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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / October 20052000 Caravan Missing
This morning I got in my wife's 2000 Dodge Caravan (2.4l 4cyl). It's been running fine. Well, it ran REAL rough, like a cylinder was misfiring. The check engine light came on then started blinking. I took it to Autozone and they put the computer analysis on it. It said it was a misfire in cylinder 2. This made sense since it has 90,000m on it and the plugs were never changed. I changed the plugs, and wires. It's better now, and the check engine went off (after disconnect and reconnect of the battery), but it's still running very rough, seemingly still missing, though not as bad. Any ideas what else the problem might be. I realized after the fact that I didn't gap the plugs. Could this cause the problem? Someone suggested the ignition coil or module, but I don't want to drop the $$$ for that unless I know that's what it is. Thanks >This morning I got in my wife's 2000 Dodge Caravan (2.4l 4cyl). It's >been running fine. Well, it ran REAL rough, like a cylinder was [quoted text clipped - 16 lines] > >Thanks Hey I'm only a shade-tree wannabe...nevertheless, you need to have spark air/fuel mix correct timing of valves relative to piston position So out of those, since you didn't gap the plug, go back and do that now. Then you have eliminated that possibility. You can even by a device you can put in-line with the plug, I don't remember the name of it, that will flash when the wire is *hot.* Then you know, and that is how you fix things. Not by guessing, but by =measuring=. Next, it could be trouble with the fuel injector for cylinder 2. You can actually listen to it with a stereoscope you can buy at an auto parts place. Listen to injector for cyl #2, and then compare the sound, frequency to the other 3 injectors. Does it sound the same or different? If it is different, it could be that the signal to it is incorrect, you would have to put a scope on it to see the waveform to determine duration and amplitude. It is like a garden nozzle squirting gasoline. It opens for a set period of time, and then closes. If this is not opening because of poor electrical signal, then you have to do the electrical troubleshooting. Or, the signal to it might be perfect, but it might be sticking ( gooey ). Mechanical problem there then, possibly to be solved with a tank of gas mixed with Techron Fuel System Cleaner, NOT the Techron Fuel Injector Cleaner, which is basically the same stuff but more diluted. This is enough now to get you started. Check back. Maybe a real *expert* will chime in with the Magic Answer we're all waiting for. Lg > This morning I got in my wife's 2000 Dodge Caravan (2.4l 4cyl). It's > been running fine. Well, it ran REAL rough, like a cylinder was [quoted text clipped - 16 lines] > > Thanks Gap the plugs.... it will help, but they are usually gapped pretty good when you buy them. The other thing I might suggest is this: Inspect the distributor cap and air filter as well, and if they look beat (chances are if you haven't changed the plugs, you haven't done anything else either) change them both.... after changing them, you basically have done a tune up.... almost complete, but enough to make a huge difference. Or, if it doesn't cost anything for them to analyze it, take it back to Autozone and let them analyze the van again. Tell them it still runs rough, and see what they suggest to replace.. there may be things like an oxygen sensor which could cost some money.... Good Luck.. Fwed Thanks for the ideas. It's not got a normal distributor with a cap. It's an electronic type, that's square. I think it's called the coil. It's 90 bucks though so I don't want to guess. I'll try the gapping and the fuel system cleaner. I checked the ignition coil between cyls 2-3 and got 13.4k ohms and 13.6k between 1-4. According to the manual it should have been 3.2 and 4.2k ohms respectively. However there is an electrical connector that I believe I'm supossed to remove before the test but I haven't been able to do so. I also changed the air filter, oil and filter, gapped the plugs. I don't know if it's an injector problem, or firing problem. How can I tell? >I checked the ignition coil between cyls 2-3 and got 13.4k ohms and >13.6k between 1-4. According to the manual it should have been 3.2 and [quoted text clipped - 6 lines] >I don't know if it's an injector problem, or firing problem. How can I >tell? If you are daring ( and _careful_ ) you can pull the plug+wire and set them on the valve cover somewhere. Turn over the engine for a few seconds and you should see a nice SPARK at the plug gap. Then....you know it is =working=. At that point, you have eliminated the ignition system as a/the problem and now know it is fuel-related ( injector? ). Re-install plug + wire being very careful about not bending the wire ( the conductors break easily ). Lg I had read about that elsewhere. But the plug wire has the conducter on the plug side recessed about 2 inches inside the rubber boot. The boot doesn't seem to want to pull back off