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Discussion Starter #1 (Edited)
ok. i have been doing my own work on my vehicles for years so I now enough to get by. so here is my issue. This is the first time it has went down.

I have a 2002 dodge grand caravan sport 3.3L 204,000 miles, and bought the dealer service repair Manuel (not Haynes manuals either) it start stumbling and threw codes P0300 and p0301. P0300 is a misfire affecting all cylinders and is random, p0301 is cylinder one specific. WE ALL KNOW FUEL FIRE AND AIR so below is the short and sweet version along with the history of the problem. I cant type the whole story.because i dont have enough room.

((((((((SHORT AND SWEET)))))))
I have new fuel filter and good fuel pressure (FUEL PSI WAS 58ish)and good working unclogged injectors with no electrical shorts and I have proper resistance and continuity from the injectors to the PCM. I have a new coil pack, plugs and wires, and I have proper resistance and continuity from the coil to the PCM. I have no vac leaks along with good compression, a new IAC, new EGR value and new upper and lower intake gaskets/seals and new throttle body gasket and seals. Why do I have a rough ideal? vacuum was 24 in-lbs, compression was 130ish
test preformed: fuel pressure test, vaccum leak tests, compression test, resistenace test, continuity test

(((((((HISTORY))))
FUEL:::: I tested the fuel pressure and it was fine (58 PSI'ish +/-) so I changed the fuel filter. No change in the idle or codes. I then tore down the top end and got to my injectors and tested them for proper resistance and even hit them with power to insure they were not clogged. All injectors are sound and spray the correct amount of gas. (I measured it). I then tested the injector harness for shorts or melted wires with my voltmeter. There is proper resistance and continuity. sooo fuel was good.

FIRE::::I replaced the plugs and plug wires. So I got out my spark tester and notice that cylinder 6 on the front bank was not good by a long shot. So I installed a new coil pack. I tested the wire harness for shorts or melted wires with my voltmeter. There was proper resistance and continuity. Drove a few days and when the CEL came on the only code was P0301. P0300 SOLVED I had a bad coil pack. I then went to compression testing on CYL 1. The Compression was right around 130 I think, anyway. So I had fuel and fire and good compression WHAT THE HECK. As I went to put the plug back in I notice the ceramic tip of the new plug was broke and was closing the gap of the new plug. Went and got a new plug an Drove a few days and the CEL never came on. P0301 SOLVED. New plug went bad. Rough idle remained but not as bad as it was. We drove for about a week then one night I stopped at a red light and MY GOD you would have thought I was riding a bull. That engine starting stumbling and spitting so bad I had to put it in natural and rev the engine to keep it going but once I started going it went back to a smooth ride unless I stopped again then it was back on the bull. Lol AND NO CODES. A few days go by and finally got a code P0508 I replaced the IAC because it was bad (it did not ohm out on the component side). The rough idle remains. Vacuum leak maybe? I HAVE NO VAC LEAKS. I did a smoke test, the spraying of carb cleaner test. A service vacuum leak test (basic and advance) per the Service repair manual and put a gauge on it as well NO LEAKS. Why do I have a rough ideal? Still at this point.

:angrya::confused::nut::angrya::nut::confused:
 

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Drivin' Maniac
2002 Grand Caravan ES 3.8L
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You say you did an ohm meter test of the injector wiring harness.


But

Did you unwrap the wires to see if the insulation was melted? This is a known issue with these vans. And the problem might only show up when the engine is running (shaking), not statically.




ALSO

Did you use the Double Platinum spark plugs as fitted by the factory? Some say they are the only ones that work with the waste-spark system used by Chrysler. Gap is important, as well...if the platinum pads fall off the electrodes the gap is double the spec.


