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Random idle miss when cold

2nd Gen Neon 2000 - 2005 2nd Gen Neon

Random idle miss when cold

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Old 05-12-2019, 05:50 PM
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Default Random idle miss when cold

I've been noticing a random miss at idle in my '04 2.0. Usually happens right after starting it when engine is cold. Once it warms up to normal temp, it has no issues. Not getting any check engine light. What should I be checking?
 
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Old 06-10-2019, 12:37 PM
paw paw
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Could be spark breakdown under the plug wire boot due to moisture, that gets boiled off / evaporated as the engine warms up. So in the morning before starting, maybe pull the plugs & wires to look for moisture, or carbon tracking signs, or maybe oil signs from a leaking cam cover gasket. Also check / set the spark gap with a Wire gauge tool.

Check the plugs internal & external ceramic insulators for chips or cracks, or signs of carbon tracking. The plugs internal insulator should not be carbon, or oil fouled. The external insulator should be clean, no chips, cracks, or carbon track signs. Inspect the plug wires & boots on Both ends for splits or cracks.

If all look ok, butter on a thin layer of good quality di-electric grease, like GE, Dow Corning, Permatex / Loctite, inside the plug boots & onto the Outside of the plug insulators. This will cut down on flash over on damp dewy morning starts, or rainy days.


After dark with it cooled down, raise the hood & start it up to look at the coil pack & plug wires for a arcs & sparks light show from faulty insulation. You could also try a "wet down test" by using a spray bottle of water to spritz the coil pack & individual plug wires, to see if you find, or cause some arcs & sparks from borderline insulation.

If no joy there, use, or rig a stethoscope from a length of rubber tubing, one end to your ear, the other end on each fuel injector, to determine if one sounds different & if so, make sure its electrical connector, wires, pins / sockets are locked in place / not pushed back & that the pins / /sockets are clean, not bent or broken or pushed back.

When the miss is felt, do you hear any unusual engine noise in time with the miss, like a valve tick, or clatter that goes away as the engine warms up ?

If all that checks out, then maybe consider trying a 1oz/gallon dose of Techron Concentrate Plus in the tank at the pump before filling so to get good mixing & if we'll use Chevron, Texaco, CalTex, or now Shell fuel, which have some PEA in their fuel ad pack, the additional 1oz / gallon Techron will raise the treat rate about 10X above that of pump gas alone, so can often tidy up the fuel injectors, intake valves, piston crowns & combustion chambers in one treatment. If we'll run most of the treated tank out, with daily rpm run up's to 3500 for a mile or two it'll blow out loosened deposits.

Some initial thoughts for consideration, let us know what you find.
 

Last edited by paw paw; 06-11-2019 at 09:18 AM.
  #3  
Old 06-10-2019, 11:16 PM
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Originally Posted by paw paw View Post
Could be spark breakdown under the plug wire boot due to moisture, that gets boiled off / evaporated as the engine warms up. So in the morning before starting, maybe pull the plugs & wires to look for moisture, or carbon tracking signs, or maybe oil signs from a leaking cam cover gasket. Also check / set the spark gap with a Wire gauge tool.

Check the plugs internal & external ceramic insulators for chips or cracks, or signs of carbon tracking. The plugs internal insulator should not be carbon, or oil fouled. The external insulator should be clean, no chips, cracks, or carbon track signs. Inspect the plug wires & boots on Both ends for splits or cracks.

If all look ok, butter on a thin layer of good quality di-electric grease, like GE, Dow Corning, Permatex / Loctite, inside the plug boots & onto the Outside of the plug insulators. This will cut down on flash over on damp dewy morning starts, or rainy days.


After dark with it cooled down, raise the hood & start it up to look at the coil pack & plug wires for a arcs & sparks light show from faulty insulation. You could also try spritzing the coil pack & plug wires with a spray bottle of water to see if you find, or cause some arcs & sparks from borderline insulation.

If no joy there, use, or rig a stethoscope from a length of rubber tubing, one end to your ear, the other end on each fuel injector, to determine if one sounds different & if so, make sure its electrical connector, wires, pins / sockets are locked in place / not pushed back & that the pins / /sockets are clean, not bent or broken or pushed back.

