Trouble with my 1996 Grand Caravan

[munchies]

1996 Dodge Caravan 6 cyl Two Wheel Drive Automatic 115000 miles

My Service Engine Soon light in my 1996 Grand Caravan is blinking, and the car is running really rough. It doesn't accelerate very well, and shakes rather violently when it does. It also shakes when idling.

I took to to a local auto parts store and they hooked up a meter thing that first told me I was getting a random misfire (code P0300 I think), then it said spark plug 4 was misfiring. My husband replaced all the spark plugs and wires except for one that he can't figure out how to get to.

Still running rough, engine light still on. I took it back to the auto parts store and they hooked the meter up again and it said random misfire again without specifically naming a plug, and also said we needed to replace the Output Speed Sensor, so we did that.

Car is still running rough, so I took it back today and I'm still getting the random misfire code. Is it likely that it's that last plug and my husband just needs to figure out how to get to it? Or is there something else we should be looking at too?

Thanks!

[mfahey]

First of all, with the SEL blinking, that is a sign of impending doom for your catalytic converter if you continue to drive it. You didn't mention which plug he is having trouble with but assuming it is a rear one, many people say that on this vintage van, the easiest way is to remove the wiper tub. Here is a link that should help: http://www.dodgetalk.com/forums/showthread.php?t=155612&highlight=wiper+tub

[munchies]

So I need to stop driving it? I've only been taking it to the auto parts place, which is less than 3 miles away. I do not want anything else to break though.

I think he said it was the rear passenger side, and he took off the top half of the engine (I don't know what the means, but I think that's what he said). I'll print out that link you gave me and hopefully it's that one so he can get it all done.

Thanks so much for the reply!

[munchies]

He says it's the middle plug and that my windshield wiper tub is on the left side and not near the one he can't get to. He says he's sure it's number 3 that he can't reach.

[Rick99]

If you have a random misfire, you should be looking for problems that affect all of the cylinders-- not just one spark plug. It's also unlikely that all of the plugs and wires would go at once, so although changing them won't hurt, it's probably not addressing the problem. I'm not so familiar with the older vans, does this have a distributor or does it have a coil pack? (Hopefully your husband will know if you don't.)

Make sure your battery is in good shape (a shorted cell or corroded terminals can wreak havoc as computers, etc don't get the voltage they need)

Check fuel pressure (low pressure could be caused by a bad pump or clogged filter.)

Check for air/vacuum leaks (vacuum hoses disconnected or damaged, air leaks at intake manifold gasket)

A compression test might be a good idea just to cover basics.

It would be interesting to know what your fuel trim is doing if the parts store scanner can tell you that (probably not).

[munchies]

Argh! Still dealing with this, we've changed all the plugs, all the wires, the output speed sensor, and the coil pack.

Our neighbor came out to help and between him and my husband they cannot figure this out.

They checked everything they could think of, my husband is at work but I'll update later with everything that they did.

The spark plug is not getting a spark. The neighbor thinks that maybe the computer isn't telling the plug to fire. He said that's an expensive part to fix, and I'm hesitant to try that route without consulting a professional either.

This is really frustrating, and I don't know what else to do. I'm worried about taking it in, because we don't know any mechanics so we don't have anyone that we trust and I'm worried about getting ripped off.

I'm so stressed out. If anyone has any ideas, I would really appreciate it.

[1997caravan]

Been lurking on this site for a while(since I got a 97 caravan) but haven't posted much so "they" won't let me post a link.Spark is not the only thing missing to cause a misfire-fuel problems or air (vacuume leaks) will cause this code.Go to Google,type in engine misfire,about the third result down is a website called random misfire-you will find this very helpful. Good Luck!

[vabear]

Do the key dance (key on, key off, key on, key off, key on and wait) the CEL will start to flash the codes (example, one flash, a pause, two flashes, a pause is code 12) when she gets to code 55 (end of test) you will have the codes and go to the OBD codes on this forum and see what you have. Then post for us or get the readout from your parts place and post.

[Madbradthe2nd]

I was gonna say I don't know if it has a coil pack or distributor but it looks like you have changed the coil pack. Is that a coil pack for 6 cylindars or 3 coil packs for 2 each? You can test the coil packs on a bench with a simple ohm meter.

I also considered the possibility that the PCM is not telling one of the packs to spark, but it doesn't necessarily mean the PCM is bad. It probably means the PCM knows about a problem such as a loss of vacuum somewhere or some sensor out of range or whatever and is altering commands accordingly. However a more likely scene is a bad wire supplying a coil pack, assuming all the packs are good and connected properly, as are the wires and plugs.

The owner's manual for your vehicle clearly states that a flashing CEL is more serious than a constant CEL and service must be sought immediately, and the vehicle should not be driven. Among other dangers, unburnt fuel will destroy the Catalytic converter as already mentioned.

[mfahey]

If memory serves, someone else on here had a similar problem and after trying about everything, found that the wire from the PCM to the injector had been munched on by a rodent. So that's a possibility as is a bad PCM. Checking the wiring harness is free so I'd try that first.

[1997caravan]

If an injector was not working I don't think you would have a random missfire- the po code would point to a specific cylinder-right?

[Madbradthe2nd]

yeah misfire refers to spark; Fuel is a separate thing altogether.

[mfahey]

yeah misfire refers to spark; Fuel is a separate thing altogether.

I'm not sure that's entirely correct. My understanding is that the computer monitors the crank sensor and expects to see a certain amount of movement when a particular cylinder fires. If that doesn't occur, it says it there is a misfire with that cylinder. Things that could cause this are the obvious electrical issues but also a bad valve, clogged injector or anything else that would prevent that cylinder from developing the power that the computer expects to see.
Random misfire could be caused by fuel delivery issues because it would affect multiple cylinders.
Someone can correct me if I'm wrong but that's my understanding.

[1997caravan]

yeah misfire refers to spark; Fuel is a separate thing altogether.

I believe this is completely incorrect! Anything that causes the cylinder to not have combustion will log a misfire code- fuel pump,clogged filter,vacuum leak in intake manifold,throttle body,vacuum plumbing,EGR valve leaking exhaust gas into intake manifold as well as all spark related parts will cause a random misfire- but if the code is limited to a specific cylinder then that limits the possibilites down quite a bit! Typically to plug, wire, coil,injector and wiring.

[Madbradthe2nd]

I stand corrected I thought it merely monitored the spark to test for that. I figured it monitored injector activity to report on fuel/injector, like it could probably tell you something about injector wiring if an injector is unplugged. Explain about cylinder movement - The piston moves regardless of whether it got an explosion simply by virtue of being connected to the crank. The crank sensor is sensing the crank is turning, and it's turning - there are 5 other working cylinders. Does the crank sensor not also have the job of detecting the crank's position for other purposes, in the way that the cam position sensor does?

[1997caravan]

Just checked the service manual and it says misfires are detected by crank position sensor.An rpm value is set for each cylinder and if there is a difference of more than 10RPM a misfire count of 1 is recorded.They call it Crank speed fluctuation method(CSF)
Amazing, they can tell a 10RPM difference between cylinders!