Help! Cant figure out Misfire

[Smoky10]

My car just recently started throwing the stabiltrack and random and multiple misfire code.

P0300
P0302

I have changed the plugs and the wires. Even switched the coil pack. My mods are in my sig can anyone point me in the right direction? It doesn't throw the code and I don't feel the skip until around 45-5500 RPMs

Brandon

[Birm]

Who did your tune? Have you confirmed your afr is not too lean? This can cause a misfire. If it is not in your tune then could also be the injectors clogged, A weak fuel pump can also cause you to lean out..

Have you checked your gaps? If you eliminate those two then you may have to check your exhaust valves or head gaskets....

All of which can cause a misfire and throw P0300 P0302

[Rhino79]

Check the valve springs. Sounds like it could have one of the outer springs broke.

[Smoky10]

What does that sound like?

[Rhino79]

It may not make a sound other than just misfire, should be easy to rule out. If you have a broken spring you'll be able to visually see it with the valve cover off

[Smoky10]

I'll pull the cover and check thanks

[Tampa Tuning]

There are many factors that will cause the engine to run rough and generate a diagnostic trouble code of P0300. It should be determined if its an old code first, or your CEL returns flashing

Sometimes your vehicle will run just fine but the computer can still store a P0300 code in the computer. A misfire will always fall into one of three categories. Spark, fuel or mechanical. Bad tune up parts or incorrect ignition timing will cause a misfire under the spark category.

Low fuel pressure, leaky or plugged injector or even a vacuum leak will fall under the fuel category. It could be a lack of fuel or it could be too much fuel. Tight valves, broken valve springs, worn valves, compression rings or even incorrect valve timing falls under the mechanical category. All of these issues can cause a P0300 code in the computer.

If you are having a misfire, your calibration expert should have a PID set up to tell you which cylinder to narrow down your search for a fix.

Phil
www.TampaTuning.com

[mercedestech]

He is also setting P0302, not just the general P0300. I would definetely start with cylinder number 2, and like rhino79 stated a missfire only at higher rpms points to valve float. Definetely sounds like a weak or broken spring.

If it misses anytime you are under load, then usually it is ignition related.

Any injector problems, or mechanical problems concerning valve timing etc will be present all the time, not just at the upper rpm ranges you mentioned. A fuel pressure issue, or maf sensor issue will set faults on all cyl's (P030* where * is the cyl number) not just one like you have. P0300 will almost always acompany an individual missfire fault and doesn't mean all of the cylinders are misfiring.

Take rhino's advice and look closely at cylinder number two's valvesprings.

[mercedestech]

OP any update?

[Smoky10]

Not yet. Had to make sir my truck was good before I could tear into my car.

[SC2150]

Pushrod length correct for proper preload? That can as well...

[Smoky10]

Yeah it was. Unless the push rods are bent. I've been running this setup for over a year and this problem just started

[boat rx]

Just curious, if you don't mind saying what type of valve springs were you running?What are the specs if you know that?iI had a similar problem with the same cam.it turned out to be several broken springs,broken valve guides,and most of the rockers were junk.Turned out the biggest cam manufacturer won't admit that the springs they recommended for stock valve train have to much open pressure to run with Lsk lobe and .641 lift.Contact Brian Tooley for some good advice if this turns out to be you problem.Been there and done that.

[Rhino79]

Lsk is a very very aggressive lobe and it will require routine spring replacement no matter the brand. That's a pure race lobe and while power is superb with it, it's very taxing on the valve train.