I dont know how to explain this. But to spare everyone the story...my car started idling real low and lumpy and stalling out this morning. I have no iacv on my 3.5 swap and it has a little hesitation on cold start ups which i've believed to be something with my TPS or PF tb.
But anyway, so i got out to see what was wrong with the car and there was NO oil cap on the valve cover. I know i checked the oil last night and topped it off and thought I put the cap back on, but somehow it wasnt on and i have no idea if maybe i loosely put it on and it just came off while i was driving today. But i've driven a good 60 to 70 miles since i checked it last night. Im not sure how the pressure in the valve covers works. I dont think much oil splashed out, although some did. I got NO OIL PRESSURE LIGHT...and the oil pressure sending unit is not old at all. Theres still plenty of oil in there when I checked with the dipstick.
When i was driving it wasnt allowing me to rev past 2500 and i thought it was some kind of limp-mode...but i dont think thats really the case.
I managed to get home and the extra 3.0 oil cap i have fit on there but i'm not sure that its creating a seal...because the car is still idling like **** and stalling out and sometimes not even revving up. It revs up very lumpy as if it has a bad MAF or some kind of intake leak.
Im buying a new oil cap right now online but what else could it be if this is not the problem? What damage could I have done by driving with no cap on there.

 

cant go past 2500 rpm is usually a maf issue

no iacv ? that cant be good

any codes ?

 

i checked the codes and its just the usual auto tranny, iacv ,02 sensor codes I always get because of the 5 speed and 3.5 swap.

i could rev past 2500 if i wanted to, it just started getting very very choppy. The thing is, I unplugged the MAF to check if it would go into the preset fuel maps mod or whatever it does, and it kept stumbling all over the place...so i knew it couldnt be the maf.

unless the 3.0 cap is still leaking...i cant imagine whats causing this ****..

 

Sorry man im not really familiar with the 3.5 swap and all that, and thats a lot of codes btw. even if all that stuff is not broken (o2's and so on) the ecu thinks it is, so that could be part of the problem.

Did you do the swap yourself or let a shop do it ? if a shop did it then go back there and ask to diagnose the problem if its possible.

Otherwise wait for members who are knowledgeable with a 3.5 swap to help you trouble shoot the problem.

 

Any supporting mods, EU/VAFC/etc?

 

i did the swap myself and its been running fine for a couple months.

i have no supporting mods. i was supposed to have my safc i bought a couple weeks ago but anyway.

 

nobody has any idea? i cant find a specified 3.5 oil cap anywhere...rockautos part numbers are the same for the 3.0 and the 3.5. gonna check the dealership

 

put the oil cap on

 

 

vq oil caps are interchangeable. most nissans are with a couple exceptions. want a billet nismo?

 

well the 3.0 one fits thread wise, but i dont think its creating a seal. Im going to pick up one from the dealership today and if that doesnt fix my problem I am seriously seriously worried about if maybe my timing chain skipped a link due to the pressure involved with the chain tensioners.
i always expect the worst, and i PRAY that this is not the case, but if it is...

 

and how much for the nismo cap?

 

the cap didnt solve the problem and im seriously stumped. it acts like a vacuum leak but i didnt find any lose hoses. I dont think its a timing chain tensioner problem really because the car seems like its fairly normal when revving but it cant hold an idle.
somebody please help.

 

I had similar issues with a bad cam position sensor. Check that out, cause depending onhow you mounted it or what oil pan you used, that might be the cause. Although I don't know what the low oil levels might have done to cause it--they seem un related. Anyway, check CPS (on the belt side, not tranny).

 

the problem with no oil cap is loss of vacuum. The PCV and front VC hose are both connected to the intake ducting, thus creating all sorts of problems. The maf wont read all the extra air. It doesnt need to be the maf thats broken.

 

^ true, didnt think of that, thanks

 

i got the new cap on tehre and it didnt solve the problem. I dont think the problem is as bad but its still there. Im going to check the CPS and possibly get a cheap replacement maf off the org here just to play it safe. I cleaned the maf with some of that spray but i dont know how much of a difference it made. the car still will idle really low and stumble around. I might try a new TPS too since i never could get that in spec on the PF TB.
thanks for your help guys, please dont leave me just yet haha i just gotta got a hot date tonight and shes gotta ride in my el camino.
i'll be back later on.

 

I could have told you that, unfortunatly I found this to late The pcv allows excess pressure to be vented into the intake manifold but it does not allow the negative vacuum in the intake tract to constantly pull in air from the crankcase etc. Anyways, unrelated to the swap obviously, what you need to do is check 3 things. The first you have probably already done, and shouldn't matter since you don't have any relevant codes, but still check for anything that could have been contaminated by oil splashing onto it. Next, hook up a vacuum gauge and check vacuum reading, if it is excessively low (16" or less) check for a malfunctioning/stuck/clogged/dirty (you get the hint) pcv valve by clamping some visegrips on the hose at the back of the IM temporarily, or attempt to 'suck' on that hose, also check for vacuum leaks elsewhere. Next in line would be a compression test, things like a holed piston can cause so much crankcase pressure that the cap could have blown off, I mean yeah it's a VQ but who knows........ but my vote is still on a bad pcv

 

thank you thank you thank you, i was wondering where you were.
The thing is, i replaced the pcv valve probably a month or two ago..so if it went bad i'd be surprised. but i'll check it anyhow. What should i be checking for as far as vacuum now? whats an acceptable reading?
i hate to say "i have a feeling" because i'm usually always wrong..but i think the maf could still be a possibility. I only say this because i got a MAF code which was most likely due to me unplugging it...but when i do unplug it, the car will not idle at all, it pretty much dies immediately instead of going into safe mode. im not sure if this is due to me not having an IACV or not i dont remember it doing that before when ive tested it though.
i'll be out in the shop tomorrow checking and testing as much as i can.