Misfire under load (High RPM)
 

I bought my car about a month ago. It ran great the entire time, up until about last week. I was driving and my MIL started blinking then went solid. Knowing that is a sign of a type A misfire, I pulled over, and key cycled the car and cruised home at low RPMs. The light stayed on of course, but I did not cause any additional misfires.

I used my Bluetooth Actron OBDII Scanner (Best 70 bucks you can spend), and these were the codes.

P 0303 - Cylinder 3 Misfire Detected
P 0308 - Cylinder 8 Misfire Detected
P 0300 - Random - Multiple Misfire Detected

It seems to idle fine, maybe there is a slight misfire, nothing too noticeable though. So anyway, I cleared the codes with the app on my phone (Awesome!). Then I began troubleshooting. The car will only misfire under high engine load, High RPMs, etc. Usually around 4-5 thousand RPMs, the light will blink, then go solid. The ECU disables those 2 cylinders in order to prevent damage to the cat. I cleared the codes, and have just been driving normal (to other people's standards). It has been about a week without the light coming back on. But I cant enjoy any prolonged acceleration pulls, and its just frustrating.

I'm not sure if I should change the plugs, or coil packs. I already cleaned the MAF, and that is not the issue. But would two coil packs go bad at the same time? I'm not sure what to make of this.

Advice? Experiences?

Much appreciated,
Danny

Try swapping the ignition coils on those cylinder to two other to see if it stays with the cylinder or coil. If it stays with the coils, then replace them. If not, then swap the same set of plug wires. And if it still stays with the cylinders, try the plugs. If it's still localized to the cylinders, then it could be defective knock sensors or problems with the cats.

I've been meaning to do that. I just didn't bother because I found it to be pretty strange that two coil packs would go bad at the same time. I'll try it out when I get home in a few hours and I'll get back to you.

I will update this thread tomorrow. I bought a fuel filter and I have a friend putting it in for me tomorrow, and I will go from there.

Ok so I bought a FF868DL Fuel Filter. We looked under the car (under the plastics) and in both plates under the back seat. Where the hell is the fuel filter? lmao

On a side note, I am only reading a cylinder 8 misfire now.

For the V8, the fuel filter is integrated into the sender unit, inside of the left side of tank. You have to replace the sender.

That makes me believe it isn't the problem. How often do they go bad?

Also, I find it weird that only cylinder 8 is misfiring now.

Really don't know where to go from here.

Actually, the fuel filter is scheduled for replacement at 65,000 miles. It's $260 at parts.com.

UPDATE
 

Ok, I changed all 16 plugs (pain in the ass) and I found a small hard vacuum line with a slice in it, and replaced that too.

The car was running OK, no misfires in sight.

It has been about a week now, and just this morning, the SAME codes came back!

What could this be?

Have you tried swapping coils to see if the error stays with one particular coil? If it stays with the cylinder, then try swapping plug wires.

Did you find the problem on your car Danny06191? Had a similar issue with that I solved eventually.

No, I have not found the issue yet. Cylinder 8 is the only code that is being thrown right now.

I have recently replaced fuel injectors, as well as all the plug wires, with no luck.

Right around 5thousand RPMs, the light comes on and it reads for a cylinder 8 misfire.


What did you to to solve your issue?

misfire.
 

The ignition coils are 2 phase after 4000 rpms if the engine senses a flaw in combustion it shuts that cylinder down until you cut the car off and start it again for the computer to register the problem again. If the ignition coil has been replaced then your problem is the EGR valve. I learned the hard way. I have all AMG mercedes,but they are all the same scenarios. Good luck I hope the helps.

What do you mean by 2 phase? I have swapped coils in the past, while troubleshooting, ended up getting the same code so switched back. However. It is possible that while I switched them, it threw the code from memory and the coil did not fault, because the misfire is intermittent. I will be looking into coils. The EGR valve wouldnt effect only one cylinder would it?

The only code that is being thrown now is cylinder 8, I just tried 3 extra coils a friend had and they all didn't help. Not the coil, changed the plugs, wires, and injectors. Corrected cylinder 3 it seems, but now I am left with cylinder 8. Have a bottle of techron in it now. Oil change tomorrow. Idk what else to do. Why would an egr valve throw a cylinder 8 code only?

Also noticed it will not misfire in first gear*

misfire.
 

It was hard to understand when it happened to me. I installed a supercharger on 1 of my w210 e55 and deleting the EGR is what caused my cylinder 3/8 misfire, But the EGR valve gets clogged up where it goes into the intake and throws a misfire. Also just because the code says cylinder 8 does not mean it's exactly that it can also mean it's a supporting cylinder. There are alot of ways to get a misfire code but if everything else was done to perfection then I would really look at the EGR valve. You don't have to replace it just clean the pipe that enters the intake manifold. Good luck I hope it works out.

