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#1
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My car is missing.
Hey guys its not what ya think. My car is here with me. The problem I have is just yesterday my car was running fine and it has been for about 150 miles since I brought her out of the garage back in late April. Well I was crusing down the highway and I noticed that my car seem to be acting sluggish. It has aquired a slight miss and seems like its running on 7 cyl. With the 508 purple cam it seems to idle ok and starts up and shuts down fine. It only misses when you accerlate.Thought I may have a fouled plug. I had just this winter put new plugs in so I pulled all the plugs and they were all fine,even the resistors were white. I double check the gap and all were at .045 right where I had gapped them. My spark plug wires look to be in good shape. I examined every one and two of them have a slight rub mark from my valve cover and one from my throttle linkage on them but I dont see ark jump which I checked at night time in a dark garage These wires have been on the car for 4 1/2 years. I have not checked the "D" cap yet. The cap and rotor was new 2 yrs ago along with the Blaster SS Coil. So my question is, before I start tearing into things, even though wires look good could there be a break down in the wires from all the heat that I cant visually see or feel? I am running 340 c.i. .030 over with MSD 6A, 509 Mopar purple cam, Headers, and I know the wires get a lot of heat. Can the Blaster Coil be causing this problem? Or how about the rotor / cap? Previously it had a tan cap but this one is black. Any difference between the colors? A friend of mine is leaning towards the spark wires being weak. What do you guys think the problem may be? Any feedback would be greatly appreciated.... Thanx
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#2
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Yes the plug wires can be bad and still look good. Had that problem with my MP wires that I had on my truck. You can measure the resistance of the plug wires but that doesn't always show they are bad. 10,000 ohms per foot is the limit, but I'd compare them to each other.
Can you feel the miss if you load the engine (holding the brake and giving it gas when in gear)? If you can then get an assistant and some insulated pliers and start pulling one wire at a time till you find the cylinder which you have no change. That will be the cylinder that is missing. I actually got an oscilloscope so I could track down my miss. You could also have a lean misfire. Your plugs shouldn't be white. They should be a light tan color. Cap color doesn't mean anything. It's the terminals inside the cap. You want brass ones not the cheap aluminum ones. |
#3
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I don't have the fancy equipment...........
If you have a miss, you need to pull the wires at the dist. untill you find which cycl. is not fireing properly. At that point you have two things to look at. IF it is getting spark at that cyc, then you look to see if the cam is working the valves to the engine. Good luck.
Warning! if you pull the plugs at the spark plugs, you will get your ass jolted like a boxer in the ring when he is fighting. |
#4
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Tech Question
don Tackett, Virgie, KY, 1972 dodge charger, 400 I have a 400 dodge motor that has every thing it is new cam, lifters, everything. I have a bad miss and popping from the carb. What could be my problem? I'm about ready to give up on it! Don, 99% it's a timing problem, valves or ignition. Since this is all well known, I'll just briefly go over the concepts. First, check the accuracy of the TDC mark using the "positive stop" method. Then be sure the ignition timing is set to around 30-35 deg. BTDC, at 3,000 RPM, with the vacuum advance temporarily disconencted. And be sure the plug wires are connected correctly - in the correct order! If this doesn't fix it, it's a valve timing problem. If the cam is near-stock, you can use the service manual procedure to check it. But, since this is really the only other likely possibility, just pull apart the front of the engine and check to see that the timing marks on the cam and crank sprockets are correctly lined up. Aslo, be sure that the locating pin has not broken off the camshaft....remember, it's only bolt torque that keeps the sprocket correctly positioned to the cam. If the bolt isn't torqued to specs, the sprocket will snap the pin in a second and destroy the cam / crank timing relationship. Rick (Mopar Action) |
#5
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Well before I get into tearing this and that apart I think that I am gonna replace my cap and if that isnt the problem gonna try the spark plug wire elimination theory next. Removing one plug wire at a time. I honestly dont think that anything has snapped as the engine doesnt spit and sputter. I once had a BB mopar and it jumped timing and it did nothing but spit , sputter and back fire and had very little power. I have about 90% power right now. Thanx guys for the feedback. I will keep all informed when I find out the problem.
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#6
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Cap color
Does in fact make a difference. The tan colored cap from Mooar is made from Alkyd material, which has higher resistence to arcing. I would suspect in your case that you have a bad wire. Put some Taylor 8mm wires on it and you might solve the puzzle.
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#7
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Another way of spark elimination is instead of pulling the wire take a test light ground the dumb end and then insert the probe between the boot and wire. I've seen people pierce the wire itself but I wouldn't do it. It work good and doesn't harm the test light and works just like taking the wire off but without as much of a chance of getting zapped
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#8
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I have never seen a plug on a cylinder that is missing that is not a different color than the rest. In your testing around make sure that you didn't cross 5 & 7 plug wires. Very easily done and the symptoms you describe fit to a T. Barely perceptable miss at idle being right next to each other on the engine and fire in direct sequence but will be definitely there under load.