When the miss is felt, do you hear any unusual engine noise in time with the miss, like a valve tick, or clatter that goes away as the engine warms up ?

If all that checks out, then maybe consider trying a 1oz/gallon dose of Techron Concentrate Plus in the tank at the pump before filling so to get good mixing & if we'll use Chevron, Texaco, CalTex, or now Shell fuel, which have some PEA in their fuel ad pack, the additional 1oz / gallon Techron will raise the treat rate about 10X above that of pump gas alone, so can often tidy up the fuel injectors, intake valves, piston crowns & combustion chambers in one treatment. If we'll run most of the treated tank out, with daily rpm run up's to 3500 for a mile or two it'll blow out loosened deposits.

Some initial thoughts for consideration, let us know what you find.
Had new wires on it when I bought it, I put fresh Champion plugs of correct heat range. Approximately 1500 miles on them. Seems to occur mostly when I press down harder on the gas pedal, when I touch the gas normally in town driving it does not do it. No unusual noises heard. I did a resistance check on the ignition coil, Here are the results:

Primary resistance
Cyl 2&3= 2 ohms
Cyl 1&4= 2 ohms

Secondary resistance

Cyl 1&4= 12,000 ohms
Cyl 2&3= 12,000 ohms
 
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Old 06-11-2019, 03:21 AM
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Ok, good feedback. The secondary coil resistance is within range, but the primary resistance is Way over spec. It should be around 0.5 ohms, so I'd suggest measuring the primary resistance again.

Since we have a "waste spark' ignition system, the spark plug gap will stay in spec Way longer if the plugs are of the fine wire iridium enhanced center electrode, with platinum, or iridium pad side wire design.
On the waste spark ignition system, half of the plugs get a normal polarity spark emanating from the center electrode to the side wire ground lug. The other two plugs get a Reverse polarity spark which eminates from its side wire ground lug to the center electrode. Since the waste spark system fires its plugs on Every rotation of the crank shaft, firing a plug on its power stroke, then again on the next crankshaft rotation when its on its Exhaust stroke (Waste Spark), thus working its ignition system parts Twice as hard as a conventional coil system, so the components need to be designed to take the Double work load & survive.
So to eliminate excessive spark gap erosion, the ground lug needs at least a platinum pad, or better still a iridium enhanced pad, as iridium has a much higher melting point, so the enhanced iridium electrode design has its spark gap stay in spec Much longer than conventional nickel, or platinum electrodes.

The iridium enhanced fine wire center electrode plugs make a much hotter spark kernel & require less voltage to fire, so we get going quicker on those cold winter morning starts when battery voltage is at its lowest because the battery is cold & less efficient & it has to crank the cold engine, run the fuel pump & fire the spark plugs with a good hot spark kernel to get us going. The fine wire plug also makes a more concentrated / hotter spark kernel so it won't blow out, or go wimpy when we lug the engine on a pull, or when we wind it out when we go at throttle up.
I get faster year round starts on all of our family fleet vehicles, half of which are waste spark & half which are conventional, or distributor ignition systems.

Just because the plugs & wires are new doesn't automatically mean their good, make em prove themselves with a wet down test, or at least raise the hood after a long cool down period on a cool humid evening after things get coated with dew, or a over night dew soak, start it cold & look for a arcs & sparks light show. The wet down stress test is even better to make the wires, coil pack & plugs prove themselves.

If it misfires when you load the engine at throttle up, it suggests a spark problem, like a wimpy spark from the coil pack, or too wide a spark gap, or maybe a lean mixture.
If it's a misfire, the computer should have a code clue stored that could help focus your trouble shoot,

If the problem is from a lean air / fuel ratio, you may have wimpy fuel pressure, clogged fuel filter, wimpy fuel pump, old lazy / slow switching O2 sensor, or dirty fuel injectors causing a lean squirt that'll corrupt fuel trim & cause the engine to stumble under load. So you can see we need more clues to begin to narrow down the suspect list some.
 

