SROC276

Thanks in advance to any input on this situation. I have pm a few but figured to gain additional input.

Since December 1st I've gotten 3 misfire episodes where the engine shook violently and ther was a blinking cel. All 3 events had p0300, 301, 302, 303, 305 and 306. I cleared the codes for two event. The 3rd event just required a shut off and restart and cel cleared.

No issues on highway cruising or daily driving. Happens 100% time on start up only. O2 sensors and plugs both replaced and under 1 yr old. Car has 46k miles, tune and factory row boxes. Valve buckets replaced 3 months ago and no issues.

Car went into dealer for oil change and problem started happening right after.

Thought?

abcut973

pm replied.
When you say the valve bucket you mean the cylinder valves have all been changed?

SROC276

Not sure the valve buckets? Weistec sells the Sls ones, I got the newer improved ones according to the tech. They have an anti friction coating now on them apparently. It fixed my valve chatter that I had prior from the heads.

roadtalontsi

my only thoughts are a failing fuel pump check valve, allowing fuel to drain back into the tank and air in the fuel rail. Go to start and it misfires temporarily, once misfires are detected it shuts the fuel injector off for that cylinder. Go to restart the car again and the rail has bled by that point. what cylinders are the codes for 1,2,3,5,6? all cylinders furthest away from where the fuel line connects to the rail. Does it only happen after the has sat over a long period of time?

SROC276

Interesting yes....only occurs at start up...not when cruising or wot. Usually (3x in last 3 weeks) happens when car is parked for up to 1hr...once I start it, I'll notice an initial shudder, bad idle then it starts shaking. I switch it off, then on and all is good or when I clear using my ob2. I have noticed slightly rough idling too now.

SROC276

sOLVED!!!

You are the winner! Fcv was bad after they tested the pressures. They ordered parts and will replace it under warranty! Much thanks!

SROC276

Guess it's not solved....fuel check valve changed....after 400 miles, occurred again.....my tech checked fuel pumps and found out pressure was bad so replaced it......500 miles later....same issue again this morning only. Shut off car and restart and everything clear...seems to be quite random...cel did not stay on this time...bad fuel?

Cold Start up idle also different...not as high of an rpm like normal. Would fluctuate a little...thought it was going to happen again...occurred a few hours later upon start up.

Petakii63

Intake manifold leak most likely. Bad gas is wishful thinking

abcut973

Intake manifold gasket would generate a lean condition in most cases therefore P1071 code thrown. Which is not the case here.
As well idle would be louder/higher in rpm with an intake leak.

Petakii63

Yes but he's also misfiring and it could be from a leak and the car maybe running leaner. So he check the plugs. O2 sensors. Fuel system. Possiblity could be bad coilpack & or wires. Op also check the crankcase breather hose, those tend to crack from the intense heat and could cause a odd idle and in rare cases CEL.

SROC276

Yea. A lot of work done to the car in the last yr....fuel check valves fuel pump, intake gaskets, O2 sensors, plugs all replaced in the last yr. thinking coil pack issue but not sure at this time. Could be bad injector as well...those are the only two things not checked...again not sure...have 2 weeks before warranty runs out so will set an appointment soon.

Petakii63

How many miles on your car? Any mods?

w204nyc

Thats crazy because its the same problem I'm having. All but cylinder 8 were misfiring. I had all coils and spark plugs replaced. Changed the fuel pressure sensors as well. All codes cleared abd after 309 miles another CEL. Going to see what it is tomorrow!

SROC276

I have about 46K miles on the clock, mods are oetune, shorty header, exhaust IPE, ROW air boxes and AFE filter....that's it mainly for the engine.Everything has been on the car for at least 2 yrs..

SROC276

Yes I had multiple cylinder misfires recorded....not sure but so far, injectors were checked, fuel, filter and pump changed....coils and plugs are the only two things now I am thinking about....let me know what you find..email is zvg888@gmail.com

Petakii63

Call Jeremy he knows this car In and out. Another thing could be a leak in the header... What headers are they?

SROC276

Yes I've already emailed him to ask. He mentioned to review several things which we have gone over in the past. I checked header and it's clear...I am running the renntech shorty....if cracked would normally cause a lean condition too long side misfire which I don't have. This seems to be completely random. The flashing cel every time it occurs is what worries me most.

w204nyc

My dealership just ran the codes again and it's O2 sensors acting up. They keep recommending that I change the whole exhaust but I think they're just doing that to get money out of it

SROC276

Tell them mine were both changed and I am still seeing these events....went to a different shop today and they told me that a client of their with a brabus car does the same thing from time to time. They suspect it's vapor lock which is where fuel fumes build up in fuel rail and don't necessarily bleed out. I changed my fuel check valve to fix this but still have it.mguessing it's a random issue.

SROC276

Haven't thrown a code recently but happened again. Re-read your post and yes the last codes on the cel were for cylinder 12356, furthest away from fuel line. I am running headers so no heat shield..mb has notified my tech regarding misfiring issues due to winter blend gas here in California and hotter temps. Since fcv, pumps are all new units....I am thinking main wire meshed fuel line exposed to header is heating the winter blend to a point to cause vapor lock? I've touche that line before and it is hot as hell after a spirited run. Thinking of wrapping it in thermal tape and see if any changes. Thoughts? Or because it's occuring there at 12356, focus on heat shielding the fuel lines there.

I don't have any issues with summer blend fuel.

SROC276

Update:

I switched gas and I am now using Chevron vs 76. Thinking maybe has caused my issue. So far 1 full tank and no misfire at start....but cold start is not as crisp or idle as high as it used too. My cold start is now 1k rpm vs 1.3-1.4k idle at first and lumpy like it is running rich? Also hearing this flapping sound initially then everything idles perfectly and sound disappears?
No check light. Power is good and no other known issues....weird.

Thoughts? How do I kill these gremlins?

abcut973

1kRPM at cold start is normal. It should settle down to 500 after 30s.
You are saying yours goes up to 1.3k? There is definitely something if it is the case.
As for the sound isn't that the usual dry lifters?

rentzington

yeah, if its a tapping sound that's what it is.
Mine does it and i freaked out at first and researched and its pretty much normal.

SROC276

Update: I am in my 3 full tank of Chevron Gas here in California and the misfire issues have stopped completely. I was at the time using 76 gas which I was told by several shops that it had a higher ethanol content for winter blend vs other gas brands. My car apperently did not like it and would occasionally suffer from vapor lock as I am told. The v12 benzs have had a similar issue according to the dealer as well. In any case....just wanted to share in case other folks experienced this...perhaps empty out the old and switch it out.