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While you have the plenum off, swap that injector from the misfiring cylinder to any other position. No gaskets should be required, if sticky trying to get them out, use a little silicon spray, but they should just pull out.

Reset the PCM / codes and then if the fault follows the injector to another cylinder, then "there you have it"

I can't wait to get this fixed and learn the conclusion... cheers!

*note, while I am sure you are anxious to get back on the road, I suggest that you are working methodically and don't change everything at once. If you change a lot of things and then if fault goes away, you'll never really know what it was that 'cured' it. Months/weeks/year later if it returns... where are you going to start?
If you want this vehicle to remain as dependable as an airliner, you need to define what is truly the fault and that it is definitively fixed.
 

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Is there a o2 sensor up front on the 2006 3.3, the upstream?
If there wasn't an upstream, there wouldn't be a downstream...
Every production gasoline vehicle from the last two decades has one (at least the ones made by 'major' automakers).
 

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I understand upstream/downstream. I guess I was asking if the 06 o2 sensor had one located towards the front. My 2002 have them behind, at the firewall. I've not worked on an 05-06 o2 sensor.
Will it misfire as before if you unplug the front O2 sensor? (and cause it to run "open loop" - pre-set fuel map instead of rich/lean feedback from sensor)
 
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Discussion Starter #25
Well I spent a couple more hours on it this morning , I pulled the injectors & swapped 6 & 4 , the #6 injector was far cleaner on the tip then the others maybe suggesting excess fuel , I cleaned up the tips on all of the injectors while they are out & put everything back together & drove it 15 miles , for the first 5 mins it ran perfectly [Yahoo!] then it went closed loop & started dropping cylinders like crazy , it is now running worse than before at times [uggg], so I expected to see P-0304 the crazy part now is there is no codes at all .
So it seems to be something to do with warming up & switching to closed loop , where before it was dropping cylinders when cold but would pick them up within a min or so running better as it warmed up .
I will try running it with the O2 unplugged in the morning see what that does .
 

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Drivin' Maniac
2002 Grand Caravan ES 3.8L
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It takes MANY misfires to set the CEL, as stated. Use the OBD scanner to check for misfires.
 

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well something you did made a difference, that is something that can be worked with.

Did you look in the top of the injectors? each one has its own, individual, filter screen. The screen can be removed with the proper size wood screw (maybe #8 or #10) but a regular screw, not a long pointy drywall type screw. You want to gently grab the brass ring of the 'basket' filter without too much penetration that could damage the screen mesh, then pull the filter straight out (it is a press fit)

You can also improvise injector cleaning with something like a carb cleaner or even liquid injector cleaner (the stuff that you might add to the fuel tank) with an eye dropper. Then use a 9volt battery to *tap tap tap open the injector so the stuff goes down inside, let is soak.
[ I have filled a 8" length of fuel hose that slides over the top of the injector and clamped. Filled that hose with fluid (I've used gasoline, mineral spirits, and even WD-40) and then applied 40 psi air pressure. Then I used my 9volt battery to 'trigger' the injector and could watch the spray pattern of each injector one by one. (You might even use Techron or Berrymans or SeaFoam or any type of carb / injector cleaner) and I have restored injectors to working in a pinch.

**Another thing to consider is if you are getting full pressure from your fuel injector pump. Located in the fuel tank and tested at the fuel line that flows into the fuel rail with a pressure gauge. Around 45 PSIG if I remember correctly.

Work safe, work clean...
 

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Discussion Starter #28
No I didn't look in the top other than the 2 I swapped , I didn't want to damage a seal as I don't have spares here , I swapped fuel pumps about 18 months ago when it died & Left me stranded away from home , why don't they fail in the driveway ?? I believe the fuel pressure is good , it starts easily & has great power when all 6 fire . I had no time today to play with it but it did run well cold this AM , tonight cold it ran like crap again , I will disconnect the O2 & see what that does . I may also pull a valve cover & look at the valve springs . Still no codes & the engine light is off .
 

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I imagine this is one of the drawback to living south of the border. Sounds like you utilize this van quite a bit when it is running right.

Post a video or two. When it is running good and when it is breaking up.
Sometimes when a member can't post a video direct, they upload to YouTube and then post the link here.
 

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Discussion Starter #30 (Edited)
I lived in Canaduh for 50 years , I tried to move to the US for 33 of those years & there was no way I was ever going to get in so I looked further south & life is good here . Often posted videos are not allowed to be viewed here & it may work the other way that if I post a video you may not be able to view it .
The bad part is it takes about 2 weeks to get parts shipping here which was also the case living in Can. , I need to order parts but which parts ?
I did unplug the O2 upstream & it seemed to run a bit better , I will drive it again today , I know at times it si dropping at least 2 cylinders possibly 3 but is it random or the same cylinders , still there are no codes other than the O2 I unplugged . I am still thinking the ECU could be bad , the wiring visually looks ok , no visable sign of any damage at least . I might pull all of the injectors & try the 9v battery test with fuel or cleaner yet .
 