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#9
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First 0.045 may be a bit much on the plugs. I would try 0.040 and see if the miss goes away. The concept is to open them up 0.005 at a time until you get a miss and then close them down 0.005
Also, high output coils (particularly msd's) have a tendency to overheat and breakdown from low speed (constant driving under 3000 rpm) operation. MSD coil two years old hmmm? The combination of these ie, the plugs too wide (possibly just for a failing coil)and the coil breaking down causing the miss may be your issue. |
#10
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Quote:
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#11
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Taylors [cut to fit]are great wires that really last and don't break the bank.
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#12
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And by the way....
If you have headers, especially, with it running rub the plastic handle of a screwdriver on each header pipe at the head, if it slides like butter on a skillet it's firing, if it sticks/drags it's dead. |
#13
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Quote:
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#14
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Maybe
It's always a pain putting boots on. My trick is to put a strong length of string through the boot, tie it onto the wire in two places, lube with Armorall, and pull it through.
Taylors are strong enough to handle it. |
#15
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I have Accel peg leg and the instructions are to put the terminal on the wire first then feed it thru the boot. I tried w/o the terminal on the wire and that was no fun either. A string? Hmmm trying to figure how I could keep it from coming off of the wire....Hmmmm I have a thought, gonna run out and give it a try... Thanx peg
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#16
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Well just got thru swapping out the black D-cap back to the Accel Tan cap and the engine does seem to run a bit smoother. Sitting at an idle in park and reving it up there is no noticeable miss,the "R"'s really climb, only when in gear starting out and going down the road there is a miss. I am now definetly leaning towards the plug wires, like a lot of people have said. I dont know if this has anything to do with it or not but in the past I have always cleaned the plug wires with a rag and a little kerosene, takes the grim and so forth right off. Now I am wondering if kerosene has penetrated the wires and this is what could be giving me problems. I will find out once I get them assembled.
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#17
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Are you real sure that you don't have a vacuum leak??? All open carb ports capped and all open intake ports capped???
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#18
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Yes pu
There is ALWAYS ONE story that is used to discredit good/useable information. Try to find something positive to add, might be a bit more challenging? Is there another full moon this week? |
#19
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Quote:
Why are U offended and implying what I said is wrong? Saying .045 gap will trash a coil is bogus, like just fishing with no hook. Oh and thanks for the lame insult, P U, ha ha your funniest .. thanks friend. |
#20
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Do you get a pop through the carb at all?
what carb? what timing? with vac advance? it could be lean surge. |
#21
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If not the wires...
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#22
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I really don't think that there is a benifit from running a wider plug gap, unless your running and excessively lean mixture. Plug gaps in the '60's and early '70's were 0.035" it wasn't untill the late '70's that the plug gaps were increased to help light the leaner and leaner mixtures. I run mine at 0.035".
My Blaster coil is 9 years old. The Mopar Performance wires are also 9 years old but 1 has failed and I'm sure the others aren't far behind. |
#23
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Quote:
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#24
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Cudabob-
I'd like to see the Dyno results on that. |
#25
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Quote:
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#26
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Leige
Then go the other way for a try. |
#27
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Yes aarracer I plan to do that also...
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#28
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Update: Well guys time to put your brains to work. This is a strange problem. The small misfire is still present. After further engine check, I have found that cylinders, 7 & 8 are both running cool with #8 plug being some what damp. We used an infered thermometer checking the heat on the headers right as they exit the head and cyl 8 temp around 300 with cylinder#7 being around 350 while all the others are runnning anywheres from 550 degrees and higher. Done a compression check and have 145# in both 7 & 8. Did a check on a couple of others and they are in the same range. Check the spark and it's ok. So now were thinking that the distributor, which is stock w/o points, may be bad so I bought a Pro-Billet MSD distributor and does seem to run a little bit better but not the way it has in the past. Timing where it seems to run the best is about 10 degrees advanced. All electrical components have been replace except for the coil and we swaped it out with another one, same results. We do not have any idea where to look next. Think I am gonna tear the valve cover off and see whats going on with the valve train. Anyone have any further thoughts or ideas? Sure would appreciate it.
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#29
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It sounds to me like a vacuum leak effecting only those 2 cylinders. What intake are you using, is there a power brake vacuum fitting at the rear of the manifold?
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#30
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DJM it has an Air gap intake and no power brakes.Only vaccum lines are on the front of the carb and they are blocked off... No other vaccum on the car.
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