Help with misfire
- Thread starter euroz06
- Start date
BLK 68 R/T
Well-Known Member
Okay. Here’s my 2 cents. You can’t just swap wires like that. There is only 2 ways they can be, right or wrong. You can’t have them all okay except for two and expect it to run good.
That cap looks like it has dirt tracking in it to me, maybe even cracked.
New cap and rotor and then verify motor is at TDC on the compression stroke. #1 should be somewhere close to the 5 o’clock position where the distributor rotor is pointing. 1-8-4-3-6-5-7-2 wires go on CCW there.
Lots of good advice here but toolman Mike said it best, Don't overlook the obvious. The reason those carbon tracks are on that terminal is because the Ignition could not fire that plug, whether it was a big open in the plug wire or a bad plug that won't fire, It's creating extra voltage and trying to find ground. The ignition is doing its job, sending out high voltage, trying to find ground.
Check #5 & #7 in particular - easily mixed up.
euroz06
Well-Known Member
hi, so let me clarify: before this event car ran fine for about 10 years. The wires on the distributer are marked to cylenders (has little plastic strips on it with cylinder numbers). I was able to pull up engine firing diagram and i have confirmed, there are no mixed wires. I swapped wires from cylinder 1 and cylender 3 (just to clarify: i took the wire marked cylinder 1 on the distributer, that is connected to a spark plug on cyl 1 on the car, and i removed it from the distributer and connected it to cylinder 3 at the distributer and connected it to the plug on cyl 3: hopefully this clarifies it. i am not a complete idiot). However, that was done while i was doing every other thing as well that i descibed in my previous post, so i have no idea which step had fixed the missfire.
I am not a mechanic, and I dont know old cars (its easier for me to scan a modern car and the scanner directs me where the issue is). Thus i came to this forum to get advice. Unfortunately, in my local area there are not many shops that know how to fix these old cars. I live in Miami. They either deal with modern cars, work trucks, or those that do fix older cars ask for a blank check (i.e. i go in there with this, they will strip me naked and ask for 5-10k for repairs). It took me 7 months to get my dif repaired, because there is only one guy in the 100 mile radius, and even then, he fu*cked in up the first time, had to redo it, and i dont think he did it well again (and im out $2k). In another case I had a shop replace my fuel float, but they didn't bend it correctly (which from my understanding they really should have known this), so my fuel gauge is off (they refused to fix it, they just said old cars are like that). There are a lot of examples. Once i figure this out, the car is going for sale. I don't have any mechanics here and its an old car that i am unable to care for properly.
So again: I replaced the spark plugs (gapped at 0.45), I replaced the distributer cap, I replaced the rotor. All these were due to be replaced. I cleaned up inside the distributer with the electrical cleaner. I took off every wire sprayed electrical cleaner in there and ensured they fit nice and tight. I went for a drive, car was running better than ever at low rpm (before 2.5k) but rough at high rpm (3k and above) and was getting a lot of pops/backfire (never did that before. Spark gap was 0.35 on the old plugs, could the higher gap cause backfires). I went to adjust the timing (ive marked the original location), with the engine running, i turned it counter clock wise a little and went for a drive, car ran much worse at low rpm. I then adjusted it clockwise a littel (adjusting it a lot I would hear knocking, so i tried to adjust clockwise just enoguh so that i can't hear the knock). The car runs amazing at low rpm, as in i now have more power in low rpm than before the issue (feels like im up like 20-30hp). After 3k rpm it runs intermitten, i.e. not a clean pull in the rpm range. I do however have loose belts (they stretched and i have no more adjustment on them, i've ordered new belts). Could the loose belts cause poor performance after 3k rpm (they start to make a horrible squeel at 3k)? or am i still dealing with bad wires/distributer? Ill swap the belts when they come wednesday, to see if it improves. If not, ill order new spark plugs wires. If that doesnt' help, ill order a new distributer.