Update:

I have now noticed a weird burping noise coming from my throttle body as well.

Here is a video link that might work.
https://drive.google.com/file/d/0B0R...it?usp=sharing

What grade of gas are you using?

The sound in the video is more like something is loose, like a bad pulley or some other rotating part of the engine.

NEW Details
 

Guys I have noticed something recently. After running fine for a few days, it began misfiring again with the light blinking then going solid. I began doing some scenarios for testing.

If I am cruising down the road, and put it in neutral.. I am able to REDLINE the motor and it will NOT misfire.

But, as soon as I put it in gear, it will misfire right around 4000 rpms.

^^ That has to be a huge hint. But I'm not sure what that would suggest besides it is only under load. Would that be a fuel pump issue? The dealer did keep telling me it was failing the injector test. But I replaced them, maybe they aren't getting enough pressure under high load?

Fuel pressure regulator? Pump? How can I test them seperately?

Das star
 

Do you have access to das star?
A nec tool for troubleshoot these cars.

I might inclined to try another mass air meter.

Be sure to use only genuine Bosch.

With das star you can read fuel trims while driving, you can function test injectors etc..,,,

Did you check compression in #8 hole?

How do the plugs look in that hole?

Is the car down on power?

How mlg?

Be patient. There is nothingagicabout these cars..... Just a fuel inj v8 with high priced parts svc. :))

I do not have access to star. I do have a live datastreaming obd2 reader. But I'm not sure what I'm looking at.

But here is some live data while driving:


https://cimg4.ibsrv.net/gimg/www.mbw...f2082a2b71.png


https://cimg5.ibsrv.net/gimg/www.mbw...323e01ddb8.png


https://cimg6.ibsrv.net/gimg/www.mbw...aa6552cd32.png

After I throw a CEL this is how it looks.

https://cimg4.ibsrv.net/gimg/www.mbw...18ae2c8e7c.png

Freeze Frame data:
Code P0300
Abslt TPS 38%
Enging RPM 4300
Calc Load 74.1%
MAF 73.39lb/M
MAP 22.7"HG
Coolant 183
IAT 66DEGF
IGN ADV -28.5 DEG
Second Air Atmospheric
ST FTRM1 0%
ST FTRM2 0%
LT FTRM1 8.6%
LT FTRM2 7.8%
Veh Speed 84MPH
Fuel Sys 1 Open-Drive
Fuel Sys 2 Open-Drive

***HUGE UPDATE***
 

So, a couple of days ago my car would not start. Ironically, I got really happy because I now had new symptoms to chase down this issue. I figured it may be a faulty crankshaft sensor, and they are cheap, and known issues, so I replaced that, still nothing. So I checked a few things.

-Checked for spark. Got it.
-Checked fuel pressure at the valve on the fuel rail. Nothing!
-Checked fuel pump fuse. Good.
-Checked fuel pump relay with a miltimeter, 70ohms. Perfect.
-Checked voltage at the sender unit under the backseat, ~11 volts while cranking. Nice.

The pump and sender made no noise.

The next day I tried to start the car and I could hear the pump turn in and whirl. Car started right up.

I ordered the sender unit(driver side) as well as the pump on the passenger side. They come in tomorrow.

I can't wait to get this issue fixed! So many new parts, and nothing but smooth driving from here on out hopefully. I will update when fixed.

Did you happen to solve the misfire? I am having the same issue.

DodgeDan!
 

Yes I did fix my issue. The last update I posted on this thread said that I had replaced the fuel pump and sender and that I would get back to the thread with results. Sorry, I forgot!

The pump was bad. But I still had my misfire codes.

The REAL FIX was determined later that week.

COIL PACKS

I really had nothing else it could have been after replacing a lot of **** (that needed to be done anyway).

I pulled all 8 coil packs off and replaced them with 8 new coil packs a friend had laying around.

Upon further inspecting my old ones, I found that 6 of them had cracks in them. Similar to what benzing had said earlier in this thread, the coil packs are 2 phase after 4000RPM. The swapping coil packs with other coil packs method was useless because most of them were cracked. Also, even though it is telling you certain cylinders. I wouldnt trust it entirely. It seems to me that in some cases the ECU will throw random cylinders, and sometimes not correct, or not all effected cylinders.

Anyway... I'll bet my left nut, if you replace all the coil packs, your misfire will go away. If you wanna explain the situation a little bit better, you can email me kreck.daniel@gmail.com

Good luck!