Hello everyone. I'm new to this site and I'm hoping you guys have some info related to my issue. I recently purchased a 2010 SHO in april with 44K on it. The car is in bone stock form. The issue that i have is after the car is driven for about 20min, then i go to WOT, the car has a horrible misfire. The check engine light will start flashing and everything. Once that happens, if I drive the car normally for 30-60 seconds, i will clear right up and the light will go out. If I go to WOT again, the process will start all over. Ive pulled codes P0300-P0306. I've replaced all 6 spark plugs with the iridium ones that Ford offers for it and had the latest reflash done with no change what so ever. Whenever the motor is cold, it will never misfire and runs great. The problem happens about 20 mins after you drive it. It doesnt matter if its city or highway. I can get the car to do this on a daily basis. When driving normally, the car runs great until you go to WOT. Any info or advice related to this issue would be great. Thankyou!
SHO misfire
- Thread starter bully60
- Start date
I moved your post to the new troubleshooting board:
http://www.ecoboostperformanceforum.com/index.php/board,141.0.html
Also removed the other one in the build thread board.
Thanks for joining BTW!
http://www.ecoboostperformanceforum.com/index.php/board,141.0.html
Also removed the other one in the build thread board.
Thanks for joining BTW!
crash712us
New member
Possible dirty or bad inhector or sludged valves.
Welcome to bully60 & his 2010 SHO 
Back the vote for an injector related problem, possibly fuel pump under load. Rarely will it be wires/coils/PCM. Also since you are gen 4.1, I would check for chafing knock sensor wires. There is a HOW TO on here to do just that.
http://www.ecoboostperformanceforum.com/index.php?topic=554
Back the vote for an injector related problem, possibly fuel pump under load. Rarely will it be wires/coils/PCM. Also since you are gen 4.1, I would check for chafing knock sensor wires. There is a HOW TO on here to do just that.http://www.ecoboostperformanceforum.com/index.php?topic=554
My thoughts are:
Sensor failure... Especially if it only append after warmed up and not in open loop before O2 sensors warm up.
Failing coil... Problem under load or chaffed knock sensor wire as Manu suggests.
An electrical connection in the ignition... Problem under load... Try putting dielectric grease in connections outside computer and check for corrosion.
Bad/dirty injector.
Do you data log or can you read OBD2 codes? Is it always the same cylinder?
There have been numerous reports of stretched timing chains on rear bank... This one usually sounds like it is knocking at startup.
Sensor failure... Especially if it only append after warmed up and not in open loop before O2 sensors warm up.
Failing coil... Problem under load or chaffed knock sensor wire as Manu suggests.
An electrical connection in the ignition... Problem under load... Try putting dielectric grease in connections outside computer and check for corrosion.
Bad/dirty injector.
Do you data log or can you read OBD2 codes? Is it always the same cylinder?
There have been numerous reports of stretched timing chains on rear bank... This one usually sounds like it is knocking at startup.
UPDATE: I did check my knock sensor wiring and it is in fact chaffed. I wrapped some foam tape around it. Coming home from work today, I went to WOT and it was much better. It had some hesitation to it but nothing like its been doing. No check engine light came on either. As far as the fuel injectors, wouldn't the misfire be at all engine operating conditions instead of just WOT? And like I said, the car runs great when the engine is cold. To my knowledge, engines require more fuel when cold. I've never once had any issues on a cold engine. I do get a knocking sound on startup whether the engine is hot or cold. The noise is gone in 1-2 sec. As per the Ford dealership, this is a normal noise. Once again, any advice would be great. You guys seem to know more than anybody else.
If the fuel injectors are not operating optimally, you could see them "fail" when maximum load is demanded, i.e., WOT. I don't know if the injectors are balanced as a set when issued with the car from the factory, but you can bet that after use, they won't have equal threshholds where an event is triggered. Simplest thing to try first is to run some Techron or BG or similar quality FI cleaner through the gas tank, see if that helps the hesitation issue. Keep an eye on the spark plugs to see if the engine is running lean/rich. Don't want any plug wet with fuel for sure!
Valves could also be carboned, as Crash pointed out earlier. Common problem with GDI engines. There are solutions from various aftermarket providers to clean up the carbon, or you could have the valves blasted with walnut shell media. If you (or a trusted mechanic) have access to a boroscope, you can check to see if this problem exists in your SHO.
The 1-2 second knock could be insufficient oil pressure at engine start. Sometimes it can be resolved by changing oil filter brands. Most have had good luck with the Motorcraft "OEM" filter, some have had to use another brand to stop the noise. In an extreme/more advanced case, as BiGMaC pointed out, you could have a loose timing chain issue.
Valves could also be carboned, as Crash pointed out earlier. Common problem with GDI engines. There are solutions from various aftermarket providers to clean up the carbon, or you could have the valves blasted with walnut shell media. If you (or a trusted mechanic) have access to a boroscope, you can check to see if this problem exists in your SHO.
The 1-2 second knock could be insufficient oil pressure at engine start. Sometimes it can be resolved by changing oil filter brands. Most have had good luck with the Motorcraft "OEM" filter, some have had to use another brand to stop the noise. In an extreme/more advanced case, as BiGMaC pointed out, you could have a loose timing chain issue.
