98 Dodge Grand Caravan misfire

Tiny
DNSTILKE
  • MEMBER
  • 1998 DODGE CARAVAN
My 98 Dodge Grand Caravan has been acting up, missing and back firing. I took it in and had it put on a computer, the results came back misfire on #3 cylinder. So I changed all the spark plugs and plug wires. The problem was not fixed. My brother in law said that the same thing happened to his parents van and it was something in the computer sending the wrong signals to the engine. Any ideas?
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Tuesday, November 13th, 2007 AT 11:14 PM

6 Replies

Tiny
JACK42
  • MEMBER
More likely a bad injector. First do compression test to be sure it is ok. Then, since the plugs are new, remove #3 and any other and compare the color. Does that engine have just one coil?
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Wednesday, November 14th, 2007 AT 7:53 AM
Tiny
DNSTILKE
  • MEMBER
To be honest I am not sure how many coils there are. The engine is a 3.8L if that is any help. The #3 spark plug is the back middle one and they are impossible to get to without having to remove part of the engine so taking it out is not really an option.
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Wednesday, November 14th, 2007 AT 1:05 PM
Tiny
JACK42
  • MEMBER
If you arent willing to remove the plug and check it, then im not sure how much help I can be to you. You wouldnt believe some of the things that have to be done to get access to areas, but it helps make a more accurate diagnosis.
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Thursday, November 15th, 2007 AT 7:55 AM
Tiny
DNSTILKE
  • MEMBER
I guess if that is the only way, I will look into having it done. The thing is I just paid someone (a professional) to put the spark plugs in a week ago. I had to problem before and after the plugs and wires were replaced. And it has only been a week since I did that.
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Thursday, November 15th, 2007 AT 9:28 AM
Tiny
DENNIS MCLINN
  • MEMBER
Your main power wire has a bad connection on the dash cluster, you can google the repair. Fixed mine in a afternoon.
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Wednesday, February 22nd, 2017 AT 11:42 AM
Tiny
CARADIODOC
  • EXPERT
If I may add a few tidbits of information, forget the injectors. Chrysler buys their injectors from Bosch in flow-matched sets, and has extremely little trouble with them. Since 1990, I've read about one bad one. If you were to suspect a bad injector or spark plug, swap that one with one from a different cylinder. Erase the fault code, then see if a code sets for the cylinder you moved the suspect part to.

When you have a running problem, you need to list the engine size right away. There can be four or five, and some of them have wildly different ignition systems from the others. You also need to list the mileage and transmission type. We make generalizations based on that when deciding the order of things to check. It's not fair to make us guess, or to waste time dragging that top secret information out.

You're right that number 3 is the rear, center cylinder. It is easy to get to from underneath when the van is on a hoist. If you try to do it from the top, the long black bucket holding the wiper system can be removed to improve access.

The 3.8L uses three ignition coils in a coil pack, or assembly. The easiest is to get a good used one from a salvage yard to try as a test. While it's not real common, a partially-shorted coil can fail to develop sufficient voltage to fire the pair of spark plugs under all conditions. What you hear as a backfire could be the unburned fuel from a misfire going into the exhaust system where it fires and creates the sound of a backfire.

A deteriorated spark plug wire can cause the same symptom as a weak coil. A better suspect is a failing crankshaft position sensor or one that was installed improperly without the spacer needed to set its critical air gap. If the history of that sensor is unknown, your mechanic can use a scanner with graphing capabilities to record the sensor's signal while the problem occurs. If you see the signal pulses drop out completely, intermittently, suspect the sensor is failing. If you see the signal voltage drop just a little, but it's enough for the computer to be unable to read it, resulting in a momentary misfire, suspect the air gap is too big.

You don't have to run to your mechanic to have diagnostic fault codes read. Chrysler makes doing that yourself much easier than any other manufacturer. Cycle the ignition switch from "off" to "run" three times within five seconds, without cranking the engine, leave it in "run", then watch the code numbers appear in the odometer display. You may only get a code indicating which cylinder is misfiring, but if you're lucky, one will set related to the crankshaft position sensor. Remember that fault codes never say to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a part is referenced in a fault code, it is actually the cause of that code about half of the time. First we rule out wiring and connector terminal problems, and mechanical problems associated with that system.

Also be aware a lot of people, including some mechanics, still believe there is no fault code to be read if the Check Engine light isn't on. That is absolutely not true. There can be over 2,000 potential problems detected. About half of them refer to something that could adversely affect emissions. Those are the codes that turn on the Check Engine light. A fault code related to a crankshaft position sensor or camshaft position sensor will usually not turn on the Check Engine light. That is because with a totally-failed sensor, the engine won't run, and a non-running engine can't create excessive emissions.
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Wednesday, February 22nd, 2017 AT 3:27 PM

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