Am i right to assume:
A. it could be loose belts?
B. it could be that wires internally are just "gone" due to age (10yrs)?
C. Distributer is too far gone/internal problems?
I am not a mechanic, and I dont know old cars (its easier for me to scan a modern car and the scanner directs me where the issue is). Thus i came to this forum to get advice. Unfortunately, in my local area there are not many shops that know how to fix these old cars. I live in Miami. They either deal with modern cars, work trucks, or those that do fix older cars ask for a blank check (i.e. i go in there with this, they will strip me naked and ask for 5-10k for repairs). It took me 7 months to get my dif repaired, because there is only one guy in the 100 mile radius, and even then, he fu*cked in up the first time, had to redo it, and i dont think he did it well again (and im out $2k). In another case I had a shop replace my fuel float, but they didn't bend it correctly (which from my understanding they really should have known this), so my fuel gauge is off (they refused to fix it, they just said old cars are like that). There are a lot of examples. Once i figure this out, the car is going for sale. I don't have any mechanics here and its an old car that i am unable to care for properly.
So again: I replaced the spark plugs (gapped at 0.45), I replaced the distributer cap, I replaced the rotor. All these were due to be replaced. I cleaned up inside the distributer with the electrical cleaner. I took off every wire sprayed electrical cleaner in there and ensured they fit nice and tight. I went for a drive, car was running better than ever at low rpm (before 2.5k) but rough at high rpm (3k and above) and was getting a lot of pops/backfire (never did that before. Spark gap was 0.35 on the old plugs, could the higher gap cause backfires). I went to adjust the timing (ive marked the original location), with the engine running, i turned it counter clock wise a little and went for a drive, car ran much worse at low rpm. I then adjusted it clockwise a littel (adjusting it a lot I would hear knocking, so i tried to adjust clockwise just enoguh so that i can't hear the knock). The car runs amazing at low rpm, as in i now have more power in low rpm than before the issue (feels like im up like 20-30hp). After 3k rpm it runs intermitten, i.e. not a clean pull in the rpm range. I do however have loose belts (they stretched and i have no more adjustment on them, i've ordered new belts). Could the loose belts cause poor performance after 3k rpm (they start to make a horrible squeel at 3k)? or am i still dealing with bad wires/distributer? Ill swap the belts when they come wednesday, to see if it improves. If not, ill order new spark plugs wires. If that doesnt' help, ill order a new distributer.
Am i right to assume:
A. it could be loose belts?
B. it could be that wires internally are just "gone" due to age (10yrs)?
C. Distributer is too far gone/internal problems?
Last edited:
euroz06
Well-Known Member
hmm. So it could have been that my spark plug wire came off the plug (due to a broken clip), i drove the car about 30 miles home with a missfire and that caused that spider web in the distributer cap? After replacing the distruber cap and rotor, the car drove better, but still had missfire. Misfire went away after i adjusted all the wires (including swapping 1 and 3), and sprayed that electrical cleaner everywhere. Now i have no missfire, but the car is not running smooth in the upper rpms.
I had a theory that maybe the car jumpend ignition somehow? i.e. there was a missfire, that caused the engine to jump ignition? but currently, at low rpm (under like 2.5k) it runs well (and i feel like i've added another 20-30hp), just at higher rpm it is not smooth and a lot of backfire (pops).
chewger
New Member
100% agree w/ 66 Sat. BTW, I just went thru a similar exercise on my Charger w a 400... I had a terrible backfire, then a miss or two. The wires didn't have that many miles on them, and the plugs even less. I was "sure" that wasn't the issue. I swapped the carb w/ a buddy's known good carb and that seemed to mostly fix the backfire, but not the terrible misses (and I still got a backfire or two when the timing wasn't set right). After a few evenings of head-scratching, I bit the bullet and bought a new cap, rotor, wires, and plugs, and wire separators (I already had a new ECU from a few months ago). Just to be sure, i took the time to do a compression check. Compression was consistent, so I moved ahead w/ the ignition part swaps. That's when I pulled out at least 1 plug that looked like it was dropped w/ almost no gap... and found oil on some of the wires where I couldn't see it from above. So much for being sure! I couldn't even get a consistent timing strobe off cylinder 1 before. After I got it all back together, I could... and I set the timing w/ a timing light... (-10 BTDC) BTW, I tried to replace one wire at a time to keep the order straight.... I still messed up once and ended up having to re-check the firing order 2 or 3 times. Now, the misses are all gone. Checking the firing order is easy, as someone has said... don't just swap wires. For Mopar big blocks, it's: 1-8-4-3-6-5-7-2, but don't take my word for it... check it online for your engine. Also, when you attach wires to the plugs and the cap, make sure you are getting that positive "click". Also, make sure your vacuum advance on the distributor is hooked up to the ported vacuum, not the manifold vacuum port. The ported vacuum changes w/ throttle, so it's easy to tell which is which if you put a finger on it while giving it throttle...
