I give up, I need some help

[Bigred*]

K I need some expert advice.. So did a full engine rebuild (wiseco pistons, eagle rods) so a full rebuild. Got it done a couple days ago and all installed and it fired right up! Ran it for a while, finally got my valves to be quiet, was worried! Drive about 5 miles then took it home to change the oil and filter. Drove it to work the next day, for my convienece I left the hood off so I could keep an eye on everything, well while I was at work it rained which I didn't think would be that big of a deal but it was. Was leaving work, car started right up and as soon as i hit the street it took a dump! It was sputtering like it was misfiring, didnt matter what gear I was in i couldnt get above 20mph and the engine was trying so hard to even do that, so I limped it home with many stops on the way so as to not push it to hard as at this point it only had like 15 miles on the rebuild..

Got home and started going through all the possible problems.. I originally thought water had gotten in an electrical connector somewhere and still suspect that as all my plastic connectors are destroyed! The ones I could find online (coil pack and fuel injector connectors) those will be here Monday and be on the same day but I don't think it's those as I've checked them so many times and zip tied them on

I thought maybe it rained straight on my air filter and i sucked that water into my maf, so I have a new maf on my engine right now.. Thought I had finally found it! On my ptu I found three wires that were rubbed bare and were touching, cleaned them up, taped them up cleaned all the connectors anddddd did nothing!

Fuel pressure is reading 38 psi at idle which I've read is near perfect.. My timing light is having trouble picking up the signal off the coil pack wires so I have a buddy coming over with another one in an hour.
Ecu is giving me a 55 and no cel

Here's how it drives right now, cold start, it starts up the second it turns over, hot start it take a second at starts up real low rpms and then builds them up. idle has been rough and will idle at different rpms, sometimes then engine will run great at low rpms, and as soon as i approach 3000rpm it's like the timing gets way retarded and it won't go above 3000 rpms(limp mode?) most of the time though it barely runs and cant accelerate, i should also say there is a definite sound difference in the exhaust note cuz it isn't firing right.. Im baffled as it ran great before it rained

There are a few differences I made from when I pulled the engine, egr delete, ais delete.. Also deleted that thing on the right side of the engine bay that helps with warm starts to assist from vapor lock.. Cant remember it's abriviation.. Im at a loss and i really just want to be able to break my engine in right and have it driving good.. From what I can tell I have no vacuum leaks.. Also when I finished with my ptu I started my engine and forgot to put on my intake pipe from my ic to throttle body, the strange part is it started up and idled exactly how it has been, but with an intake pipe I feel like a normal engine should have run like crap.. Which I guess mine kind of is..

[Bigred*]

I should also say under no load the engine free revs just fine like there's nothing wrong.. Also reset the ecu (unplugged the battery for a couple min) with no prevail

[Bigred*]

One other update, when revved above idle, whether driving or not when I left off the throttle the engine just about dies, it drops down to about 100 rpm, somehow doesn't stall then recovers it self and the idle rises back up to normal.. I thought at first this was because the goofball who owned this before me threw away the diverter valves in place for some bov's.. However I just bypassed those bov's and capped the lines on the balance tube, and guess what, no change, just like anything else I try to fix..

[nissanfreak12]

A bad MAF will cause issues after 2500 rpms, some have had will not rev, misfires, just runs like crap. Something to look into.

Other things to check

CAS
CTS
PTU(kind of doubt this one)

The one thing to check first is boost leaks, this will also cause all the issues you are describing. Just pull out the good old trusty ohm reader and start checking sensors.

[DCaff300ZX]

I agree with Nissanfreak that your issue probably is in one of the areas he laid out, with a connector or wiring. Also of concern is your last comment on the intake piping, and a boost leak. It all leads to engine controls not functioning properly, I'd start testing these areas using the OSM tests so you have a baseline for things as your progress, trying to nail down the loose end wherever it is.

[Bigred*]

So here are my findings
Maf specs:
with key on engine off .8v from b terminal to ground, .8-1.5v with engine running
My maf is reading:
.41v with key on engine off and 1.45v with engine running

Cts specs:
2.1-2.9k ohms @69 degrees
.68-1.0k ohms @122 degrees
.30-.33k ohms @176 degrees
My cts:
At about 80-85 degrees however hot it is out here im sitting at 1.7k ohms

Coil pack wires are all reading 11.9 volts off the ptu key on engine off

Fuel injectors are reading 13.9 ohms on the lowest one, most right around 16 ohms and the highest at 19.3 ohms, but still in the range of 10-20 ohms as needed

[Bigred*]

Ok I found the problem.. Well main problem of a number of problems is its running way to rich! Pulled the plugs which mind you have like 15-20 miles on them and they were black as midnight! And that was my entire problem, they were so suited over they weren't sparking right.. So my local Napa had some NgK iridium IX plugs in Stock for $7 a pop, changed all my plugs, gapped to .040 (and no I didn't gap them by pushing on the center, gapped them from the side so all the tips are perfect, they were .030 out of the box) and running wise that seemed to have made a world of difference.. Im still puffing black smoke when I free Rev it and after a few miles of driving today it's getting back to where it doesn't want to run again.. Also I'm averaging something like 3-5 mpg!! I've gone through more then a quarter gas tank in under 30 miles.. Gotta figure out why it's fueling it so heavy.. Im thinking now my problem lies with my Cas or O2 sensor(s) which luckily I have 2 new ones right here, but if i could return them that's alot like $150 I wouldn't have to spend

[budget300zx]

first of all (if it were my car), Id go to autozone and rent a timing light. they are free if you return it in a reasonable time frame. If that doesnt help, Remove and clean the deposits from o2 sensors (will likely look like your plugs).

also is it tuned? ecu set for injector size?

