2001 Dodge Caravan misfire. Unevevn spark.

Tiny
SH4664
  • MEMBER
  • 2001 DODGE CARAVAN
  • 200,000 MILES
3.3l engine is misfiring on multiple cylinders. Getting what seems like a weak spark on 1, 3, and 6. Get little white sparks only when keeping the wire really close to the spark plug. On other cylinders the spark is arcs quite strong, blue and orange in color. I have changed coil and wires, spark plug look good but reguaged and reinstalled. I can hear injectors clicking using stethoscope. There are no engine codes. Not sure what do to next.
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Saturday, September 28th, 2013 AT 11:23 AM

19 Replies

Tiny
SH4664
  • MEMBER
Correction to the message posted. On 2 4 and 5, the spark is bright white and arc goes circularly when holding the wire close to the spark plug
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Saturday, September 28th, 2013 AT 11:40 AM
Tiny
HMAC300
  • EXPERT
Check to see if the boots are cracked or broken as it goes circularly. Then check cransk sensor for resistance and connection. Check fuses under hood as well.
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Saturday, September 28th, 2013 AT 11:48 AM
Tiny
SH4664
  • MEMBER
I changed the wires and was getting the same result so I am thinking boots are ok but will double check again.

What resistance should I see on crank sensor, and are there any particular fuses I should be checking.
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Saturday, September 28th, 2013 AT 11:53 AM
Tiny
HMAC300
  • EXPERT
Just ecm ign fuse s if there are any. And we have no figures on crank sensor. Are you sure you aren' teven getting a P0300 code auto parts do that fro free. Also check for vacuum hoses off or any grommet on valve covers or air duct leaks.
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Saturday, September 28th, 2013 AT 11:59 AM
Tiny
SH4664
  • MEMBER
100% no cylinder misfire codes. Drove 30 miles hoping it would set some code but it didn't. It had set a large evap leak code a few months ago but the car ran fine and after resetting that code, it hasn't come back since. The misfire started couple of months after that.

When I say arcs are going circular, its not when boots are on the plug (that would be cracked boots), its when I removed the boots and held close to the spark plug to see if I was getting spark (others might hold it close to the engine block), and that's when on the 3 cylinders spark flew arcing across the engine bore around the plugs in a circular motion. On the other three cylinders the arcs are really small flying from wire to the tip of the spark plug.

Anyway checking your recommendations now
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Saturday, September 28th, 2013 AT 12:16 PM
Tiny
SH4664
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There is a fuse labeld ign which is good.

If there are no figures for crankshaft resistance then how do I know if my readings are for good or bad sensor.
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Saturday, September 28th, 2013 AT 3:26 PM
Tiny
HMAC300
  • EXPERT
Check against a new one at auto parts. I don't know if I said or not but check for a vacuum leak as well with choke cleaner and look for hoses rotted split holes etc.
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Saturday, September 28th, 2013 AT 3:28 PM
Tiny
SH4664
  • MEMBER
You had mentioned vacuum leak and I don't see any. Why would vacuum leak cause unevevn spark. I can understand erratic idling but not weak spark
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Saturday, September 28th, 2013 AT 3:35 PM
Tiny
HMAC300
  • EXPERT
Misfires are extremely hard to diagnose even for a pro so you have to eleimnate everything first. Because to a pro it may seem ok about the spark you are talking about.
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Saturday, September 28th, 2013 AT 3:36 PM
Tiny
SH4664
  • MEMBER
Thanks. Would large evap leak code that I mentioned before might be causing this even though it hasn't come back again
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Saturday, September 28th, 2013 AT 3:39 PM
Tiny
HMAC300
  • EXPERT
Yes I have no further suggestions without doing tests myself.
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Saturday, September 28th, 2013 AT 3:42 PM
Tiny
MADMIKE1735
  • EXPERT
The coil you replaced with, was it a dealer coil, or aftermarket? Ive seen new coils that were bad out of the box. Your complaint is weak spark on some, good on others. Verify its good out of coil 1st. Take a known good wire, and connect an inline spark tester (one that u can adjust the gap on) so u can check for a healthy blue spark. If still no good spark, we will need to further diag.
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Tuesday, October 1st, 2013 AT 3:43 PM
Tiny
MADMIKE1735
  • EXPERT
Ive been stewing on this for a while. You said you drove it for a while, and still no check engine light? If you dont have spark, it would set a flashing CEL for whatever cylinder is misfiring (it flashes because its performing damage) the firing order on this, are you certain its correct? You may have crossed wires, so it runs, but wont set a misfire code.
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Tuesday, October 1st, 2013 AT 7:14 PM
Tiny
SH4664
  • MEMBER
Thank you for the follow up madmike1735.