^^^^ agreed
padam
Well-Known Member
The wider gap will make it harder for a marginal ignition to fire the plug.
Geoff 2
Well-Known Member
Let's get rid of some of the BS. A plug gap of 0.045" & is NOT causing the problem. The plug gap recommendation from MSD for the 'box' igns is 050-060" for up to 10.5:1 CR.
[1] An obscure problem that can occur is the coil [-] wire is too close to the purple & green p/up wires. The high voltage on the coil [-] wire induces a voltage in the p/up wires that fires the ign at the wrong time.
[2] Keep dielectric grease AWAY from electrical terminals!!! It is an insulator & may prevent contact between contacts...that need to be in contact.
[3] If you have another dist, I would try it to eliminate a rotor phasing problem. If you have a Chrys elec ign dist: one p/up wire will be black. That connects to the MSD green wire. other p/up wire connects to purple. Use short leads with alligator leads to test or similar.
[4] Quite possible the 'box' or coil is faulty. The box can be bypassed [ & eliminated as a suspect ] by using a $25 4 pin HEI module to provide ign. Diagrams on the web.
[1] An obscure problem that can occur is the coil [-] wire is too close to the purple & green p/up wires. The high voltage on the coil [-] wire induces a voltage in the p/up wires that fires the ign at the wrong time.
[2] Keep dielectric grease AWAY from electrical terminals!!! It is an insulator & may prevent contact between contacts...that need to be in contact.
[3] If you have another dist, I would try it to eliminate a rotor phasing problem. If you have a Chrys elec ign dist: one p/up wire will be black. That connects to the MSD green wire. other p/up wire connects to purple. Use short leads with alligator leads to test or similar.
[4] Quite possible the 'box' or coil is faulty. The box can be bypassed [ & eliminated as a suspect ] by using a $25 4 pin HEI module to provide ign. Diagrams on the web.
padam
Well-Known Member
So you don’t think that a wider plug gap can contribute to a misfire when plug wires may be in bad shape?
euroz06
Well-Known Member
So I replaced the coil in one of the earlier steps (car seemed to have ran better, but was still misfiring). I think the old coil was out the door. Ill double check that the wires are positioned well on the coil. I do want to highlight, the original misfire is gone. Car runs great in low rpm. I now have an issue at high rpm's, its not smooth and lots of pops/backfire.
I can describe the amount of backfire this way: i have electrical cut outs (after 3 inch headers), and on rare occasions ill open them up and the car would do very cool pops and bangs, but once closed there were no pops. Now, im getting similar pops with the cut outs closed via my regular mufflers (also should mention that the muffler cans are new, i.e. my orignial ones rusted out... so maaaaaybe i just didn't drive the car hard with them on and didn't notice the pops with new muffler cans? maybe i fixed up the system a bit and its supposed to be like this?). I mean, tt sounds cool and all, but I just dont know what is normal for the car. I did have a 73 charger before, with a built 440 and supertrap exhaust, and that thing would pop about the same, but im pretty sure it was supposed to do that with that exhaust.
Hmm, i did originally use a lot of dialectic grease on the spark plug wire (to get the rubber boot onto the plug, as it was impossible without the grease), I then tried to remove some of it, but there still might be grease inside the rubber boot where the wire connects to the plug. Ill get some q tips to get in there to clean it up better. Thank you for this! I looked on youtube how to fix the plug and they used the grease. Ive only used the grease on the plug wire for 3cyl (now on cyl 1). I might also have to go clean those plugs, as some of that grease might have ended up on the plug...
