Interesting dealer visit...

[phattpat]

I apologize if this has been discussed before - I did a quick search and couldn't find anything. Anyway...

So, I've had the SXT Mag for a few weeks now, and love it. I bought it used from a DCX employee, with about 18k on the clock. I noticed after having it a bit, that on the highway at around 60mph in overdrive (2k rpms, +/-), I'd get a really bad vibration through the car. I knew right away that this was not a tire ballance problem. It resonated throughout the whole cabin of the car very strongly, and if I depressed the gas pedal more (still keeping it in o.d.), the vibrations would get worse. I could go the same speed at different rpms, and it would not vibrate like that. I literally thought the wheels were about to fall off. I rotated all the tires, reballanced them myself (at work), and even had Discount Tire ballance them... and the same thing still happened.

So, I kind of deal with it for a few weeks, and then the other day, I get a check engine light. I'd been wanting to take it to the dealer anyway, just to make sure the car was up to snuff on recalls/tsbs/etc., and the light was good motivation to do so. I know one of the service reps at this particular dealer, and know he'll take care of the car.

Two days later, I get the car back. The error code was P0306 - Misfire. My guy told me that the issue is usually caused by excessive carbon build up on the valves, which was a *common* 'issue' with the 3.5L. He said that due to the design of the cylinder head, carbon was prone to build up on the valves and the exhaust passages leading out of the cylinder head, which could cause the valves to not seat properly, cause misfires, etc. The fix was to 'de-carbon' the valves, and 'rotate the valves'. Not move them from cylinder to cylinder, but actually spin them in place (which I thought most valves do by themselves anyway??). I believe the decarbon process they used this time was to 'soak' the engine. He said if/when it happens again, they usually will do the same thing but may include a valve spring replacement. And, if/when it happens after that... it'd probably be a cyl head swap.

Cool... just what I want to hear about my new car.

He went on to say that they've had that issue with just about every 3.5L-powered DCX vehicle so far, and that it's usually pretty recurring. I asked if there was anything I could do to help prevent that condition - ie, run fuel injector cleaner or Techron regularly... he said: "Nope...not much you can do." He mentioned that the misfire/carbon issue was also 'probably' the cause of my vibration problems, as they could not replicate it after the decarbon-izing of the motor (but they DID notice the vibe before the engine repair).

SO... that's about the whole long story. What do you guys think? I haven't had the car up to speed to verify that the vibrations are gone, but will in the morning on the way to work. I'm kind of upset that the carbon problem is because of a design issue with the cylinder head, and as far as I can tell, this is a problem we're just going to have to live with.

[done]

I apologize if this has been discussed before - I did a quick search and couldn't find anything. Anyway...

So, I've had the SXT Mag for a few weeks now, and love it. I bought it used from a DCX employee, with about 18k on the clock. I noticed after having it a bit, that on the highway at around 60mph in overdrive (2k rpms, +/-), I'd get a really bad vibration through the car. I knew right away that this was not a tire ballance problem. It resonated throughout the whole cabin of the car very strongly, and if I depressed the gas pedal more (still keeping it in o.d.), the vibrations would get worse. I could go the same speed at different rpms, and it would not vibrate like that. I literally thought the wheels were about to fall off. I rotated all the tires, reballanced them myself (at work), and even had Discount Tire ballance them... and the same thing still happened.

So, I kind of deal with it for a few weeks, and then the other day, I get a check engine light. I'd been wanting to take it to the dealer anyway, just to make sure the car was up to snuff on recalls/tsbs/etc., and the light was good motivation to do so. I know one of the service reps at this particular dealer, and know he'll take care of the car.

Two days later, I get the car back. The error code was P0306 - Misfire. My guy told me that the issue is usually caused by excessive carbon build up on the valves, which was a *common* 'issue' with the 3.5L. He said that due to the design of the cylinder head, carbon was prone to build up on the valves and the exhaust passages leading out of the cylinder head, which could cause the valves to not seat properly, cause misfires, etc. The fix was to 'de-carbon' the valves, and 'rotate the valves'. Not move them from cylinder to cylinder, but actually spin them in place (which I thought most valves do by themselves anyway??). I believe the decarbon process they used this time was to 'soak' the engine. He said if/when it happens again, they usually will do the same thing but may include a valve spring replacement. And, if/when it happens after that... it'd probably be a cyl head swap.

Cool... just what I want to hear about my new car.

He went on to say that they've had that issue with just about every 3.5L-powered DCX vehicle so far, and that it's usually pretty recurring. I asked if there was anything I could do to help prevent that condition - ie, run fuel injector cleaner or Techron regularly... he said: "Nope...not much you can do." He mentioned that the misfire/carbon issue was also 'probably' the cause of my vibration problems, as they could not replicate it after the decarbon-izing of the motor (but they DID notice the vibe before the engine repair).

SO... that's about the whole long story. What do you guys think? I haven't had the car up to speed to verify that the vibrations are gone, but will in the morning on the way to work. I'm kind of upset that the carbon problem is because of a design issue with the cylinder head, and as far as I can tell, this is a problem we're just going to have to live with.

