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I have a 02 dodge caravan 3.3 flex. My problem started out as a miss every once in a while. Now it has progressed to I believe multiple cyclinder misfiring. It stumbles upon acceleration. Changed plus. They were very bad. Found out they had 103,000 miles on them. Wires seem ok. Checked foil pack as per manual. Checked ok. I have noticed that there is no way for me to check timing. Can the coil pack fail when heated up? Trying to figure out what else to check.
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No I have not checked those yet. I will have to rent one. Here is what I have done so far. I was thinking water in bottom of tank so. I put some e 85 in it. Drove fine. Then a couple of pops through throttle body and straightened out. Parked in drive way and at idle it’s ok but when you rev it up it will start popping through throttle body.
Coils can fail intermittently and can also be temperature dependent. It would be good to check codes if you can. Early on in that generation, the fuel injector harness was prone to melting and shorting out on itself. It wasn’t very well protected from the heat coming off the exhaust pipe that crosses over between the exhaust manifolds. Look at the left end of the of the engine behind the upper intake and it’s usually pretty obvious if there is a melt down.
At this time the only code is a small very small leak in evaporate system. I checked secondary resistance on coil it shows 12,300 ohms. Thinking that is low considering they say 10,000 – 19,000 ohms. Checked plug for injector harness seems good but will check wires more closely. Is there a range for degree for timing. Was looking a code reader say ignition timing 45 degrees but that wa at like almost 3,000 rpm’s. Can timing be an issue. Van has 207,0000 not sure when it was it was changed or if it has ever been changed. Still has power just small popping through throttlebody
It shouldn’t be a timing problem. I’ve seen the flex plate crack around the mounting bolts an the entire plate shifted forward throwing off the crank signal timing, but that affected the engine as a whole so no one cylinder was causing a misfire or a backfire. If you’ve got a vacuum gauge, throw it onto a vacuum port and see what it’s telling you. I’d assume that it’s going to show a vacuum of 19-21″ with negative spikes in vacuum.
Since you seem to be suggesting the backfire can have an on again/off again quality to it, I’d stick with misfire diagnosis of the coil pack or injectors for now. Unfortunately, you don’t have much to access to disable cylinders though for a power contribution test. My method might scare some, but it’s all I can offer. I have jumper wires with alligator clips attached to them. I’ll attach one clip to a long handle screwdriver and the other to a clean ground on the block or transmission. Never go directly to battery ground for this test. With the engine running, leave the screwdriver tip close to a coil terminal as you pull the plug wire off. If that cylinder is firing normally, the engine will run worse with pulling the plug wire. A dead cylinder wont cause a change in idle characteristics. As you’re pulling the wires off at the coil, watch for spark from the coil to the screwdriver tip. And always make sure that the tip stays nearby each coil terminal so the spark has some place to go. If you don’t keep that screwdriver wired to a good ground, you get a jolt or 12 for the effort.
Start there if you like, and keep reporting as you learn stuff.
I have been messing around with this van for a while. Check fuel pressure. Pressure ok. Have not checked coil pack or try to see which cylinder is missing. But to add to the confusion of all this. being a flex fuel vehicle I ran 1 tank of e85 in it. When that tank got to 1/8 tank started to run bad gain. Put regular gas in it and started running good again. Thinking something in bottom of tank. When you go up an incline or try to go into passing gear I hear 3 pops and it will then go. A friend at work said he heard my van making a noise but sounded like a metallic sound popping sound. Can the axle or wheel bearing make this sound only under load? He said it almost like the axle is slipping. Not sure where else to look.
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