Missfire only when accelerating quickly past 7k rpm.
 

Just as the title suggests, when its a gradual acceleration to redline i haven't noticed a problem, however gunning it always gives me a flashing CEL for about 5 seconds then it goes away. This has happened since i bought the car about 8 months ago :banghead:

Things i have already done:
-read the "SUFFERING FROM A MISSFIRE START HERE" post.. several times
-BHR ignition (with wires) with NGK iridium plugs
-cleaned ESS (did not perform the 20 break stomp though)
-cleaned MAF
-replaced small ~6" hose under the trunk of air filter box because of a tear
-cleaned accordion
-cleaned throttle body
-smog was done and passed around february so i do not believe the CAT is bad (no rattles within the housing either)

Things to note:
-04 MT engine has roughly 180k miles on this engine/ about 202k on the car
-only use premium at shell or chevron
-fuel gauge stops working at around half a tank (i hardly ever let it run lower than half anyway, however since the sensor and pump are in the same housing i think it could be a problem)
-seem to be running pretty rich
-have not tried to clean fuel injectors yet

:) Any help is greatly appreciated, comments and questions also welcome. I have been putting off getting the fuel pump checked since most of the stuff I have done already I did/installed myself to save money. If i have left anything out please let me know I will be checking the post regularly. Oh and be gentle.

*thought i should add that since i noticed it misfire in my first attempt to redline months back, i strictly kept the car under 5.5krpm, the only reason it started was because i thought maybe after putting the BHR kit the problem would be fixed. I again am keeping it below 6k rpm to avoid a misfire, and have only attempted it a few times after each thing i have tried fixing.

I'm getting something similar, but at 5-6k. I'm fairly confident that it's the cat going out.

In all honesty it could be, I have been trying to check off all the least expensive things before going to a stealership or another shop to get it inspected. I still feel a bit confident that the CAT is ok, BUT I am keeping an open mind and am willing to all suggestions.

If CAT is stinking hot, it could be bad. You can also pull it fairly easily and look. If the media is all broken up, it is not good. If the pass seat is getting hot, likely not good.

I would look at fuel pump. My guess is that the gunning it option is hard acceleration, while gradual does not have your foot to the floor. The closer your foot to the floor, the more fuel you need.

I you got that many miles from a fuel pump, frame it when you take it out. It is special.

180K engine and a comp test was not your first thing done because???

Would a failing fuel pump ever cause a very rich condition, like 10:1 or less?

Could it be due to carbon deposit.

if i drive my car after a week the first few times i red line the cell blinks, i'd sy after 3rd attempt cell goes away and she runs like a beauty.

Have your codes read and see if anything comes up..

I noticed you didn't state you cleared the memory with all the othe cleaning you did you could be pulling a false misfire and before any one says it's not possible to get a false misfire I have had the same thing happen to me. I forgot to plug the MAF back up it after my install of BHR coils and it caused a misfire that continued to recall till I simply cleared the memory with the 20 brake stomp.

low fuel pressure will force the ECU to compensate. It will try to richen the mixture, and will show high positive fuel trims. It will not be running rich, but the computer will think that it is up until the point where it cannot compensate, then it will set a code that you are running lean (because it cannot compensate any more).

I was new to automotive when I first purchased the vehicle, since then I have taken classes and having been working on this car and enjoying it. In fact now I am getting into the Chrysler CAP program at school :).


Ok so with what you have all told me (thank you all by the way), I am gearing towards either the fuel pump or the CAT. BUT i think the CAT may have been replaced before. When I got the car, i noticed a hole on the flooring material next to the seat behind the passenger (it is on the wall that seperates the two rear seats). Looking closer at it now, I noticed it was burned. The cables beneath the hole were replaced/reparied since, and it looks like this may be the cause of why my parking lights and lisence plate lights dont work (again, how it was when i got the car).

I have bought a Wifi OBD2 scanner and I have DashCommand on my phone for the codes and to just have an overall better idea of whats going on with the car. After using it these past few days I noted that it also gave me info about CO2 emissions and more than just the ability to look at/clear codes.

I would like to post a pictures of the burns and the info from the OBD2 sensor but I am unsure how. Again thank you all very much for your help :)

I am going to try this today, I will try to post my findings tonight. Im just worried that if my CAT is ok, continuing to missfire is just going to cause problems. Again I am not trying to race and I am not redlining every 5 minutes. I have only tried it after the repairs and once the first week i bought the car. But I do want to get it fixed and know if the problem was fixed, so do you think it would be ok or should i not risk missfiring?.

I tried redlining it after I installed the BHR kit several times, all yielding the same result. This is when i found out about it only happens when I am quickly climbing in speed. (and who wants to redline at a rate of 2 miles per second...)

Is there a difference between unplugging the battery and getting the codes cleared like through an OBD2 sensor? I know there are different types of RAM, I think the abttery clears NRAM, and the break clears KRAM (or something of the sort). Is the Keep alive memory where my problem would lie if it were just as simple fix as a break stomp?

p0302 flashing during acceleration.
 

I'm getting the same thing, only happens when my foot is in it, accelerating hard above 4-5k.
I've done the 20 brake stop and cleared using the OBD reader. I swapped the cat, now I'm really frustrated that didn't work... :banghead:

I have the coil mod done and replaced the back 2 coils in case one of the new ones was delivered bad. I swapped out the back 2 plug wires and changed all the spark plugs. Now, I'm stumped...

