3.5 mystery misfire - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat
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post #1 of 96 (permalink) Old 06-17-2012, 01:03 AM Thread Starter
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3.5 mystery misfire

3.5 ES car will misfire or stumble @ 2000+rpm the problem is worse at exactly 2k rpm where it will miss/stumble repeatedly, or at least every one second..... at above 2k rpm the miss/stumble will happen about every 5-10 sec.... when the hood is popped and listening to the problem you can hear a slight hiss type noise (best i can describe it) coming from cylinder 3 or 5 area but only when the stumble happens.... about once a trip the cruise light will flash only when the stumble happens (usually on freeway at around 2.3k).... also while at idle a small clank can be heard from the #3 or #5 cylinder right where the valves are (its very quite and can only be heard if you really listen or put ear close) my dad said it was a lifter or valve sticking and eaither a oil change or oil additives will fix that?..... tach (means rpm gage right? ) will vary on the misfire its hard to explain, while in park, about 70% of the time the missfire will drop rpm only about 100-200 but other times the rpm will drop 300-600 rpm.

things already tried

1)fixed pinched fuel line
2)replaced fuel filter
3)new crank sensor (ended up new sensor was bad and the original worked better have not tried a new "working" sensor)
4)replaced drive belts/water pump/timing belt/ TB tensioner (more just needed to be done then assumed the problem)
5)replaced faulty coil pack (read 16.4 ohms with new pack reading 12)
6)plugs were replaced about 100 miles or less before the problem started
7) sprayed carb cleaner around manifold gaskets and intake hoses with no vaccum leak detected
8)just tested the wire ohms today and they dont seem right to me they are as follows
#1-12.6
#2-20.7
#3-18.2
#4-22.8
#5-20.4
#6-21.9
seems even worse when they are lined up next to each other like that

is it possible the lifter/valve sticking as mentioned before could be causing the misfire? or possibly the timing is slightly off?(i would assume it wouldnt only effect the #3 or #5 lifter but instead the whole side of the block thats off) but just your opinions would be appriciated

the engine is throwing NO CODES, no MIL or key dance codes as far as the car is concerned nothing is wrong besides the rare cruise light flash.

i feel my next course of action will likely be new wires depending if they are good or not, then, if nothing else look into compression/vacuum test, and getting the car plugged into a scan tool.

only good thing from all this everything i have replaced so far needed it
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post #2 of 96 (permalink) Old 06-17-2012, 03:34 AM
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you said that you have already tried the crank sensor. judging by the rpm that this happens at, I would more likely suspect the camshaft position sensor (although that would usually throw a code).
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post #3 of 96 (permalink) Old 06-17-2012, 05:43 PM
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The 1st gen intake gaskets were composite gasket material that frequently cracks. Though you sprayed carb cleaner around the intake, you were not able to get to the underside of the intake where it may still be leaking.
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post #4 of 96 (permalink) Old 06-17-2012, 08:36 PM Thread Starter
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Quote:
Originally Posted by Adpros View Post
The 1st gen intake gaskets were composite gasket material that frequently cracks. Though you sprayed carb cleaner around the intake, you were not able to get to the underside of the intake where it may still be leaking.
thats one of the things i was thinking when i was spraying it because i noticed even after taking off the black metal cover on the penilem or w/e its called, i still couldnt get much access to spray the lower gasket


can anyone verify those plug wire resistances??

also is their a way i could test the cam sensor with my multimeter instead of throwing 50$ into a maybe solution
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post #5 of 96 (permalink) Old 06-18-2012, 10:39 PM
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When were the spark plug wires last replaced? They can easily wear out at 30K miles. Measuring resistance is not sufficient. A wire can become more inductive with wear.The connection from the wire to the coil pack can also easily corrode. When the spark plugs were replaced, did you use Champion coppers? The electronic engine control system is designed to work best with those plugs. If I were you, I'd first spring for a new set of wires. Use dielectric grease at the ends to block moisture.
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post #6 of 96 (permalink) Old 06-18-2012, 11:38 PM Thread Starter
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When were the spark plug wires last replaced? They can easily wear out at 30K miles. Measuring resistance is not sufficient. A wire can become more inductive with wear.The connection from the wire to the coil pack can also easily corrode. When the spark plugs were replaced, did you use Champion coppers? The electronic engine control system is designed to work best with those plugs. If I were you, I'd first spring for a new set of wires. Use dielectric grease at the ends to block moisture.
champion coppers, yes, i checked the connections on the inside of each end of every wire when i tested em and no corrosion was visible, no idea when last replaced, they were all lacking grease but i doubt that would cause an issue??

what is the resistance range per foot of wire... ive herd 3000-5000/ft and 2000-4000/ft???

