low throttle misfire

[Nerass]

I've been chasing a low throttle command misfire for quite some time. When i'm barely on it the car misfires and at idle it misfires but once I'm driving normal it feels perfectly fine.

sometimes i get a "random cylinder" p0300 code but there's no rhyme or reason for when it comes up and it never gives me a specific cylinder. i've run a crank relearn and it's been something i've been chasing for a while now.

any ideas where to start?

cobra jet - mono blade - pmas maf -ngk 555 - oem coils

when on the dyno my tuner didn't see anything out of the ordinary - so we think it's coil / electrical related. wouldn't that cause a hard fault/code?

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[usgiorgi]

It's probably your intake manifold runner control valves being broken or just not working. Very common failure on S550s. They replaced the intake manifold for me under warranty and that fixed it.
The codes associated with it are usually p0300 and p0308. It only happens when you're very lightly applying the throttle around 1900-2200 rpm.

 

[Nerass]

no imrc's because cobra jet

 

[usgiorgi]

Sorry, missed that part.

 

[Nerass]

anyone familiar with symptoms of a possible damaged/bad crank trigger wheel?

repeat i am not getting any codes..

 

[Nerass]

update... fixed it

the TPS sensor was resting ontop of the heater hose... i bent the hardline back a little and i'm no longer misfiring!!!!!!!

 

[Nerass]

just kidding.. this keeps returning. pulling my hair out chasing this shit lol

 

[Nerass]

update... p0316 p0300 are confirmed codes but do not seem to pop every time
i'm able to feel the misfire between 2300 - 3000

would a bad coil necessarily throw a code for the specific cylinder? is it possible multiple have gone bad? not looking forward to shelling out 300+ for a "possible" solution

 

[Chainsaw]

A random misfire code usually means the air/fuel mixture is running lean. But the cause might be anything from a hard-to-find vacuum leak, a cracked intake manifold, to dirty fuel injectors, low fuel pressure, a weak ignition coil, or compression problems. A dirty MAF sensor can cause a lean code and/or misfire to occur. You need to go through the process of elimination to find the source of the problem.

 

[Nerass]

swapped with another set of coils, issue persists
reinstalled intake manifold with new gaskets issue persists
went to 47 lb injectors with supplied tune issue persists
soldered my y-harness for the throttle body again - issue persists
reflashed my tune a few times - issue persists
installed a new set of ngk 6510 with out of the box gapping - issue persists

i am not throwing any codes for the MAF, or any other sensors
i am seeing misfire counts on ALL cylinders - some more than others - is this an indication of bad coils or something larger.. i did not see a difference when swapping coils around.

https://datazap.me/u/nerass/2-3-pull-wot?log=0&data=1

misfire is really only felt between 2k and 3k but i can hear it at idle and the counts continue to go up. rarely does it throw a code, but eventually will and it will give me a p0308

 

[Eric Benson]

Would it be possible that something is not correct with your valve train. I had a similar low throttle hesitation (flashing check engine light due to misfire). The diagnosis was one the solenoids in the valvetrain that advances/retards the cam position was not putting out enough pressure. Therefore the valve timing was not where the computer thought it should be and most likely created a lean condition. The situation corrected itself if I got on the gas.

 

[Nerass]

Would I be able to determine this if I log a particular pid? I don’t get a flashing CEL

 

[Eric Benson]

I don’t think so. It was originally getting a bad cam sensor but after it was replaced the cel went away. The diagnostic was done by the dealer after they consulted with ford tech center for a week. But as far as I understand they tested the Solinoid presssire and it was out of spec. Maybe mine was just a one off failure of that part.

 

[HeavyHittersMaryland]

I have the same issue, did you ever figure anything out?

 

[Nerass]

I have the same issue, did you ever figure anything out?

strange enough it was my tune.
my new tuner ( rob @ palm beach ) suggested in a very dumbed down version, it was related to the idle.

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