PS: You seem very methodical in your troubleshooting. Nice work. :thumb:
 

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Hi guys, I'm new to this forum and a novice home mechanic. I have a 2004 Chrysler town and country. I need to replace the ignition coil pack. I just had a tune up and I'm still having a rough idle. My mechanic friend suggest I replace the coil ack. How the **** do I get this out. I looks like I need to remove the steering fluid reservoir to gain access to the coil pack bolts. But how does the steering fluid reservoir release off the top of the coil pack. I unscrewed the two bolts but it's still stuck firm on the mount. Any suggestions. I'm sure its something simple that I'm over looking.

Thanks

Joe
 

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how does the steering fluid reservoir release off the top
There is a lower bolt that the rear nut needs to be loosen, but not removed. That bolt/nut clamps the reservoir on to a bracket. Remove the pressure and the reservoir will pull up and off the support bracket.

Now, let's get back on topic.
 

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Did you wiggle or pull and push the fuel injector harness under the exhaust when checking short/continuity? The harness under the exhaust is a well known problem for the van

Does the misfire happen only at idle or also at load?
If only at idle, did you wiggled the vacuum hoses to the intake manifold when measuring the vacuum?

Did you test you sensors and their wires (wiggle the wires when checking them)? MAP sensor, TPS, IAT sensor, CMP sensor, and CKP sensor. When check wires, pay attention to the locations close to exhaust and metal edges.

Did you check the 5V volt reference voltage to the sensors and signals from the sensors?

An oscilloscope will be helpful. You can back-probe a sensor power and signal and see the changes. If you have an ignition pickup coil, you can synchronize the ignition spark line with other signals to check ignition timing and fuel injector timing. Be careful. A circuit can be shorted when back-probing and PCM can get fried.
 

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Discussion Starter #6 (Edited)
Hey all happy thanksgiving.
thanks for the in put and lets me try to answer them.
1. I did not unwrapp the wire harness and look for melted wires. The reason I did not. Is if one is melted it would cause a short to ground and the fact that I had proper resistance and continuity and voltage. I ASSUMED. I had no melted wires. Im I wrong:Wow1:

2 yes I put factory plugs in. I had not cussed my dealership out over prices in a while so I took care of 2 birds with one stone:biggrin:

3. I tested a few of the sensors for the proper voltage.but seeing as im not getting a Dtc for any of the circuits I have not went thru each and everyone. I did it for the IAC, MAP, TPS. IM I wrong in ASSUMING they are good if I get no DTC:Wow1:

4. The misfire is cured, but it was present all the time. Now its gone and the rough ible is only present when going a very very low speedslike backing out of a parking space speed.

5. The 5 volt refernce was present on the ones I did check.

6. I wish I had a scope.:thumb:. But I tore it down again today just to look at everything again. And im sad to report. Its all ok.i was hoping I was missing something. I did find it odd the cylinder 1's plug was wet. But the plug is firing. And the gap is fine. I hate to say it but I'm thinking PCM. The reason is I got the codd of death about 5 months ago P0601. I paid autozone 200+ for a reprogrammed one. HUMMMMMM?

7 did not wiggle the vacuum lines because I had the proper vacuum.i like the idea of wiggling the wires and vac lines. But the idle issue is present Only when starting, or stopping at redlights. Other than that it runs some as a new caddy.if a wire or line was bad would the oppisite not apply? Idle fine until I hit a bump or something like that.
 

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Idle fine until I hit a bump or something like that.
Seems to be intermittent electric wire short or a bad contact at a connector. A bump can expose the problem. It is a pain to trace this kind of problem.

When it runs fine, open the hood and wiggle the harnesses one by one to see which is associated with the misfire. Use a long wood stick for the dangerous areas. Don't use your bare hand!

My understanding is that a bad sensor is not necessarily to set a DTC. For instance, a MAP sensor or TPS reports incorrect info to PCM and PCM will think the sensor functions properly but use the wrong info to control fuel.

BTW, a bad O2 sensor can cause misfire by incorrectly reporting a rich condition to the PCM such that the engine runs too lean. EGR valve is not open at idle and exhaust gas through a faulty EGR system also results in misfire at idle. Not sure whether a mechanical issue of EGR can lead to the symptom, but it should be easy to use a screw drive to tap EGR for a quick check.
 
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