Hey Tom L. IAC didn't fix it (Code 43)

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Any idea what to try next? Cleaning, then replacing the IAC didn't phase the problem, P0307 literally within 2-3 miles of clearing it but -ALWAYS- occurring at low RPM.
If I clear the code and then watch my RPMs close, kick it into neutral before coming to a stop and maintain idle above 1000 rpm it won't occur and the truck runs smooth as silk all day long.
I'm about ready to take it to the dealer, but am hesitant to at this point because I'm afraid they may want to re-do everything we've already done and charge accordingly.
Thinking more about this, in retrospect I honestly believe this problem, all the way back 18 months or so when it initially started may have always been occurring at low RPMs, but I didn't pick up on that until we SAW it doing it in the shop a few weeks ago.
I'm also beginning to question now if when I swapped injectors if there's a chance I mabye got 'em mixed up and put them back the same way they came out. (Dyslexia runs in the family) So I guess the question here would be if it is at all possible for this to be an injector problem yet only show up at low idle?
Thanks!!
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Possible, but the fact that the engine dies unless you give it a little throttle indicates a bigger problem than just a single cylinder. All else being equal, a V8 can drop a cylinder and still maintain an idle (albeit a rough one), even under a bit of load. At this point, an in-depth analysis of the entire FI system is needed (a scanner capable of displaying real-time stats from all the various sensors) to find out what's out of whack. This is a job for a professional. I understand the reluctance to give the dealer carte-blanche to run up a big diagnostic bill, re-doing things you've already done, but at this point, I don't think you have much of an option.
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Misunderstanding!!!
No, it doesn't die. Never has. It runs fine. It simply "codes" if I allow the RPMs to drop below 8~900, as when decel from 30 mph down to a stop. The truck idles fine, even in gear, albeit it slightly uneven once the P0307 gets stored. But even with a code stored it doesn't die nor does it even act like it wants to.
I know I cannot take it to the dealership and tell them what not to do. However, I think I owe it to myself (and my checkbook) to at least give them an itemization of the things we have already tried along with a precise description of the symptoms. Maybe that way they won't try to shotgun it and will actually look a little harder for the cause.

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writes:

Before I would do anything else, I would "try" cleaning the combustion chambers with Mopar Combustion Chamber Cleaner. I have seen several times where excess carbon builds up in the combustion chamber and valves and allows the engine to run lean enough for the PCM to pickup a cylinder misfire code. This is a cheap solution, if it works. Just follow the directions on the can and leave it soak for as long as possible. I think the directions say a minimum of two hours, longer is better and overnite is ideal. Then run the s**t out of it to blow the carbon out. It will smoke like the dickens so don't do this in an enclosed area. If this doesn't work, then you probably have no recourse but to see a dealer. Explain to the service advisor/service manager what you have done in detail and ask that he put his best driveability tech on the job.
Good Luck!
Mike

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Thanks Mike & Tom.
So from what I think I hear you saying is this is unlikely to be an injector problem? (I ask because I'm having nightmares about the injector swap we did several months back, thinking now of the possibility I might have accidently put the original injectors right back into the same holes 5 & 7 rather than swap them). If based on symptoms (occuring at low RPM only) there's still a chance of this being an injector problem, say so and I'll try that.
I had another guy try to tell me it could be a #7 cylinder problem and suggested a possible ring, valve or head gasket problem. I mentioned we had run a compression check and all cyls were 133 or above; wouldn't a good comp check pretty much rule out rings, valves or gasket? There's no foreign fluids in either the oil or water. Thanks
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Pretty much, yes. There's still a whole host of things that 'could' be wrong... the combustion chamber could be carboned up... it could be a weak fuel pump... it could be a failing cam position sensor... it could be... you see where I'm going.
Do the combustion chamber cleaning. If no good, and for your peace of mind, swap the injectors again (put a little dab of paint or something on #5 [cause it's easier to reach] before removing it, just to be sure you get them swapped) - it's easy enough to do. Doubtful it will change anything, but what the hell...
Beyond that, I think you need to get it to someone with more advanced diagnostic equipment.
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I haven't followed the thread with the intensity that I should have, but IIRC, the misfire code is the same cylinder each time, right? If so, the injector swap (if done properly ;^)) should eliminate that possibility. I would think that if the code was persistent to one specific cylinder it is likely not a cam sensor or fuel pump since they are common to all the cylinders and would probably generate a random cylinder code... but hey, I been wrong (many times!) before. Give the CC cleaner a shot and report back... just remember, soak it as long as you can!
Mike

