Car engines and misfire everyonce in awhile.

[JIPJOBXX]

Well my old Dodge is up and running and thought I would just ask one question that has been bugging me for the longest time. My car runs just fine but at ideal it tends to misfire every once in awhile. Its not bad but I was just wondering what to look for with this problem. At cruising speed there is no problem and maybe this could be the nature of this car. Everything is set to proper tolerances as far as the ignition goes and there are no vacuum leaks that I can detect. Could this be a problem with the valves tappets not being correctly adjusted? I have adjusted them twice now in the last five years and they were set at what the factory called for. Any hints on what to look for would be greatly appreciated. The car starts right up and runs like a hot rod with the new advance (Yea oh sure a fluid drive car:() But anyway if I cannot figure it out than I might just try to find a mechanic that knows these old cars and have them check it out. Other than this little miss fire it runs great!!! Thanks for all your help and that even goes for Don!!!!! Jon

[greg g]

Open the hood at night and look for stray sparks.

[JIPJOBXX]

Great idea! Thanks Jon

[JIPJOBXX]

Well god decided to let it stop raining outside so I tried that trick on checking to see if any sparks were occurring while looking down at the engine and none spotted. I had this brilliant idea maybe I might just make a little movie with the engine running and let you guys here what it sounding like. I hope its not a valve problem and tomorrow I will recheck the compression ratio. If it has a bad valve than maybe that would cause it to misfire. It not all that bad and at a high idle it seems to go away or its not as noticeable. I have had this slight miss ever since I been driving the car and I thought while it was winter I could figure it out. It has new everything electrically from rotor cap to wires to plugs and all the rest of the stuff that makes an ignition work. So tomorrow I will check the compression again!!!! Wish I knew a real good mechanic that knows these old sixes but I don't think they are alive anymore around here. Before I get oft this subject my ignition wires are kind of a strained material and do not have any copper wire running through them. Could this be the trouble?

[JIPJOBXX]

I just read in the Seach section about another party having a misfire like mine so I think I will try all those solutions that were suggested before going any further. But would like to know what is the proper ignition wire material to use on our old cars.

http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=28448&highlight=misfire

[Don Coatney]

I hope its not a valve problem and tomorrow I will recheck the compression ratio.

How are you going to check the compression ratio? Remove the head and CC it?

If it has a bad valve than maybe that would cause it to misfire.

Have you done the dollar bill test?

It has new everything electrically from rotor cap to wires to plugs and all the rest of the stuff that makes an ignition work.

What are the numbers you used when you set the new vacuum advance curve? Where does your advance start, and where is it full in? Improper adjustment of this curve can and will have performance issues.

...

[JIPJOBXX]

Well I have a compression gage and that will do the trick for testing the compression. I forgot about that old trick with the dollar bill Thanks! I will try that propane trick for testing to see if there is a leak at the intake inlets also. The car seems to have more power now as I took it out for a spin and nothing is lacking there. I haft to find someone with vacuum testing rig as I kind of do not want to spend that kind of money for such an item. But I have lots of friends who are into cars and someone must have one just sitting on there work bench. I have never done that propane test and it sounds like if my engine starts to run with no miss I will let you guys know. About the ignition wires as I mentioned they are some type of carbon filament and I was wondering if that was the proper type. Oh one more thing my number six plug the one next to heater valve shows sign of rust on where it screws into the head and I will clean that up and test that plug today. Thanks for the help and will continue upward and backwards!

[JIPJOBXX]

Oh one more thing what is the proper torque for the exhaust and intake manifolds? And what would be the pattern for tightening thees items?

[claybill]

HEY JIB...... i would go and look for a copper wire for the plugs. some say the old ones a usually better than a new filament set. a slight miss is noticeable at low speeds high speeds you wont notice it.

i bet it is electrical.

[JIPJOBXX]

Yea I think I will buy a set of copper wire ignition wires today!

[Jerry Roberts]

Oh one more thing what is the proper torque for the exhaust and intake manifolds? And what would be the pattern for tightening thees items?

You can't get a torque wrench on most of those fasteners . Just do it by feel , not too tight , not too loose . I would start at the center and work towards the ends ( like the cylinder head ) and go over them more than once .

[JIPJOBXX]

Well did the dollar bill test and the valves seem to be in good shape! I removed all the plugs and checked them out and there ok! Set the breakers to the proper dwell setting. I just about went over everything and even did that spray test on the intake manifolds and no difference. But I noticed when I returned the distributor for timing the vacuum went up almost oft the scale on my vacuum gage. So its running great and it does seem to have more power but still it has that persistent misfire every once in a while. Tomorrow before the Turkey feast I will do another compression check and then see what all the cylinders are running on. I do have kind of wired carburetor just set up for fluid drive and I might just check that out again. It has two plungers inside the body one for running the car and one for idling with the fluid drive transmission. I have another rebuild kit and so I might just rebuild that one again and see if I mist anything the first time I rebuilt it.