I had replaced the original coil pack with an aftermarket couple of years ago as a "routine maintenance". The original coil was working fine so I had kept it as spare. When misfire started, I first swaped with the original coil that I had kept and then got another brand new one. Both swaps didn't fix the problem.

Regarding spark check, I used an inline spark tester that flashes and things looked ok. I then decided to do an alternate check by pulling the wires and holding them close to the spark plug tip. My plugs sit between exhaust manifold and what I noticed was that bright white sparks arced to the manifold in a circulation on each fire on cylinder 2 4 and 5. On the other three cylinders I saw small bright white arc going between wire and spark plug tip. When I turned the a/c on (this is when misfire is most obvious) and reved the engine, sparks on 1 and 6 disappeared. I didn't check 3, but I think its safe to say that it lost the spark. As well.

I have checked and rechecked for cross wiring. My wires and coil have numbers on them so its difficult to make mistake.

I was considering replacing crankshaft position sensor but something tells me that's not the problem. Mostly when crank sensor fails, there is no spark on all cylinders.

The van shudders badly over 40; you can't drive the thing so I am baffled why its not setting at least some code.
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Wednesday, October 2nd, 2013 AT 1:11 PM
Tiny
MADMIKE1735
  • EXPERT
Yea, the crank sensor will cause a loss of spark to all cylinders. An inline spark tester will give false readings- as you found out by checking for a healthy spark by pulling wires, and checking for the spark to jump. Im confused as all hell on this. Your coil takes voltage it recieves, and through "coiling" very fine wire inside, it amplifies your voltage, and thats why you get a good spark. Its increasing for example a 12v signal, but multiplies it to an output of maybe 20,000 volts. (Some cars go up to 60,000 volts) what bothers me, is your coil is giving the symptom of not working. Its getting a signal to it, but not multiplying it for say, and is giving a lousy spark on 1, 3, and 5 cylinders. Is this making sense?
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Friday, October 4th, 2013 AT 4:39 PM
Tiny
SH4664
  • MEMBER
It makes sense but I don't know where to go from here and what to eliminate besides throwing parts.
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Friday, October 4th, 2013 AT 5:10 PM
Tiny
MADMIKE1735
  • EXPERT
Id hate to see you waste money, and time also. But the evidence here is pointing towards the coil. I hate aftermarket coils (been burned by them-new out of box, and no good) I would buy a new coil from the dealer. I know its not the answer your looking for, but we need to eliminate it. I understand you have the one that came out. But coils do break down over time. Start with a new one. Or if you know anybody with the same vehicle- see if you can borrow their coil just to verify it will correct the problem. Coils are most common, and my gut is saying go with it.
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Friday, October 4th, 2013 AT 5:25 PM
Tiny
SH4664
  • MEMBER
Wanted to post the find for others. The coil wasn't the problem. In the end, it turned out to be a bad spark plug. Still don't know why no misfire code was being set but then I am no expert on how the computer system works.

Thanks Madmike1735 for trying.
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Monday, November 25th, 2013 AT 4:40 PM
Tiny
MADMIKE1735
  • EXPERT
Im very glad you found the problem! Give your self a pat on the back, you earned it! Wierd a single plug caused this. Usually it will set a misfire code fast. Without access to a good scan tool, we couldnt have told you to gain access to Mode $6. This is the easiest way to verify a misfire in a cylinder. However these scan tools cost atleast 2500$ (thats what I paid for my OTC genisys)
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Tuesday, November 26th, 2013 AT 3:55 PM

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