- Separately, when i was describing the later steps, ive used QD electronics cleaner, which i dont believe leaves resedue (spraying the other plug wires, inside the distributer, etc).
chewger
New Member
What you are now describing is presenting as a backfire through the exhaust.... it may still be a miss, but could be other things. I would check 2 things...
1) As I posted above, I'd check the distributor vacuum line... a leak here or if it's not hooked up to the correct ported vacuum line could cause those symptoms. I'll stop short of saying you should check your distributor advance since you say it was running fine before, but I'm curious if others think this could be something to check/clean/lubricate.
2) Check carburetor mixture screws to make sure you're not running too lean... perhaps run a little too rich as a test. A vacuum leak elsewhere could also cause this.
Finally, if it were me, I'd bite the bullet and get new wires just to eliminate that as a possibility. If it doesn't, you now have your extra set of wires to help debug an issue down the road.
1) As I posted above, I'd check the distributor vacuum line... a leak here or if it's not hooked up to the correct ported vacuum line could cause those symptoms. I'll stop short of saying you should check your distributor advance since you say it was running fine before, but I'm curious if others think this could be something to check/clean/lubricate.
2) Check carburetor mixture screws to make sure you're not running too lean... perhaps run a little too rich as a test. A vacuum leak elsewhere could also cause this.
Finally, if it were me, I'd bite the bullet and get new wires just to eliminate that as a possibility. If it doesn't, you now have your extra set of wires to help debug an issue down the road.
padam
Well-Known Member
Header/exhaust manifold leaks can sound like a misfire or mechanical tap , and will cause backfire through the exhaust on deceleration.
You really have to isolate the malfunction. First step of troubleshooting.
You really have to isolate the malfunction. First step of troubleshooting.
euroz06
Well-Known Member
ill take a look at the vacuume lines, thank you. So it is possible its carb related? i have been looking at it thinking maybe it needs to be rebuilt? About a year ago I replaced the fuel lines going to it, I've also had the float get stuck around the same time (i.e. it wasn't idling well, so i've used a plastic hammer to knock at the back chamber, and the car started to run better). I do use carb cleaner now and then
padam
Well-Known Member
Diagnosis is what you need. Read up on how to test the various systems. Right now you are just grasping at straws.
TN Mopar
Well-Known Member
It's time to back up and Punt
your inexperience has made it difficult to diagnose and possibly made the problem worse
It's okay, that's how we learn, but now you need to establish a base line before you can move forward
This car needs a full tune up
It's been 10 years, it's due
New Cap, New Rotor, New Wires, New plugs (yes I see some of this has happened)
install all of the parts with Factory Specs exactly as the factory says
Set your timing with a timing light, don't guess and don't just move the distributor until it feels right
Now you have your baseline
Drive it, is it still missing?
After you solve the miss you can fine tune the tune
Some of your questions are basic
I personally don't like .045 gap but I use .40 with my MSD ignition
your carb can be an issue
your engine pops when you open the cutouts because it leans the engine
My car slows at the track when I open my cutouts unless I enrich it to account for the lean condition
vacuum leaks and or coils going bad can cause it
(even MSD coils go bad)
TLDR
Full tune up time
Set a base line and start over
your inexperience has made it difficult to diagnose and possibly made the problem worse
It's okay, that's how we learn, but now you need to establish a base line before you can move forward
This car needs a full tune up
It's been 10 years, it's due
New Cap, New Rotor, New Wires, New plugs (yes I see some of this has happened)
install all of the parts with Factory Specs exactly as the factory says
Set your timing with a timing light, don't guess and don't just move the distributor until it feels right
Now you have your baseline
Drive it, is it still missing?
After you solve the miss you can fine tune the tune
Some of your questions are basic
I personally don't like .045 gap but I use .40 with my MSD ignition
your carb can be an issue
your engine pops when you open the cutouts because it leans the engine
My car slows at the track when I open my cutouts unless I enrich it to account for the lean condition
vacuum leaks and or coils going bad can cause it
(even MSD coils go bad)
TLDR
Full tune up time
Set a base line and start over
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