I have been on this forum for 18 months and I have never heard that "story" I also have prevoulsy owned a 3.5 LH and currently have a 3.5 in the wife's van. No such crap with mine.

[67alecto]

There are a lot of SXT owners on this board, and I don't think I've ever heard of this before.

[ZMagnum]

This is the first time I've heard of this issue. Hopefully my high speed highway driving blows some of that carbon out. I've heard cars that are only driven in the city stop-n-go traffic can get carbon build-up. When I worked for a police department they used to take their patrol cars up on the Interstate every once in a while for a carbon cleaning.

[NC-SXT]

I believe that dealer is full of crapola. Never heard about this on the 3.5l and they have had them a good while. I would check with other dc forums and see if anyof this is remotely true. My guess not.

[fnkychkn]

you guys are too quick with the clubs and pitchforks. although i haven't heard of this happening on an LX yet, this problem has plagued 3.5L and 4.0L engines for the last eight years or so. weak or out of spec valve springs may be the cause of carbon build-up on the exhaust valve stems, resulting in misfires.

here are excerpts from TSBs:

TSB 09-002-03
SUBJECT:
Engine Stumble/Misfire - MIL Illumination
OVERVIEW:
This bulletin involves decarbonizing the combustion chamber and installing
new exhaust valve springs.
MODELS:
1998 - 2004 (LH) 300M/Concorde/Intrepid/LHS
1999 - 2002 (PR) Prowler
NOTE: THIS BULLETIN APPLIES TO VEHICLES BUILT PRIOR TO APRIL
1, 2003 (MDH 0401XX) EQUIPPED WITH A 3.2L OR 3.5L ENGINE (SALES
CODES EGC, EGE, EGG, EGJ, EGK, EGW)
SYMPTOM/CONDITION:
Engine stumble and/or misfire. More noticeable during a light throttle tip-in or when
transaxle goes into lockup (approximately 47 m.p.h.). MIL illumination with Diagnostic
Trouble Codes (DTCs) P0300 through P0306, individual or multiple cylinder misfire.

TSB 09-003-03
SUBJECT:
4.0L Multiple Cylinder Misfire
OVERVIEW:
This bulletin involves inspection of all engine exhaust valves and a decarbonizing
procedure if necessary.
MODELS:
1999 - 2004 (WJ) Grand Cherokee (All Markets)
2001 - 2004 (WG) Grand Cherokee (International Markets)
1999 - 2004 (TJ) Wrangler
1999 - 2001 (XJ) Cherokee
NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A
4.0L ENGINE (SALES CODE = ERH).
SYMPTOM/CONDITION:
The customer may experience an incident of engine misfire during certain vehicle
operating conditons. The misfire may occur when the vehicle is operated between
80 - 112 KPH (50 - 70 MPH) and under light loading conditions, e.g. slight uphill
road grades. This condition may occur at all ambient conditions, but is more
noticeable when ambient conditons are less than 0 C (32 F).
If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also
have occurred due to Diagnostic Trouble Code (DTC) P0300 - Mulitiple Cylinder Misfire.
Various single cylinder misfire DTC’s may also be present. If the frequency of misfire is
high the Powertrain Control Module (PCM) may place the engine in “Limp-In” mode.
The misfire condition may be caused by one or more engine exhaust valves that are
slow to close. Late closure of an exhaust valve may be the result of no valve rotation
and associated build up of carbon on the exhaust valve stem.

[HEMIwoman]

GO FNKY...you are the man...the man with the info!

[Fiveoh]

fnkychkn,

Are there any TSB's on the current 3.5L about this issue? That TSB states that engines built prior to April 2003 experience this problem. However, Mags weren't built then. Are they using the same old engines from 2003 in our new 2005 Mags?

[fnkychkn]

fnkychkn,

Are there any TSB's on the current 3.5L about this issue? That TSB states that engines built prior to April 2003 experience this problem. However, Mags weren't built then. Are they using the same old engines from 2003 in our new 2005 Mags?

as a matter of fact, there is:

TSB 09-005-05 dated dec/2/05

SUBJECT:

Multiple Cylinder Misfire Or Rough Idle

OVERVIEW:

This bulletin involves rotating all engine exhaust valves, decarbonizing the combustion

chamber.

MODELS:

2004 - 2006 (CS) Pacifica

2005 - 2006 (LX) Chrysler 300/Magnum/Charger

NOTE: This bulletin applies to all CS vehicles built after February 1, 2004 (MDH

0201XX) equipped with a 3.5L engine (Sales Code EGN).

NOTE: This bulletin applies to all LX vehicles equipped with a 3.5L engine (sales

code EGG).

SYMPTOM/CONDITION:

The customer may experience occasional engine misfire during certain vehicle operating

conditions.

A MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 -

Multiple Cylinder Misfire. Various single cylinder misfire DTC's may also be present. If the

frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in

“Limp-In” mode.

The misfire condition may be caused by one or more engine exhaust valves that are slow

to close. Late closure of an exhaust valve may be the result of no valve rotation and the

associated build up of carbon on the exhaust valve stem.

[ZMagnum]

phattpat what are your driving habits? Do you get up on the highway a lot? Any WOT? Also, what about fuel? 89 octane?

