Hey all. I have been fighting some performance issues with my LNF for a few months now, and have slowly been picking at it and making a bit of progress. I managed to bring the misfire from Cyl 1, 3 and 4 at high throttle input to a cylinder 1 Miss under some WOT conditions, usually not if i roll onto the throttle but if i put my foot into it fast it will missfire. Sometimes. When missfires throws a P0301 Cyl 1 misfire code.

I have also noticed an occasional 2kprm hesitation or shudder. Most common in 5th gear going up slight inclines when it builds a bit of boost. No CEL/MIL lit when this happens.

Also has the occasional cold start problem throwing a P0014 Cam Position code. I believe this to be unrelated as its only on cold starts however someone might have more input on this. Have replaced the actuator on the valve cover to no change.

 

Plugs changed recently?

 

Does ur exhaust sound like a machine gun when it misfires?

 

Plugs were changed and gaped to 0.035 about 3 months ago when I first got the car.

No machine gun sound, I dont believe its an injector seal issue, it just sounds like a dead miss to me sometimes the wastegate will release pressure if I stay on it but i usually dont let it miss more than a couple times before i let off.

It could be an injector seal issue, But id like to eliminate everything else first since theres no real way to test that and the tool is expensive.

 

Compression testttt! But besides that, boosting at a low rpm is a no no

We should actually ask what mods and tune, plus how many miles.

 

And when I say builds a bit of boost at 2krpm I just mean enough to bring the gauge to 0-5kpa, not actually bringing it into full boost just enough to get it up the hill.


Sorry. I meant to put some of that info in this thread. It's all in my old one but to sumarize

3bar map sensors and 20psi tune I believe stock gms1
Catless dp
K&n
Injen upper cp

Compression test 155 +/-2 cyl 1,3,4 129 cyl 2. Cylinder 2 is within spec but it is low, remember the misfire is cyl 1 not 2. Once the weather warms up I'm going to re-test dry and wet to see if it's worn rings or Coked valves but I don't think that's causing the problem on the different cylinder.

Plugs are ngk iridium, I know I should have acdelco but I already bought these since the gm dealer was closed the day I did it. Gapped to 0.035.

100k km which is roughly 60k miles I believe.

The car pulls really hard when I roll on the throttle and when it decides it does want to go wot without misfiring. The intermittentNess about this problem makes me have a hard time diagnosing it. 80% of the time it misfires, the other 20 it runs like a dream. Doesn't seem to be weather/temperature/moisture dependant.

I have changed both o2 sensors, cylinder 1 coil with acdelco part, cleaned the upper map sensor and the maf sensor, checked purge solenoid, tightened my charge pipes and replaced with tbolt clamps, ran intake(post turbo) and fuel system cleaners.

 

oem plugs gap to .032"
it matters

 

Ive read in the past that people had issues with NGK Iridiums even though technically they should work.

 

in for plugs

 

I guess I'll dump $17/plug on Delco.

I'm still not overly convinced it's a plug issue but as soon as it stops snowing I'll gap down to 0.032 and see if there is a change.

 

Advanced Auto usually has ac delco plugs for less than that

 

You mean $6 per plug of course.
Amazon.com: ACDelco 41-108 Professional Iridium Spark Plug (Pack of 1): Automotive

 

Yeah I bought my plugs on Amazon. Thats the price I remember. They come pre-gapped.

 

OEM Plugs at .032. Done

I had this same problem when I first bought my LNF and the PO had put in NGK Iridiums gapped at .0036 and I had a weird misfire.

 

If only they werent double the price in Canada hahahaha.

 

Yup Canada is gay that way.

 

Right now it sucks being in canada.

On top of everything its been cold as ****.

I have a video to post later today, I think today gave me my first sign of blown injector seals. Got more of a machine gun popping today rather than the usual misfire.

Does anyone have any info as to why the injector seals cause the misfire? Is it a loss of compression? leaking boost? Something to help me better understand the problem at hand before i spend hundreds of dollars getting my injector seals re-done at the stealership.

 

Its short but hopefully you can hear it ok.

Thats the worst its been since before i fixed my boost leak. It was also -15 and snowy, but I dont think that makes much of a difference.

 

Is your car up to temp when it happens?

I know leaving work and having to pull onto a busy highway I can get a misfire if the car's cool.

 

Down shift before you accelerate like that sounds like you're bogging the engine down then it misfires. It's hard to tell from the video what rpm and what speed you were going, but you should be above 2500rpms minimum for a partial acceleration (20-40% throttle) and above 3000 for more throttle.

Have you pulled the plugs to see what the electrode is telling you? (the color of the electrode or excess oil/fuel on the cylinder giving the misfire compared to the other cylinders)

 

Yeah the car was to temp when I did this. I usually wont be very hard on it when its cold.


I never really thought of this. I was going fairly slow in 3rd i believe( maybe 2-2500k rpm). It does misfire when I hit the throttle at higher RPMs but not as bad as it did in the video.

I will try to get a video of the misfire while driving in better conditions today if I can find some dryer roads.

As of recently I have not pulled the cylinder 1 spark plug, but as of a couple months ago it did not seem different than the rest. I will check again.

 

I used to have that issue when it rained sometimes. It was very audible. I actually have no idea what fixed it.

I have done new plugs, dielectric grease on the stem of the spark plug. That's about it.

 

The issue doesnt seem to be weather related, but I'm working on getting some spark plugs, I'll put some di-electric on it when I do and see what happens.

 

I read back through this. Still could be coked valves for sure. But I really only got those during Cat warm up. But I cleaned mine at 70k miles.

 

loaded up the engine, ran it a 3k then went on the throttle, same result.

New codes P0099, P2199.

I think my MAP sensor needs another cleaning.