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Discussion Starter #1
So i bought my wife a newer car to get rid of her terrible mustang and now its backfiring on me. I bought the car about 5 months ago and it has only ran for 3 of those months. It is an 03 sentra ser spec v. Things ive replaced so far are all gaskets on the top end (including headgasket) both oxygen sensors, thermostat's, brakes all the way around, spark plugs, timing chain tensioner, and many other things not engine related. I followed the instructions on this site that i found to do the headgasket. I got the ajusa headgasket set and arp head studs. After i replaced it i put it all back together and it ran good, and kinda had a rough idle but it always had a rough idle since we got it. After two days of driving it with no isues she went out to drive it to work and she has a very hard time starting and it idles terribly, it doesnt seem to have an issue revving but it pops alot. It shows p0300 random cylinder missfire as the only code although i did notice that its reading ignition advance pegged around 27-28 degrees at idle, wich is way too high. I have checked and the previous owner replaced the cam and crank position sensors over to the metal ones. I have not fucking clue how this could happen, i own a 07 civic si and a 91 240sx and neither one has given me as many issues as this car since day one. Im pretty shure its not something mechanical since it didnt happen immediatly after i started it after doing the headgasket, and the car ran and drove fine for two days with no codes after that. Ive tried looking all over the place and the only two things i seem to be pointed towards are bad coils or a bad ecu. If anyone knows something to look for or check or has had issues like this please help me.
 

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Did you replace all that stuff to attempt to get rid of the bad running conditions??

These cars are also widely known for bad MAF sensors too.

But also you may have possibly jumped time in the chain. If the came is that far out with a random miss, a timing issue or cam phaser is suspected. At work its actually happened to us 3 times in the passed 3 months, and twice in the last few weeks. Even with new parts.
 

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Discussion Starter #3
The car has had a weird idle since we bought it but never like this. I replaced the o2 sensors because it threw a code for bad o2's, and it had a code for random cylinder miss before the head gasket. I replaced the headgasket because it was blown on cylinder 3 and 4 and was blowing white smoke on start up. idk about the timing jumping, but idk why it would jump since it has a new tensioner and it ran without any issues for two whole days with no codes.
 

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did you prime the tensioner a few times after you installed it? and made sure that the engine was at TDC? not trying to belittle you but there are some thing we should know before trying to troubleshoot. also, do a compression check, make sure numbers are within limits. its not probable that its your coil packs but with the car running you can unplug each coil pack and see if there is an audible change. also your car will sound cammed. if you remove the connect on the coil pack and nothing changes you more than likely have bad coil. also, did you do the idle relearns?
 

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I am in the same boat as you, having just purchased an 02 with a blown head gasket. While I only did a factory headgasket replacement (stock gasket/studs), and no extra's, I also had a major issue with idle. My problem ended up being a pin fit issue on my maf sensor connector. It was causing the ECM to receive an extremely rich reading from the MAF, because the ground side of the circuit had an excessive voltage drop. My car would almost never idle, anytime I was coasting off throttle it would die. I would get p0300's and p0172 (fuel system rich, may have been 171 I never remember). I've also had pin fit problems on my throttle actuator. 14,000 miles and 5 months later and I haven't had an issue since.

These engine harnesses aren't the greatest and can cause some pretty strange issues that make the car seem possessed. I've seen lots of people shot-gunning parts to fix these weird issues when they just needed some extra time and attention. My own car being a perfect example. I probably got it for so cheap from the PO because the throttle chamber had been replaced 3 times, and the ECM twice for the throttle issue which turned out to be a poor connection.
 

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Discussion Starter #6
I have not checked any connections yet as i haven't had the time yet. I believe the issues to be electrical only because this issue literally arose over night. If it has in fact jumped time i will be able to see that on a compression test since it will have low compression. Im hoping it hasnt jumpd time but if it has it shouldnt be that difficult to fix or at least i hope not. i have read that many people have had issues with coils even though they are sparking. and i have read that many people have ended having to swap ecus out just to fix issues like this because the ecu has malfunctioned. I will be driving it to my job today since i work at a hyundai/nissan dealership and hopefully my buddy can figure out wtf is going on exctly with it. If it is electrical such as a bad maf, bad crank/cam sensor, or bad coil where can i find the acceptable ohm tolerences for each one since i dont have the fsm.
 

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Discussion Starter #8
well looks like i have it figured out and ive been drivng it around since lunch. My problem seems to be that the mechanical advance on the intake cam got stuck in the fully advanced position. This was causing the computer to flip out and throw more ignition timing to try and fix the 27 degrees it had at idle. I took it to my coworker at nissan and by the time i had driven it there it had retarded itself back to normal. I had him look at it and he couldnt do an idle relearn on it for some reason so he just manually went in and changed it to 850. apparently the computer was set at like 600, wich was way too low. He did tell me that he has personally seen this happen before when doing headgasket or cam work like this. He had the same thing happen to him on a 350z that he rebuilt. He believes what causes it is a lack of oil in the mechanical advance mechanism after it has been taken out of the car and sat for a few days. Hopefully this doesnt happen again but if it does i will be changing out the advance mechanism and ocv plate with new ones. I hope this helps out anyone else with similar issues cause it pissed me off for a week trying to fix it.
 
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