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Right, P0307 every time. More detailed symptoms (finally) we have ascertained that the misfire code is occurring only at low rpm, decelerating from 25~30 mph down to a stop and/or idling in gear as at a stoplight. Idling in gear it will spit out a misfire code almost immediately. Always P0307.
However, clear the code and thereafter maintain a high idle above 1000 rpm (requiring you to throw it into neutral when approaching a stop) and the misfire code will NOT occur. Freeway speeds are trouble-free.
Engine does not stall.
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Mike Simmons wrote:

Is combustion chamber cleaner something I should apply to my truck engine "every now and then" even if it runs fine?
My '98 1500 has 135K miles on it right now. Has no problems running; starts up fine and I still get about what I got in mpg when it was new.
I use throttle body/carb cleaner and "fuel system cleaner" usually every other [3000 mile] oil change, but was wondering if the CC cleaner was something that could be done as well to keep things running optimally.
Or is CC cleaner a rather "traumatic" treatment to be used rarely when something seems to actually be wrong with the engine?
SMH
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Stephen:
The Mopar CC cleaner will not hurt a healthy engine and is not traumatic in any way, but if you are not experiencing any probs, why go to the expense? Some of the better fuel injector cleaners have the same chemicals in them that is in the Mopar CC cleaner. The best FI cleaners IMHO are 1.) Mopar FI Cleaner, 2.) Chevron Techron, 3.) Valvoline SynTech. In fact, these are the only ones I would recommend. They are slightly more expensive that some other brands but they are better. I think Tom L. will agree with this... let's see.
Mike

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As long as we agree that that list is in no particular order, then sure :)
I run a bottle of Techron through my V10 every 5-6K miles or so... seems to keep things from gumming up. One of these days, I'm going to buy me one of those lighted borescopes, then I'll see if I need to run any CC cleaner through my engine.
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Agreed... in fact, I "think" Chevron makes the stuff for both Mopar and Valvoline.
Mike

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Mike Simmons wrote:

Thanks Mike.
I currently pour in some of the Techron every oil change, so it seems that should be more than sufficient.
What a great truck! Of course, it now costs me $100+ to fill up, so maybe some solar panels and some wind generators all over the cap and hood to run a washing machine motor hooked up to the drive shaft could help me out.
Home brew hybrid and serious public fire hazard!
SMH
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Yeah, those $100 fillups ain't fun are they? Wouldn't you know it, I'm leaving next week for a 2000+ mile trip towing my RV... guess I be on a first name basis with Messrs Mobil, Shell, BP, Citgo et al.... hope they don't want a co-signer ;^)!
Mike

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We'll accept your shiny new FEMA debit card here in Texas ;-)
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We are out of them in Houston, think the illegals came in and took em all.
writes:

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Thanks Tom. I'll look for the CC cleaner tomorrow. I'm sure the dealer would have it, but they're a little off my beaten trail. Hoping to maybe find it at Autozone, Pep Boys or O'Reilly.
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You need to get this from the dealership... I haven't seen this in any 'aftermarket' form, and if it did exist, I'd trust the stuff in the Mopar can more. I don't usually say this, but having used the stuff first-hand, I know what it will do.
The instructions you found are correct, but I'd add one more step:
8) Change your spark plugs
The CC cleaner will foul them pretty badly - and a set of plugs are cheap.
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Amen! I'm not trying to schlep Mopar stuff on the NG, but this is the only product that I've known to really work as advertised... most of the other stuff out there is snake oil.
Mike

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[insert generic rant about over-priced, re-labelled Mopar parts here]
But yeah - the CC cleaner is an exception to the above-referenced rule :)
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