Stop wasting your money and get a comp test.

OK, so I learned something very important today. The cheap OBD thing does not reset the learned behaviors. I reset everything using my access port and the world changed. :)

The idle was instantly lower, the return to idle happened faster after pedaling, and it is running perfectly smooth.

To recap:
I was getting p0301 (happened once before at 30K, I now have 50K)
I had already changed the plugs, cleaned the esps, usual stuff, and narrowed it down to another bad coil (or two).
I did the coil mod d585's and put new plug wires in.
Instantly, I noticed that I couldn't here any more mis-fires and it was idling higher. I did the 20 brake stomp and reset the p0301 code using my cheap code reader.
The car felt like it was running great, but, on hard acceleration I got flashing p0302. Unlike before, I didn't get a mis-fire feeling...

I thought one of my brand new LS2 coils may have been flaky so I swapped out those 2. I also swapped those 2 plug wires just in case I buggered one when I put them together.

I got the same flashing p0302 even though the car felt good. When I had the initial p0301 at 29k miles, the cat got red hot and smelled like burning rubber. I thoroughly cooked the cat. At that time, I knocked the stuffing out of it and freed it up so I could drive while waiting for a new one to arrive.

So, this time, I put that "gutted" cat in just to eliminate that as a suspect and I really doubted that it was a problem. It didn't make any difference.

I hooked up my access port to see if it showed anything extra. I used it to reset everything, and problem solved!

The car launches better than new and I'm happy with the new coils. I even have 2 spares, and hopefully won't need them for quite a while. :lol2:

The 20 brak stomp would have done the same thing. My under standing is yes the batt disconnect will not clear the stored data and some how depending on what caused the misfire it will hold that misfire data and just give you a false misfire CEL this was my case. This is why it is important to clear all memory after such things as cleaning MAF,ESS and other such things so the ECS can learn the new correct data the clean parts are sending and not confuse it with bad data it has stored already giving you false codes.

I dont think the upgrades I have done/purchased can really be called a waste of money. And all I have realy spent money on was BHR ignition and MAF cleaner, along with a couple inches of vacume hose :). I figure if I can fix the problem by replacing things that need to be replaced anyways (such as the fuel pump) I can SAVE myself the $350 the stealership wants to charge me for a compression test. What are some symptoms of low compressino if you don't mind me asking?

Access port? Is it like a tuning device? (looks like a device used for reflashing?) So it sounds to me like it isn't something I can clear with the 20 break stomp if I am understanding correctly.

Also for those interested this is the cheap little OBD2 Wifi reader I am currently using, it isn't anything special but it gives me info on the fly.


In October when my classes start again, I will have access again to high-end scanners and tools which I will be able to use to do thourough scans.

I must have read your post wrong thought you said you cleared it with a AP. COBB ap is for tuning and much more trying to save up for one my self. As for signs of compression loss. Hard or no starting when engine is at running temp and as compression gets lower and lower it won't start cold. Misfires can be a sign loss of power higher fuel consumption constant flooding. Disconnecting the batt and doing the 20 stomp will set every thing back to factory as possible with out changing any flashes done. Allowing the ECU to relearn the engine and all the data comming in so if you disconnect the batt and do 20 stomp after you think you've fix your problem and your code continues then you truly have a problem that needs attention. If it dose not return then you've fix it.

The Cobb AP has all the basic OBD2 code reading/clearing functions too. You can clear codes there, just not reset the NVRAM

I wasn't sure if it would or not as I don't have one yet. I did know it can mask CELs like p0420 so the CEL will not light up but the code will still be there if you have the OBDII read. So the only way to clear the NVRAM is the 20 stomp.

Confusion on resets and what I did...
 

I've proven, by my own testing, that the 20 brake stomp does NOT do anything to the NVRAM. It only clears the KAM!

The odometer hold routine clears the NVRAM. The last part of changing MAPs, using the Cobb AP, will also clear it. It's obvious when you've done it properly, because the car re-learn's idle etc on start up after you've reset them both.

BTW, my compression is good, 50K on the car. You can't just use a compression gauge like other motors.

I apologize if my previous post confused some folks. Here is the procedures:

here are two reset procedures, one for the NVRAM and the other for the KAM. Neither will erase your radio presets and such like the method SpooledUp7 posted:

1) With the key in the off position, press and hold the odometer reset button and turn the key to on;
Continue to hold the odo button until the odometer reads "TEST" and then release.
2) Turn the key to off and repeat step one.

This will reset the entire PCM except the KAM which contains the sensor profiles amongst other things. You can reset it with the familiar procedure:

1) Turn the key to on
2) Depress the brake pedal rapidly 20 times in a row until the oil pressure gauge sweeps to halfway and back again.


I hope this helps. :)

Never done that or had to the batt and 20 stomp always work for me. I have red about the OD thing but allso red it didn't to anything but test your systems to see if they all responded.

Cobb AP and resets.
 

Changing, or reflashing the same map using the Cobb AP seems to reset everything in one step. The AP also has performance monitors. :)

I'm not trying to sell them, just saying it worked for me and butt dyno showed the results. :lol2: