Good Afternoon guys
I own a 2004 6MT coupe with no mods and a stock airbox (with K&N lifetime filter) and ive been having a strange issue as of late.
My car will intermittently generate a misfire/2 step burp sounding noise whenever i am accelerating with more than half throttle after 4.5k (sometimes it doesn't do it in 2nd but mostly in 3rd and above gears). I have played with the throttle input as I accelerate and it's definitely coming on right past half throttle (for example the car will still pull in sync with the amount of throttle input but only up UNTIL 4-4.5 when the noise/hesitation starts and if I let up slightly the car will still accelerate but with less power {per throttle amount})). I had a code for cam sensor come up about 2 months ago which I quickly replaced on the passenger side bank (which the code didn't show up until about 2 days after long crank issues which I knew it would because I have dealt with same symptoms on another G). The car still performs well and I have no other issues with power up until that RPM range. I pulled all spark plugs and they were fine and the coil packs were fine also. My air filter is quite dirty at the moment and it needs a cleaning and I plan on spraying my MAF sensor also to see if that will help. No exhaust leaks either. Only thing I have not checked is fuel injectors. Any help or guidance would be extremely appreciated. I have searched the forums extensively and have not quite been able to pinpoint someone with an issue of identical nature so I made this post. Thank You

 

Bump for visibility.

 

Clarification question du jour:

OEM or Hitachi sensor? Or aftermarket?

 

I'd scan for codes just to make sure there aren't any hidden ones. Then pull the spark plugs and thoroughly inspect them and the coil packs.

 

I believe it was replaced with the Hitachi sensor which is the OEM recommended brand. I know other cam sensors cause issues sometimes

 

True good advice. I pulled the plugs and coils. There was no fouling on the plugs and the electrodes appeared normal. No blistering on the coil packs and no springs missing from the coil pack boots. I did see a small bit of oil in a couple of the spark plug tubes.

 

I am almost certain its a cam sensor issue though now that you mention it

 

No hidden DTC's though? Usually when a cam sensor is intermittently failing the ECM logs that, try scanning right after you get it to stutter.

 

Check the throttle position sensor. It is a moving mechanical device, so it may have a dead spot or reduced output, but not enough to throw a code. Also clean the MAF. It is common for the MAF to get fouled when using air filters impregnated with oil.

 

where is the TPS located? I have gone about checking the coils and injectors and I replaced the valve cover gaskets that had a slight leak and still no change in this issue. The coil packs look dang near OEM and the spark plugs look fine also. I did replace a hose and the pcv valve that were looking bad and cracked and that hasn’t improved it. Interestingly enough when I put on a different air intake (pro tuning lab) the car ran a bit better and the sputter doesn’t happen till about 5k now strangely

 

Today I replaced a camshaft sensor in bank 2 due to throwing a code (sensor possibly went bad due to oil seeping into it from a bad valve cover gasket leak). Upon replacing the car seems to pull harder than previously (even before the sensor went bad) however still getting the sputter (at around 5k) and it seems to go away with slightly reduced throttle input.

 

@pyro90294 Hope you've found your solution

I had a multi/misfire at around 4.5k rpm that does not happen if acceleration conditions aren't WOT, and intermittently my warm idle would be a tad bouncy. I had recently done a lot of the things you list above (new air filter, cleaned maf and TB, new cam/crank sensor, new spark plugs, inspected/tested and replaced 2 coilpacks, which led to new valve covers, and 4 new o2 sensors because the upstream ones were intermittently sluggish making me run lean on pulls). None of these remedied the WOT 4.5k misfire.

In my case, the issue was one of the two things (or both): 1) when I replaced the valve covers on both sides, the pcv crossover pipe (bridging the two cyl heads front of the lower plenum) had a hairline crack in the plastic (probably introduced when removing/installing it). Replaced with a silicone one. 2) VVT solenoids - The screens and pin didn't look dirty or caked and when I applied 12v, the pin actuated. But after cleaning (alternating open/closed a few times) I realized it was a little gummed up because it made a happy/audible "CLICK" when opened.

I did both of these at the same time, but they both were issues that could have created the problem. Reset the ecu did all the relearns and haven't had a misfire or a stumbly idle since.