the connector. Can I just hold the plug wire with rubber covered handles? Thanks >I had read about that elsewhere. But the plug wire has the conducter >on the plug side recessed about 2 inches inside the rubber boot. The [quoted text clipped - 3 lines] > >Thanks No, do not attempt to hold the plug wire with anything. There is too much voltage there. You might not kill yourself but you could end up with a very memorable and unhappy experience if the hi voltage decides you are the path of least resistance to ground. IOW, no. The boot doesn't want to come off the plug. Then, they sell a boot removal tool for a couple of dollars at Pep Boys. Twist and pull and it will come off the plug. Then, reattach once the plug is out of the plug well. The idea, is to watch the plug fire. You can't really see this happening when it is screwed into the block. ;-) You just want to rest the plug on some metal of the engine block, because that is ground. The center conductor of course is high voltage B+. There is your circuit. No, Dolf, you don't want to be touching _anything_ when you do this kind of test. Have both hands in your _pockets_. You only need to run this test for a few seconds...long enough to see the spark jump the gap from the center electrode of the plug to the base electrode that comes off the threaded body of the plug. If you see a spark there consistently, then your ignition to that cylinder isn't the problem. Keep Safe. Safety is No Accident. Hi Voltage of the kind coming from the coil pack isn't going to do your heart any good if you get bitten. Lg > I had read about that elsewhere. But the plug wire has the conducter > on the plug side recessed about 2 inches inside the rubber boot. The [quoted text clipped - 3 lines] > > Thanks For safety's sake it's always best to disable the injectors and fuel pump during a cranking spark test. It's easy enough to remove the four injector connectors temporarily. You can also pull the fuel pump relay if it is accessible. Then just remove the plug from the test cylinder and put the plug in that cylinder's wire boot. Rest the threaded area of the plug on bare engine metal and crank. Look for a sharp, blue spark. Know that a compression sound will come from the cylinder without it's plug when you are cranking. You can avoid removing the in-use plug if you have a spare plug lying around -or- a spark tester (~$10). Toyota MDT in MO Thanks everyone for all the help. Removing the spark (I was trying to do it edmechanics way, that was the confusion about the boot. Anyway, I get spark on 1 3 and 4 cyls, but not the 2 cyl. The original computer diagnostic code was "misfire on cyl 2". I'm not sure why the engine light went away, but it appears that is definately still the problem. Ok, it's Electronic Ignition of course. So, there's no cap like I was used to. Where the cap normally is, is a square unit with the 4 wire plugs on it. Is this what's called the coil? Is this what I should change? Note: new plugs and wires, now properly gapped. >Thanks everyone for all the help. Removing the spark (I was trying to >do it edmechanics way, that was the confusion about the boot. [quoted text clipped - 8 lines] > >Note: new plugs and wires, now properly gapped. Some people call it the *ignition module.* Who knows what they call it in your car. Hey, nice job. No spark, then the IM is kaput. Congrats! You've saved yourself $$$. Lg > >Thanks everyone for all the help. Removing the spark (I was trying to > >do it edmechanics way, that was the confusion about the boot. [quoted text clipped - 10 lines] > > Some people call it the *ignition module.* And they'd be wrong. This particular Chrysler vehicle doesn't have an ignition module per se. > Who knows what they call > it in your car. "Coil Pack." > Hey, nice job. No spark, then the IM is kaput. Congrats! You've > saved yourself $$$. No where near enough diagnostics yet to throw a party. No spark on #2, yet there is spark on #3 which is the same secondary winding. An ohmmeter check of the coil secondary and coil primary is in order. The way I check for spark is to pull the wire off the plug and put a phillips screwdriver in the boot and hold the shaft close to metal on the engine while holding the plastic handle. but short of doing this (i've been shocked lots of time), might be bad for someone's heart but I ain't dead yet. I would get a spark tester because that little gap of the spark plug takes a certain amount of voltage to jump, the bigger the gap the higher the voltage the coil needs to produce but also the high compression in a working cylinder causes a higher voltage to be required. So if the coil jumps a spark plug gap in plain outside air, it might not make it when the spark plug is screwed into the engine. So for air you need at least 1/2 inch spark gap up to at least 3/4 inch or more in an HEI system. If you take out spark plug with regular gap and lay on engine with wire attached and it jumps it, Ive been fooled by that before. You need to get a spark tester and adjust gap to at least 1/2 inch and see if it jumps that.
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