DRW21

Sorry for the novel but this is not an easy one to get sorted. I am here asking an engine guru’s for help.

My car is a 2009 GT auto, it’s my first V8. I am sure the misfire issue was there when I bought it bit I didn’t realize at the time.

At that stage there was only 32000 miles on the clock.

The symptom I am have difficulty sorting is………….

A small vibration from the engine from 900 up to 2500 rpm. After 2500 the engine runs very smooth. No odd noises just the ticking of the injectors.

While driving the car gently no issue is felt but you can hear a light popping sound from the pipes.

When driven with some gusto the misfire sound is not as noticeable but it does lack some power below 2500, after that she pulls great.

The engine is stock apart from the plugs and it has Flowmaster axle backs, the exhaust drone is very noticeable from inside the cabin at highway speeds.

No engine light and no codes to clear unless I unplug things like sensors and injectors etc.

You can see and feel the engine shake lightly from idle up to 2500 rpm.

At idle there is a hint of the vibration and it slowly gets worse as the revs are increased, once the revs get to 2500 rpm, then the engine runs perfectly smooth.
Even if the revs are increased gradually while in neutral or driving with a heavy foot, beyond 2500 no issue can be noticed.

When I drive car with both VCT solenoids unplugged I get the expected P0010 and P0020 codes and the misfire is the same.

What has been done to seek cause of issue so far.

Fitted new NGK iridium plugs, more grunt but still the same misfire. Awesome plugs!

Unplugged the injectors and cop’s one by one at idle and also at 1800 rpm and each item makes a difference to the revs when unplugged.

Cleaned the MAF sensor and throttle body. Checked for air leaks. None found.

All cylinders compression tested, all even at 185 psi.

VCT solenoids were stripped and cleaned and are both working fine.

Checked every lash adjuster and they too are in perfect order. I have turned the engine over with the cam covers off and there is good oil flow everywhere.

Cam phasers didn’t sound bad but I stripped them to check for any damage, nothing found.

Timing cover off to check timing, found both timing chain tensioners had blown the factory seals. New Felpro seals and the timing was set correctly. I thought finally I had found the cause of it.

The engine did run different after the seals were replaced. A bit more power down low and less exhaust drone but the misfire was still there and seemed to be the same.

The injectors have been flushed and tested and they all flow perfectly even. New fuel filter fitted.
Here’s where it gets odd, I fitted a new JLT3 cold intake with its tune and the misfire sounds a bit more pronounced, that tells me it could be fuel related but it’s all been checked.

Can anyone be of assistance by telling me what to check next?

Thank You for our help – Dave.

Cavero

I'm not a guru, but most of what I would have thought to check you already did. Just to double check, you know it's misfiring from feel, or from the misfire count in the ECU? Or both?

It sounds like you're probably been seeing this for more than one tank, so bad gas is probably ruled out.

DRW21

Thanks Cavero, the misfire has been there for a ages, just started to get to it lately. No misfire codes from the ECU at all.
Cheers

houtex

I don't have anything to add, honestly. I mean, it looks like you've done everything except hook up a Ford scanner (or equivalent) that'll show you the misfire count live.

Here's a video from FordTechMakuLoco that explains what I'm talking about, see below. His videos are very 5.4 specific as he works on those more than the 4.6. Just the way it is. But a LOT of the 5.4 stuff is almost directly translateable to the 4.6 in our cars. You can also look at this search for 'misfires' and watch his stuff on all the ways a misfire can be found/dealt with/what is:
https://www.youtube.com/user/FordTec...?query=misfire

I did want to say this, though:


This information has been noted and will be possibly enacted upon with Awesome, even with 180K+ miles. I bet she'll like 'em. Thanks for that! Here the video, and I hope that helps!

DRW21

Thank You for that info Houtex.
I'll dig deeper.