Last edited by Ruggels; 06-18-2012 at 11:41 PM.
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post #7 of 96 (permalink) Old 06-20-2012, 03:33 PM
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IMO ohm readings on your wires are high, you should read like 4-6K per foot, get some new wires or take your meter to the parts store and ohm a new wire.
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post #8 of 96 (permalink) Old 06-20-2012, 03:37 PM
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BTW - I had the plug boot end on one of these cars that was arching badly to the tube in the valve cover and causing a misfire and it actually didn't ohm badly.
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post #9 of 96 (permalink) Old 07-02-2012, 01:10 AM Thread Starter
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i did the plug wires after reading the ohms of the new wires at the store, still no fix and ordered the manifold gasket when i got the wires, any other gaskets i should replace while im inside,,, and i cant seem to find much in the forums about the manifold anyone have any advice?
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post #10 of 96 (permalink) Old 07-02-2012, 10:48 AM
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Quote:
Originally Posted by Ruggels View Post
i did the plug wires after reading the ohms of the new wires at the store, still no fix and ordered the manifold gasket when i got the wires, any other gaskets i should replace while im inside,,, and i cant seem to find much in the forums about the manifold anyone have any advice?
Be careful removing the bolts near the thermostat housing, they tend to seize up. If the bolt looks rough replace it. While you are in there I would replace the injector o rings while you can get to them, its cheap and easy. If your valve covers are leaking you should do those now as well.
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post #11 of 96 (permalink) Old 07-04-2012, 05:02 PM
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Hell I would throw a PCv , and valve cover gadgets while you have the chance. Clean the TB's.
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post #12 of 96 (permalink) Old 07-07-2012, 04:35 AM Thread Starter
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finally have the day off tomorrow and the gaskets came in so i started as soon as i got home from work i got the entire manifold taken off and gunna call it a night at that, just a few questions before proceeding tomorrow....

dispite my best efforts (prob coulda been better) it would seem some debris has found its way into one or 2 of the valve cylinders its minimal but i still want to get it... how much would a little debis hurt?.... how hard is it to get to the actual valves, from what i can see if i remove the valve covers i still wouldnt be able to get to were i need?

should i use a gasket sealant? ive heard its not required but better safe then have to pull it all back out right?

since im this far into the engine already i figure might as well do the injector o-rings, PCV valve, valve cover gaskets,... would it help to replace the break booster valve as well?

and throttle body was surprisingly clean the rest however.... is not ive sprayed much down with TB cleaner to sit over night but i dnt think thatll do the trick its really caked on any advice on cleaning?

edit: oh yea and every gasket ive seen so far has been bad enough to crumble very very easily

Last edited by Ruggels; 07-07-2012 at 04:40 AM.
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post #13 of 96 (permalink) Old 07-07-2012, 12:20 PM
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Since you're dealing with a 1st gen 3.5L, I don't think I'd mess with the injector O-rings unless you already have evidence of leakage. The injectors are seated in a rail that is removed by three bolts. If you remove these rails, you won't have to mess with the injectors directly. Just lift all three per rail at a time. There is a gasket below the rail that is made out of the same material the intake gasket is made of so, you'll probably find these are crumbling as well.

The reason I mention leaving the injectors in is because removing them from their rails is a job that requires a bit of finesse to prevent fracturing the rail they are set into. If you do end up pulling them out, there are a couple more O-rings at the ends of the fuel rail to deal with as well.

One last bit... Don't try pulling the injectors from their electrical connector! Instead, find a chunk of hard wood or plastic and carefully push them out from the pintle end.
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post #14 of 96 (permalink) Old 07-07-2012, 01:06 PM Thread Starter
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yea ive already taken out the fuel rail only reason ive thought about doing the injectors is because ive heard that their was a recall on them causing a leak?
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post #15 of 96 (permalink) Old 07-07-2012, 01:22 PM
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Yes, there was a recall. Trying to remember now was it #790? I will look and see what the actual number is.

If you can get the recall kit, it has all the gaskets and O-rings for the rails. It would probably have to be special ordered for you as most dealers won't stock a recall part from so long ago.

EDIT:

Yep, it's #790

It also dealt with gluing on reinforcement strips to the fuel rails to prevent them from busting. You'll likely find these are already stuck to your rails.

The kit is part number: CAXJ7901

Last edited by Adpros; 07-07-2012 at 01:30 PM. Reason: More Data
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