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Help - Misfire issues
Hey everyone, so I am new to this forum because I am looking for help with an issue I am having. I am trying to track down the problem, but keep coming up empty handed. So I recently went forced induction with my Z. It’s an 06 with 50k miles on it. It has always ran great and never had any issues. Right after getting it turbo’d a misfire has been occurring (P0300) , which seems like it could be anything. The car has a new fuel pump, new injectors, new spark plugs, new coil packs, great compression, and didn’t seem to be registering a misfire when It came off the dyno after the tune. It has a normal cold start but a really bad warm start. The next thing I am going to look at are the fuel dampers. Do you guys have any thoughts? Could the fuel dampers be causing the issue? I’ve watched the AFR at idle and it bounces between 14-15 every four seconds or so. I’ve checked around and can’t seem to find any vacuum leaks. Another thing that has me scratching my head, is I just noticed the little red security light now stays on when the engine is on. I don’t know if the problems are linked or it’s a separate issue. Another thought I had is the wire harness for the oil pump may be tapping into the fuel pump wire causing some sort of voltage drop? what are your thoughts? |
A large number of unknowns here. Since you modified your Z with a turbo, I assume you used a tuner shop to plan the build, installation, and handle the tuning? They would be the best ones to work with having the most knowledge of the build. This could be anything from a fuel map issue to the wrong types of spark plugs. There's a laundry list of things that could cause a misfire with an NA Z, add FI modifications into the mix and things only get worse. There might be some knowledgeable people on the forums here regarding turbo applications on 350Zs, but at the end of the day you're best bet is to have a professional tuner take a look.
-Icer |
I did take it to a shop for tuning but I installed the kit myself. It’s the STS rear mount kit. The kit was easy to install and the shop looked over all the work. They performed a compression test, boost leak test, and installed the new plugs and injectors. I would have loved to have had the shop fix the issue for me but they are claiming the misfire is not their issue. They said it’s a tuning issue. The tuner they have come in, only comes in once a month and is impossible to track down. The shop had already lost money on my car because they damaged something and had to replace it. They don’t want to have anything to do with it so I’m not sure it’s a tuning issue as much as they don’t want to deal with such a broad problem. My thoughts are an issue that Z’s are know to have that may have only been exasperated by adding forced induction, like causing a sensor to go bad or something. |
Clean the MAF sensor yet?
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STS rear mount kit and what are you tuning with??
Your problem is a result of the warm / hot starts. Especially if you have to crank the car more than a few seconds before it catches and turns over. The OEM ECU registers 'misses' (ie failed ignition attempts) based off the cam position and crank position sensors and if it senses more than a few attempts it'll kick the CEL. This is especially problematic on turbo'd cars because the air flow going into the engine is relatively restricted. It's probably worse with a rear-mounted kit. The fuel sprays on the hot manifold / hot valves, quickly evaporates and doesnt make it's way into the cylinder and thus the engine doesnt have a air:fuel ration that'll catch. A few things you can try ... If you can vent your engine bay to release heated air it'll help keep the manifold and plenum cooler which will help reduce the amount of fuel you lose to evaporation. you can add fuel to your initial fuel pulse crank table where you engine coolant temp is high/higher and add fuel in the post-start table those first few seconds at high engine coolant temps (prime pulse and post start enrichment in haltech-land). you can adjust your ignition timing in the coolant temp correction table so that in high vacuum/high temps take timing out (Obviously dont mess with your tune unless you know what you're doing ... which you probably dont, so mention these to your tuner and see what they think.) If you crank position and cam position sensors havent been replaced in a while consider replacing them. learn how to start your car when the engine is hot ... for me, it's a quick crank, wait a second and then try it again. If my engine is hot and the car doesnt start within a few attempts, I spray starter fluid into the plenum via the brake booster port and usually that does the trick. |
Yes, sorry forgot to mention I cleaned the MAF sensor. The other thing that I forgot to mention is on the car is a vented oil catch can. I will have to look into those fueling sortware issue possiblities. See if I can get ahold of the old tuner or just find a new one. The car is tuned by the UpRev software. The owner of STS recommended using it if I wasn’t trying to achieve any insane hp numbers. I will pull some of the sensors, inspect and clean them. Would adding the turbo cause a sensor to go bad? The CEL didn’t come one until the next day after tuning when I was taking short 10minute drives and letting the car sit for 10 or so minutes, and jumping back in. When i I warm start the car, I haven’t had to re-crank it. It’s just a slow start as if it’s almost not going to. The misfire is always happening though when It idles. Every couple seconds I can hear the exhaust caugh and see the afr go a little lean. When I’m driving and on the gas the afr seems to hold steady. I read a lot of other posts from people with misfire issues. One of the things that was a fix for someone else, seems like a plausible fix to me, are the fuel pampers going bad. Can the issues that I am having be caused by them going bad? The rest of the fuel system is pretty much upgraded so I wouldn’t suspect a new part being bad. ( that is unless it is a fuel tuning issue) |
You can pull them and clean them but I would do a little research on how to clean a hall sensor ( I don't know the best way and if any products are going to harm them). Likely the sensors are fine but it may be good practice to replace them (how many miles on the car??)
There may be some guys with more uprev knowledge than myself that can help. |
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