[phattpat]

Hey guys - thanks for all the feedback! I knew a lot of you on here have had your 3.5L Mags/300s for a while with no problems... it's refreshing to hear that not many other people have experienced this yet.

Fnkychkn- thanks for the awesome info!

zxlwno - driving habits are varied...but I do tend to be aggressive at times. WOT on occasion, pretty normal highway/city stuff other than that. But as I mentioned, no telling how the previous owner drove it. Coulda been a grandpa that never got above 3k rpm, for all I know. The good thing about it being an ex-DCX corporate vehicle is that I KNOW it was cared for. If you were an employee in the company car program, you were *required* to service it at a specific location in Auburn Hills, which is not a dealership (I used to work at DCX HQ). If you didn't follow the maintenance schedule, the car could be taken from you and you could be removed from the car program.

[Fiveoh]

as a matter of fact, there is:

TSB 09-005-05 dated dec/2/05

SUBJECT:

Multiple Cylinder Misfire Or Rough Idle

OVERVIEW:

This bulletin involves rotating all engine exhaust valves, decarbonizing the combustion chamber.

MODELS:

2004 - 2006 (CS) Pacifica

2005 - 2006 (LX) Chrysler 300/Magnum/Charger

NOTE: This bulletin applies to all CS vehicles built after February 1, 2004 (MDH

0201XX) equipped with a 3.5L engine (Sales Code EGN).

NOTE: This bulletin applies to all LX vehicles equipped with a 3.5L engine (sales code EGG).

SYMPTOM/CONDITION:

The customer may experience occasional engine misfire during certain vehicle operating conditions.

A MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 - Multiple Cylinder Misfire. Various single cylinder misfire DTC's may also be present. If the frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in “Limp-In” mode.

The misfire condition may be caused by one or more engine exhaust valves that are slow to close. Late closure of an exhaust valve may be the result of no valve rotation and the associated build up of carbon on the exhaust valve stem.

Thanks dude, gonna keep this thread on file just in case.

[COLORADOMAGNUM]

Thanks for the info, Fnky. No problems with my 3.5 yet, but good to know about this.

[l1tech]

you guys are too quick with the clubs and pitchforks. although i haven't heard of this happening on an LX yet, this problem has plagued 3.5L and 4.0L engines for the last eight years or so. weak or out of spec valve springs are the cause of carbon build-up on the exhaust valve stems, resulting in misfires.

here are excerpts from TSBs:

TSB 09-002-03
SUBJECT:
Engine Stumble/Misfire - MIL Illumination
OVERVIEW:
This bulletin involves decarbonizing the combustion chamber and installing
new exhaust valve springs.
MODELS:
1998 - 2004 (LH) 300M/Concorde/Intrepid/LHS
1999 - 2002 (PR) Prowler
NOTE: THIS BULLETIN APPLIES TO VEHICLES BUILT PRIOR TO APRIL
1, 2003 (MDH 0401XX) EQUIPPED WITH A 3.2L OR 3.5L ENGINE (SALES
CODES EGC, EGE, EGG, EGJ, EGK, EGW)
SYMPTOM/CONDITION:
Engine stumble and/or misfire. More noticeable during a light throttle tip-in or when
transaxle goes into lockup (approximately 47 m.p.h.). MIL illumination with Diagnostic
Trouble Codes (DTCs) P0300 through P0306, individual or multiple cylinder misfire.

TSB 09-003-03
SUBJECT:
4.0L Multiple Cylinder Misfire
OVERVIEW:
This bulletin involves inspection of all engine exhaust valves and a decarbonizing
procedure if necessary.
MODELS:
1999 - 2004 (WJ) Grand Cherokee (All Markets)
2001 - 2004 (WG) Grand Cherokee (International Markets)
1999 - 2004 (TJ) Wrangler
1999 - 2001 (XJ) Cherokee
NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A
4.0L ENGINE (SALES CODE = ERH).
SYMPTOM/CONDITION:
The customer may experience an incident of engine misfire during certain vehicle
operating conditons. The misfire may occur when the vehicle is operated between
80 - 112 KPH (50 - 70 MPH) and under light loading conditions, e.g. slight uphill
road grades. This condition may occur at all ambient conditions, but is more
noticeable when ambient conditons are less than 0 C (32 F).
If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also
have occurred due to Diagnostic Trouble Code (DTC) P0300 - Mulitiple Cylinder Misfire.
Various single cylinder misfire DTC’s may also be present. If the frequency of misfire is
high the Powertrain Control Module (PCM) may place the engine in “Limp-In” mode.
The misfire condition may be caused by one or more engine exhaust valves that are
slow to close. Late closure of an exhaust valve may be the result of no valve rotation
and associated build up of carbon on the exhaust valve stem.

I just had this very same problem on a Jeep with a 4.0L today that another shop diagnosed as a burnt valve. It is a more common occurance than you may think.

[MooNDoGGie]

I wish I would have had knowledge of this crap before I bought the 3.5L (crap design) engine. If I had I would have opted for the hemi!

Damn! Who puts engines in vehicles that have the same (incredible) problem for the past 5 years!

I'm pissed about this!