Last edited by paw paw; 06-11-2019 at 08:50 AM.
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Old 06-11-2019, 04:43 PM
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Originally Posted by paw paw View Post
Ok, good feedback. The secondary coil resistance is within range, but the primary resistance is Way over spec. It should be around 0.5 ohms, so I'd suggest measuring the primary resistance again.

Since we have a "waste spark' ignition system, the spark plug gap will stay in spec Way longer if the plugs are of the fine wire iridium enhanced center electrode, with platinum, or iridium pad side wire design.
On the waste spark ignition system, half of the plugs get a normal polarity spark emanating from the center electrode to the side wire ground lug. The other two plugs get a Reverse polarity spark which eminates from its side wire ground lug to the center electrode. Since the waste spark system fires its plugs on Every rotation of the crank shaft, firing a plug on its power stroke, then again on the next crankshaft rotation when its on its Exhaust stroke (Waste Spark), thus working its ignition system parts Twice as hard as a conventional coil system, so the components need to be designed to take the Double work load & survive.
So to eliminate excessive spark gap erosion, the ground lug needs at least a platinum pad, or better still a iridium enhanced pad, as iridium has a much higher melting point, so the enhanced iridium electrode design has its spark gap stay in spec Much longer than conventional nickel, or platinum electrodes.

The iridium enhanced fine wire center electrode plugs make a much hotter spark kernel & require less voltage to fire, so we get going quicker on those cold winter morning starts when battery voltage is at its lowest because the battery is cold & less efficient & it has to crank the cold engine, run the fuel pump & fire the spark plugs with a good hot spark kernel to get us going. The fine wire plug also makes a more concentrated / hotter spark kernel so it won't blow out, or go wimpy when we lug the engine on a pull, or when we wind it out when we go at throttle up.
I get faster year round starts on all of our family fleet vehicles, half of which are waste spark & half which are conventional, or distributor ignition systems.

Just because the plugs & wires are new doesn't automatically mean their good, make em prove themselves with a wet down test, or at least raise the hood after a long cool down period on a cool humid evening after things get coated with dew, or a over night dew soak, start it cold & look for a arcs & sparks light show. The wet down stress test is even better to make the wires, coil pack & plugs prove themselves.

If it misfires when you load the engine at throttle up, it suggests a spark problem, like a wimpy spark from the coil pack, or too wide a spark gap, or maybe a lean mixture.
If it's a misfire, the computer should have a code clue stored that could help focus your trouble shoot,

If the problem is from a lean air / fuel ratio, you may have wimpy fuel pressure, clogged fuel filter, wimpy fuel pump, old lazy / slow switching O2 sensor, or dirty fuel injectors causing a lean squirt that'll corrupt fuel trim & cause the engine to stumble under load. So you can see we need more clues to begin to narrow down the suspect list some.

No check engine light on, no codes. The plugs I put in, were the ones called for on the emissions decal, RC9YC. So, should I upgrade to the iridium plugs? I re checked primary resistance and is same as I previously tested. The "cutting out" only happens when I press down on the accelerator, like for going up a hill or passing. When I take off from a stop, or at cruising speed it runs smooth as silk with no problem
 
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Old 06-11-2019, 06:41 PM
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Well lets see, was it doing the "cutting out" Before you changed the plugs?
How are you scanning for trouble code clues?
Is this a manual, or auto tranny?
 
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Old 06-11-2019, 06:51 PM
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I don't believe it was. To scan for codes I have an Actron OBD 2 code scanner. Automatic transmission. If I need to go with the Iridium, which brand is the best?
 
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Old 06-11-2019, 07:22 PM
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Ok, if it wasn't doing this Before the plugs were replaced, then remove them for Careful inspection of the external & internal ceramic insulators, looking for chips, cracks, or damage to the center electrode or the ground side wire, especially if you dropped one.

Did you have to adjust the spark gap & if so what gap setting did you use?

No need to toss the plugs if they check out ok, at least try to get some use from them before replacing.