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Discussion Starter #31
Update
I put another 50 miles on , I swapped the #6 & #4 injector it runs the same ,
I swapped the spark plugs between #6 & #4 as well 4 was white 6 was brown when I pulled them , the plug in #4 is now white & the plug in #6 is turning brown so #6 is still the problem , so it is not the injector ..
I also ran it with the O2 unplugged , seems to run better most of the time maybe ....
I pulled #3 spark plug as well it is also brown so it has to be ign as it fires from the same coil so I pulled off the plug wire while running , it shoots a spark 4" to ground no problem , , I tested the wiring from the main plug under the throttle body to the coil pack & the wiring is fine , clean connections & zero ohms resistance even moving the plugs around . .
I ran the engine up to 2000 rpm in gear , totally smooth , then I idled it down & did it again 2 cylinders would not fire so 10 seconds apart it runs perfect then drops 2 cylinders with the O2 still unplugged .
I can see no damaged wiring between the engine & ECU & why would it totally change 10 seconds apart ?
the only code is the O2 sensor unplugged .
I am back to the ECU as the problem
 

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Update
I put another 50 miles on , I swapped the #6 & #4 injector it runs the same ,
I swapped the spark plugs between #6 & #4 as well 4 was white 6 was brown when I pulled them , the plug in #4 is now white & the plug in #6 is turning brown so #6 is still the problem , so it is not the injector ..
I also ran it with the O2 unplugged , seems to run better most of the time maybe ....
I pulled #3 spark plug as well it is also brown so it has to be ign as it fires from the same coil so I pulled off the plug wire while running , it shoots a spark 4" to ground no problem , , I tested the wiring from the main plug under the throttle body to the coil pack & the wiring is fine , clean connections & zero ohms resistance even moving the plugs around . .
I ran the engine up to 2000 rpm in gear , totally smooth , then I idled it down & did it again 2 cylinders would not fire so 10 seconds apart it runs perfect then drops 2 cylinders with the O2 still unplugged .
I can see no damaged wiring between the engine & ECU & why would it totally change 10 seconds apart ?
the only code is the O2 sensor unplugged .
I am back to the ECU as the problem
Time for a timing chain

Mike S Grand caravan 3.3
 

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The injectors are all powered by the same positive wire in the harness. It is the ECU that grounds the individual injectors to make the squirt. The injectors spray behind the intake valve. Just a few "beliefs" I am stating.... (and as always, I could be wrong)

I think I remember a member in xxxslavia or xxxistan that had jumpered the harness to operate a dropping injector to another injector wiring in parallel. If you get to the point that you are considering throwing an ECU at it, you might want to try that to prove/disprove a theory before busting a nut.

Hopefully atoman voices in (or mikespainting) on my folly
 

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Neil, how about the possibility of an intermittent sticking valve? Have we discussed that as a possibility? Wait, it is two cylinders on the same coil pack...

How about rewire the primary and secondary wiring at the coil to use different coil set for use on different set of cylinders? If the defect follows the coil 'set' to a new set of cylinders then there you have it.
 

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Discussion Starter #35
Might be a timing chain , I can check that out not sure why that would be intermittent tho
this is the 3rd coil on it , , I pulled the valve cover you can eat out of the inside of the engine , it is perfectly clean in there , the valve springs are good
 

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Did you could you check fuel pressure?

We are missing something and it is going to turn out to be something ambiguous.
 

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Discussion Starter #37 (Edited)
No I didn't but last year the fuel pump died & I replaced it with a defective pump it had low pressure & was difficult to start so I replaced it again with a better pump & now it starts right up easily
 

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Discussion Starter #38
Ok so I checked the timing chain , & it makes sense after 270000 miles that it should need one But with a 15 mm 8 " wrench on the crank bolt the wrench moves less than a 1/4" at the end before it takes up the slack in the timing chain , I mean seriously minor slack in the chain at all .
 

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timing chain causing only 1 cylinder to misfire? sounds a wee bit unlikely to me.
I'd throw the flex plate theory, but that's been covered before... (esp. since misfire occurs when torque load is relieved on return to idle)

Any chance you have access to an oscilloscope? and can compare injector timing and pulse width between cyl 6 and others?
If you can establish that PCM is indeed sending a different pulse to #6 injector, then it would point to either Crank/CAM signal problem or PCM / wiring fault.

Personally, I'd avoid putting two injectors on one PCM driver unless everything else is covered, but that could be attempted as a "poor man's" diagnostic aid (it just won't be very conclusive).

There is a very far fetched chance that a cam lobe on 6 is wearing out and not opening the valve (to same extent). There were a couple of reports on here about engines missing on a particular cylinder at idle speed only (while running fine at higher speeds) and after everything else was tried, lifters were pulled to reveal cam damage. IIRC, those reports were about circa '05 or '06 models with 3.8 that are somewhat known to use oil and service history wasn't stated on those engines so I have no confidence this can occur on a well serviced 3.3 engine (just mentioning it)
 

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Discussion Starter #40
Timing chain makes sense with the milage but not misfiring 2 cylinders on the same coil , as above 6 & 3 the plugs are discolored , it seems to be misfiring the 3rd coil furthest from the intake , it never coded #3 but the plug is brown just like 6 & they both fire from the same coil so it has to be ignition related , I have had 3 coil packs on it , 2 known to be good something is not triggering the coil while the wiring seems fine from what I can test , all of the wires under the intake test fine .
SO back to the Ecm ??, no codes for cam or crank sensor , actually no codes at all & not consistant misfire sometimes firing all 6 & sometimes not .
 
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