03 350z misfire help..

[rob666]

hey everyone , new to the forum and new to 350s. looking to get some help from the experts.

so recently i bought my first 350, 80 k on it and excellent condition from what i can tell.

https://scontent-lga3-1.xx.fbcdn.net/hp ... e=5686CD13

anyway i bought it saftied and etested and was pretty confident with the purchase with the pretty low km.
car seemed to run great and sounded good too..

2 days in of having it i started to notice a slightly rough idle but didn't think to much of it but then my aces light came on. since then its gone off them came back on twice. some times it idles fine some times it doesn't.

i contacted the seller he and thought the intake got wet or it needed a plug or something. so i ordered a cover for the intake and got the code checked . p0300 , so random misfire. i took it to a local shop and the used a camera scope to check it out and they said they could see all the cylinders misfiring randomly. they checked my spark plugs and some of them had oil on them . immediately he said to go any further he's going to have to risk breaking the wiring harness to find out for sure which is approx 800 to replace for parts and labour. he said without checking he thinks its a bent valve..ouch. but after doing some research i fund out it could be many other things like seals. Im no car expert but i feel like id be noticing a lot poorer performance from a bent guide? not to mention it has low km and has never been raced or on a track (apparently).

i looked up videos on replacing seals and it looks like a pretty big job compared to other engines iv seen.

does anyone have any similar experiences or and ideas of what it could be or if they agree with that mechanic? i know I'm probably going to have to get someone to start digging for the problem regardless. but the shop told me id be looking at approx 2300 bucks for parts and labour for bent guide.. i could almost get a new engine for that.. maybe he's just taking me for a ride? i don't know .. any input at all would be greatly appreciated

Rob.
(sorry for double posting think i had it in the wrong spot... new to forums)

[evildky]

This is trouble shooting and where a good tech proves his worth. I'm guessing from the vernacular you are somewhere in europe? So finding your location isn't likely to lead to any shop referrals. A bent valve while possible isn't likely but a leakdown test can help point to the issue being one of compression loss be it, ring, valve, or HG. If you mechanic would rather tear the engine apart than do a leakdown test, find a new mechanic. First thing I'd do is start moving as many components as possible between cylinders. Moving the plugs and cop's from any suspect cylinder to a known good cylinder is a quick and easy way of ruling out those components. Moving the fuel injector is a bit more work, beyond that it's a leakdown test.

[Brad_G]

I'm actually trouble shooting the same issue with my 03 as well. So far I've changed the spark plugs. I've got new cop boots and springs coming in tomorrow and I'll have those on by the afternoon. I'm just trying to factor out the ignition side right now. If those aren't the problem I'll start moving into fuel components and into the heavier stuff later. If i find out anything that works for me I'll definitely let you know. Lets hope for both of us that it's something "simple" and "easy" to fix.

[rob666]

This is trouble shooting and where a good tech proves his worth. I'm guessing from the vernacular you are somewhere in europe? So finding your location isn't likely to lead to any shop referrals. A bent valve while possible isn't likely but a leakdown test can help point to the issue being one of compression loss be it, ring, valve, or HG. If you mechanic would rather tear the engine apart than do a leakdown test, find a new mechanic. First thing I'd do is start moving as many components as possible between cylinders. Moving the plugs and cop's from any suspect cylinder to a known good cylinder is a quick and easy way of ruling out those components. Moving the fuel injector is a bit more work, beyond that it's a leakdown test.

thanks for the reply guys... I'm actually in canada , ON. Ill definitely be looking into that leak down test, id rather find the issue then just keep replacing things until i find it. but id definitely appreciate it if you kept me updated on yours swell BG. i hope so aswell

[Brad_G]

I'll definitely keep you updated. Honestly if this doesnt fix the problem then im just gonna pay the $90 to have a shop run diagnostics on it to find the problem. I'm tired of messing with it lol

[rob666]

i made the mistake of taking it too a local shop that charged me 180 just too say they think its a valve but can't look without taking off the wiring harness . but i hear yea

[Brad_G]

So i just got done changing the boot an spring for all the coil packs. No misfire at the moment and the code cleared itself. As it stands it looks like that solved the problem. One thing i did notice is that the old spring are about 10mm shorter then the new ones. Maybe there just wasn't good contact? I'm not sure exactly but it looks like that solved it for me. Maybe look into swapping those out on yours. it's pretty cheap for all six of them and swapping them out isn't to bad of a job. I hope this helps you out Rob. I'll let you know in a day or two if this solution was definitive for me since it was an intermittent misfire and didnt always do it.

[rob666]

thanks a lot man good to hear. lets hope my issues the same lol

did you have oil on your plugs aswell?

[Brad_G]

I didn't see any oil on the plugs. Unfortunately as of this morning it looks like that wasn't the solution. So..... back to the drawing board i suppose.

[rob666]

update:

just got my car back from a new shop.. guy says its 100 percent cam/crank sensors... any thoughts? after searching iv found that these seem to go often

[Brad_G]

Rob I was just doing a little research to feed curiosity and i came across a recall that may have been the answer to our problems. Take a look at this, It may be the reason the shop told you it was the crank or cam sensors. I'm gonna try to find some time to have mine checked out. I suggest you do the same and if it was the problem then Nissan may reimburse you at least some of that money you spent at the shop if you had them do the work.

Announced
NOVEMBER 17 2003
NHTSA Reference
#03V455000
Number Affected
630,000

Summary: On certain passenger vehicles, the circuit board for the crank position sensor or cam position sensor may have an improper solder joint due to solder deformation caused by heat stress accelerated by the existence of flux residue during the soldering process.

Consequence: This could cause the "service engine soon" warning light to come on, create a no start condition, cause reduced engine power, or cause the engine to stop running without warning during vehicle operation, which could result in a crash.

Fix: Dealers will replace the crank position sensors. Camshaft position sensor(s), and in some cases, the variable timing control sensor(s). Vehicles involved in a previous recall campaign, 01V357, are also included in this new campaign. The replacement sensors used in that campaign are also affected. Owner notification began on December 22, 2003. Owners should contact Nissan at 1-800-647-7261 or infiniti at 1-800-662-6200.