What plug is best is sorta subjective. Correct heat range is really important. My records show I replaced the OEM plugs in the Wifes 2000 Neon with the Autolite fine wire iridium enhanced center electrode, with platinum pad sidewire, XP3923 @ .035 gap & Autolite plug wires at 35K because it had a miss on a pull. The new plugs & wires stopped the miss. It has 122K on it now & so far & no return of the miss on a pull.
I'd also perform a end to end resistance reading on the plug wires too & do so while flexing the wires on both ends & post the ohm readings on each plug wire.

Is the coil pack OEM, or is it a after market part?
 
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Old 06-11-2019, 08:42 PM
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Originally Posted by paw paw View Post
Ok, if it wasn't doing this Before the plugs were replaced, then remove them for Careful inspection of the external & internal ceramic insulators, looking for chips, cracks, or damage to the center electrode or the ground side wire, especially if you dropped one.

Did you have to adjust the spark gap & if so what gap setting did you use?

No need to toss the plugs if they check out ok, at least try to get some use from them before replacing.

What plug is best is sorta subjective. Correct heat range is really important. My records show I replaced the OEM plugs in the Wifes 2000 Neon with the Autolite fine wire iridium enhanced center electrode, with platinum pad sidewire, XP3923 @ .035 gap & Autolite plug wires at 35K because it had a miss on a pull. The new plugs & wires stopped the miss. It has 122K on it now & so far & no return of the miss on a pull.
I'd also perform a end to end resistance reading on the plug wires too & do so while flexing the wires on both ends & post the ohm readings on each plug wire.

Is the coil pack OEM, or is it a after market part?
I gapped the plugs @ .035 per the emission label. I believe the coil pack is aftermarket, from the light grey color. The high primary resistance makes me think the coil pack is having issues under load. I'll try to check the plug wires tomorrow. What are the resistance specs for the wires?
 
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Old 06-12-2019, 08:31 AM
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Good idea to also check the plug wire resistance.

We have access to the Parts & FSM's here. https://dodgeforum.com/forum/2nd-gen...s-manuals.html
Not sure which engine you have, but you can find the coil pack & plug wire resistance values for your engine in the Parts & FSM's, Ignition section link that Mod darthroush put up for us to access / read, or down load in his #2 post. Click on the Red year range that covers your 04 to open the FSM.

The Field Service Manual / FSM resistance values for the 03 - 05 years plug wires are more Liberal / Wider resistance range, than the values listed for the 00-02 years of our 2.0L, which call out Different Max-Min resistance values for plug wires #1-#4 & #2-#3. So seeing as you seem to have a under load miss at throttle up, I'd be inclined to be more persnickety about the wire resistance range, like called out for the 00-02, 2.0L engine.

EDIT: While in the FSN Ignition section, note the Coil Pack info about Primary & Secondary winding resistance readings & about how to determine coil pack Mfgr by the tower plug wire metal contact color difference.
Also of interest, on the coil pack pictorial note which plugs get the + & - polarity spark & the info I posted about where the spark emanates from, then have a look at the old plugs electrodes to see how they look for wear.

Any plug design of the correct heat range will work in our waste spark system, but platinum enhanced electrodes spark gap will stay in spec longer than the nickel electrode & iridium enhanced electrodes will last longer than platinum because it has a much higher melting point than nickel, or platinum, so the spark gap opens more slowly over time, so its spark gap stays in spec longer.
The Fine Wire iridium enhanced center electrodes make for a more concentrated / energy dense / hotter, spark kernel, that can get us going quicker in winter when the battery voltage is lowest & cold fuel is more difficult to light off.
It can also better light off lean air/fuel mixtures when we go at throttle up any time of year. I think this is why I've noticed quicker year round starts with this plug design.

The even newer design iridium fine wire center electrode with attached fine wire iridium enhanced side wire button, might make for a lifetime spark plug, as with Both electrodes being iridium enhanced, its spark gap will open up Really slow.
Don't know that its needed in our normally asperated engines, but it seems to be the latest top tweak available to the iridium enhanced fine wire design & might be a life time plug design. Go for it in the proper heat range if you like & let us know how it performs.

When you changed the plugs, did you also do a plug read, so you could get a grip on what is going on in each cylinder, like if the plug deposits look dramatically different between cylinders ?
 

Last edited by paw paw; 06-12-2019 at 11:01 AM.

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