, your local motor factor can help) and well worth the modest investment. As is a strobe timing light/tachometer if you do not have one.

You will get lots of advice on here about setting up the timing if you need it.

Adam..

PS. I just checked out the pictures of your Roadmaster. What a lovely car !!

Edited July 2, 2010 by Alfa (see edit history)

[NTX5467]

From my observations of recent point-ignition parts . . . other than the points (which usually do NOT come with the vial of grease for the rubbing block as they used to), replacing just to be replacing and know they are now "of known quantity" . . . in many cases, the new replacements might not be of the same quality as the ones on the vehicle.--especially in rotors for the distributor.

To me, unless there is a definite reason to replace the ignition cap . . . such as carbon tracking or cracks in the cap itself, just getting a broad-blade flat screwdriver and gently knocking off any desposits which might be there is good enough. On the rotor, check to see that the center "prong" has a good spring action and is not burnt through; on the outer electrode, you can scrape it to clean it up (many usually have a saw-tooth type end of the center electrode rather than just a smoooth surface) and possibly sharpen it up a little with a point file. When looking at a new rotor and then putting it beside one built 15 years ago (normal, replacement brands), the newer ones definitely look much "lighter" and such. These little clean-ups can save money and usually result in the same performance level as new parts would. BUT if you can find the better parts to match what's on there (rather than the lighter-weight stuff), that would be a move.

Still, though, the orientation of making sure the spark origination location is letting all of the spark energy into the plug wires never can hurt, even with the flilmsier parts.

On coils, it seems that the later ones you can buy from the auto supply stores are all "generic" with "Made in China" stamped into their bottom surface. No more "Delco-Remy" stampings on the coil's outer cover. Might do better to get one from MSD or similar, but not their 50KV coils as that kind of energy is not needed to fire the plugs on your engine. Even if it CAN produce 50KV, it'll only produce as much spark energy as it takes to fire the plug. BUT in the aftermarket, something of that nature might be all you can find, so it won't hurt anything, just cost a little more money.

Using a good quality carb cleaner sprayed through the carb with the engine running can do several things--clean the carb's throttle bores and such, plus help get rid of any softer carbon in the combustion chamber. With the engine on fast idle, spritz some cleaner in short bursts into each throttle bore, several times. Then a 30 minute highway cruise might be in order.

Thanks for the update! Sometimes, the best fixes aren't nearly as involved as might be suspected. Think "Simple things first" . . . Many times, people go for the "worst case scenario" in their diagnosis rather than trying a few simple things first (like the carb cleaner). In reality, you'll never know where you're going to end up, which makes the simple things first more valuable actions.

Enjoy!

NTX5467