[Niel Hoback]

Just for me, back the idle mixture screw out 1/2 turn and see if it makes a difference. Wait until its warmed up first.

[1941Rick]

switch to electronic ignition....gets rid of the little gremlin

[JIPJOBXX]

Niel I will do that tomorrow first thing and see if that makes a difference. I might just pull the distributor out and check shaft bearing wear although I'm pretty sure that ok but the book states it cannot have more than .008 allowable wear. Oh I did notice one thing today while adjusting the points to the proper dwell setting that at 38 degrees it was running kind of rough but two degrees less I could tell it smooth out but still had the miss. Anyway I'm just having fun figuring this out and hay its a peace of metal and it was made by man and I figure I should be able to fix it!!!

[JIPJOBXX]

The gremlin strikes again and if it wasn't for bad luck I would not have any luck at all. One of the guys on this site made mention to readjust the ideal screw and this is what I found!!!!! Could this be the reason it has a mis? I wrote to him oft line and this is what I said.

Ideal adjusting screw

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Niel this is Jon and you would not guess what I found out while reading your idea for adjusting the Ideal jet screw!!!! When I installed the carburetor many years ago and was not so technically savvy I did not notice that the Ideal jet was broke oft!!!! I went outside yesterday to adjust that jet and kept on looking for it but to no avail. So I went back to my repair manual and sure enough there it is suppose to have one but somewhere over time that jet got broken oft and so I never looked for it when I installed the carburetor. So now I haft to take the carburetor oft and have a machine shop drill out the broke of screw and install a spare one that I have. Maybe this is the problem??? It was broke oft so clean that you would think that it never did have one. But I recheck with my manual and sure enough there is one!!!!!! Why I mist that step in that adjustment is beyound me but now its time to remove the carberator and get that fixed. Thanks for thinking about me and my old car. Jon

[JIPJOBXX]

Does anyone here have a base for a BXVD-3 carberator? I need one and will buy it and pay to have it shipped.

[JIPJOBXX]

Oh remember I have been driving this car for years and always had this miss problem but never got around to trying to get it fixed-just lived with it. Car has always run fairly well at highway speeds and started right up but maybe just maybe this is the solution to the ideal and why it misses?

[JIPJOBXX]

Got the carburetor oft and thought I would haft to take it to a shop and have them drill out the needle valve but I lucked out and was able to back it out using a very small screw driver. So now I have installed a new needle valve and just wondering if I want to go out an play on the old car or watch a football game. Think I will watch a football game and play with the carburetor latter on. It will be interesting to see if this was causing the problems but I don't think so but maybe????

[John Reddie]

Jon,

The idle adjustment at the carberetor base can most certainly affect the smoothness of the engine idle. This could very likely be the cause of your trouble. Good luck to you.

John R

[JIPJOBXX]

Well in a few hours I will have the carburetor back in the old Dodge and we shall see what we shall see. I'm going to try and find a garage with an old oscilloscope for checking out engines and maybe just maybe they will find that darn miss.

[JIPJOBXX]

Well all back together and it still has that miss but with the adjustment with the non broke oft ideal screw I can adjust it to run at about 300 rpms and ideals good but still that persant mis. Going to call a few shops around here and see if they have the old style scopes for testing engines and see if they can find this mis. Jon

[1941Rick]

Does it miss under acceleration?

[JIPJOBXX]

Yes but more so when it idling. I checked the compression this afternoon and here is what I got.

1. 120

2. 115

3. 130

4. 125

5. 125

6. 130

And if Don is looking in do you have a way of checking out the shaft in the distributor for bearing wear without taking it out? The tolerance is -.008" I thought maybe I could just put a feeler gage between the points and see if they are reading the same on all eight lobs. I have two spare distributors from different years of Dodges and the shafts look to be the same and I can swap out the bearings and shaft from one of those. Just wondering if I haft to take out my distributor again and put a dial indicator on the lobes and take a sweep around to see if maybe the bearing are worn out in distributor and causing this miss. Do you have a photo of the distributor taken apart as far as the shaft?

[1941Rick]

You need to find a shop that has a tune up scope to check the ignition system. Could be wires, plugs, point, condensor or the coil...a scope will tell you right now. Your compression is good.