Car sputtering and P0302 all of the sudden -
05-20-2022, 02:41 PM
Hey All,
All of the sudden my car started sputtering sporadically under WOT and boost. Nothing changed in 15K miles... The sputtering eventually lead to the car acting like it lost a cylinder (or more). Massive lost of power and sounded like a Subaru. Also threw a CEL (P0302).
Mods are: secondary down pipes, Mid-pipe, axle-back, BMS 450whp kit w/ EWG and Fuel connector wires. Running 93 oct.
Usually I run Map2, but I've gone back to Map1 for safety reasons and did some logging. I've attached my logs for review, but it appears maybe the car is going lean all of the sudden... no idea why.
Thank in advance for any help you can provide.
Last edited by DouglasHammond; 05-20-2022 at 06:47 PM..
P0302 is misfire cylinder 2. Plug, coil, or fuel injector. You could move plug and coil to another cylinder to see if misfire follows to troubleshoot them.
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Thanks guys. That was going to be my next troubleshooting step, to check the plugs, particularly start with cylinder two. Figured I would check though in case there was something that looked off that I wasn’t seeing in the logs or if there was a common issue you might know about. The plugs only have about 10,000 miles on them in the car doesn’t have much more.
Definitely cylinder 2 spark plug. I don't see anything concerning on the plug itself other than than the tip burnt off (broke off maybe)… I don't see a bunch of pitting or anything weird to indicate knock. Thoughts?
Pulled the manifold last night and replaced all six plugs. Found another plug that had a massive gap on it. Took the car out this morning and gave it a good rip, feels so much better! The problem appears to be 100% resolved. I took a third gear pull log to share for a second set of eyes, but looks clean to me.
Two random questions, unrelated to the initial issue.
1) Are the factory valves cast and not forged? I looked through the intake manifold and they did not have a smooth surface from what I could see. I’ve attached a pic for reference.
2) Does my boost look right for map2, 17psi max, tapering to 13psi by redline.
Thanks!
Last edited by DouglasHammond; 05-24-2022 at 07:13 AM..
Hey there, when you were having issues was the car shaking pretty violently while you tried to go?..i feel like i have the same thing going...if i give it 50% throttle it starts sputtering. if i let off right away its fine..if i keep on it the car goes bad. i replaced all 6 plugs..one had missing electrode/huge gap. but the problem is still there for me. just trying to figure out if i still have a bad plug or a bigger problem, thanks!
Hey there, when you were having issues was the car shaking pretty violently while you tried to go?..i feel like i have the same thing going...if i give it 50% throttle it starts sputtering. if i let off right away its fine..if i keep on it the car goes bad. i replaced all 6 plugs..one had missing electrode/huge gap. but the problem is still there for me. just trying to figure out if i still have a bad plug or a bigger problem, thanks!
Hey Buddy. For me, the car ran fine 95% of the time. It was really only in high throttle/high boost situations that it was breaking up. The exhaust started sounding like it was sputtering / popping while shifting 2nd to 3rd, and then there was a lot of hesitation/mild shaking when breaking up. 2 of the 6 plugs for me ended up missing electrodes (or burnt down possibly). BIG GAPS! Both middle cylinders on driver and passenger sides.
I took the time to carefully re-gap to exactly .022 on every plug and things seem great now.
For what it's worth, you and I have very similar mods.... sucks to have to pull the intake manifold again though if you don't have to. Could be a good place to start though if you know you don't have a bad boost leak, no CELs, or something else going on though.
seems like a might be in a little worse spot than you...i mean i can go down the highway fine..100mph is fine as long as i dont try to get there quick. when its not in drive i can rev the hell out of it without issue..problem is when about 6lbs of boost comes on it goes wonky
im going to try and change the plugs yet again just to be sure i didnt mess it up or crack a plug. the only time i get a CEL is if when it starts sputtering i keep on it.
thankfully ive become pretty good getting #3 out without taking the top off lol. the coil is the worst part of that.
probably be the last thing i do before putting it back to stock and taking it the dealer and acting dumb lol...thanks again!
Car sputtering and P0302 all of the sudden -
05-20-2022, 02:41 PM
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