[Bigred*]

So I got a timing light from a friend that worked out pretty good, engine was running at 10° btdc, i set it to 15° but didn't notice anything different.. Anyways all my plugs came in the mail today.. I was very surprised how green and corroded most of my injector plugs were,and i think it helped. I only idled in my garage for a min but the engine did seem smoother, but being that's it's almost 5am! I need to get to bed, take it for a drive tomorrow and see how it does, idle is considerably worse, but all the plugs on my iacv are shot.. Well All of my pugs were shot, replaced most tonight but I can't find where to buy the ones associated with the iacv.. And i think i crossed the wires on my air regulator, could that have killed it? I'll try unplugging it tomorrow and see if my fast idle valve takes over, cuz right now it won't idle to save it's life, chug chug chug stall.. But when I Rev it, it revs out pretty smooth.

Right now I'm running stock ecu/tune on stock injectors at 9 psi.. Built the engine so that when the funds are back i can do turbos+injectors+tune and itll all be good but that's at least another year down the road

[nissanfreak12]

Fuel injectors are reading 13.9 ohms on the lowest one, most right around 16 ohms and the highest at 19.3 ohms, but still in the range of 10-20 ohms as needed

Injector range should be between 10-14 ohms, anything out of that is bad. Your 13.9 one, is good, but will fail soon. The only way to fix is to replace. get the new styles, they should be oval, not square at the plug.

You stated in another post about green corrosion, go through all the plugs and clean that crap out. That will cause havoc on it running correctly.

10btdc is not horrible, ideal is 13-15.

[Bigred*]

Well the green corrosion was all over the injectors mostly, I should have tested the resistance again after I cleaned them all, but i definatly think getting the new plugs on the injectors helped a ton as I was able to drive it to work today it did sputter out and lose all power once I pulled over off the side of the road, but as soon as i pulled over it regained it's power so I could continue my commute.. I filled it up with fresh 91 octane and Lucas injector cleaner, cuz the 91 that's in it now has been there for a couple months, but it was near empty, gonna go drive it more when I get off and see if that helps too.. Low end power seems to be good, but first gear it sputters out at 4000rpm like it's hitting a Rev limiter, and it does that around 3000 rpm for the rest of the gears.. Also gonna go rent a nice timing gun from autozone just to double check cuz im not sure how reliable my buddies harbor freight timing light is.. Things seem to be improving! I'll be selling a motorcycle this weekend hopefully and i may just buy some 555cc injectors, or 750cc injectors with the money

Also I'm still running rich, when it starts sputtering at higher rpm, if I'm really on the gas I can see black puffs I'm my rear view mirror..

If the injector resistance is higher, wouldn't that mean I'd be getting less fuel? Higher resistance would translate to a weaker electromagnet, which would cause the injectors to not open enough or for long enough? Or am I thinking about this all wrong?

[budget300zx]

whats the boost doing when its cutting out?

my suspect list from here would be
1 boost leak
2 o2 sensors
3 tps out of adjustment
4 knock sensor
5 MAF
6 ground issue
7 compression drooped

[nissanfreak12]

If the injector resistance is higher, wouldn't that mean I'd be getting less fuel? Higher resistance would translate to a weaker electromagnet, which would cause the injectors to not open enough or for long enough? Or am I thinking about this all wrong?

Logical thinking, yes. When I had a few injectors go out on me, when I had my car, I fouled up the plugs pretty bad. I had one reading 17.2 the other 19.3. The others that were at 13.1 were burning normal. I think I read somewhere that the higher the resistance, the longer they tend to stay open. Either way, they need to be replaced, that will solve a lot of your issues.

If you are going to replace them, obviously newer style and might as well go to 740cc. You can tune them pretty easily.

[budget300zx]

As nissanfeak12 stated also could be the injectors, but should be easy to retest them without the corrosion. possibly in spec.

if the good injector has a badly fouled plug, i would still suspect another problem elsewhere.

[Bigred*]

Ya the larger injectors are definatly on the list of things to buy in the future, was just hoping to be able run the car on these for a while till I can afford new ones.. I will try to get around to testing the injectors this weekend, but being the utah supercar grandprix is this weekend might be kind of busy!
So here's where I'm at now, been messing with all the plugs just cleaning things and making sure they're working, also deleted my ptu sub harness which actually definatly helped the lower rpms..
Right now the car starts right up and runs strong in the bottom, here's what I noticed that I didn't before. I can get on the throttle and the car starts to sputter as soon as i start to boost, thats why it's a little different depending on what gear I'm in. But my boost gauge comes up right to the 0 then it sputters like I'm hitting a Rev limiter. Also i can smell lots of fuel in the air when it starts to sputter, and sometimes it'll backfire when I shift out of the sputtering, which not gonna lie, brings a smirk to my face lol.
I can down shift when im going faster and itll put the revs up at 5k and as soon as i try to give it any gas at those in rpms it sputters and won't do anything till it slows down more.. Even though it says it builds boost right to the zero I can hear the waste gates whistle on the turbo when I shift, especially in first gear. I'll retest all the things on the list budget300 listed, i imagine some will be different with all the new clean connectors.. Also still need to test the tps! thats the one I keep forgetting to check. Thanks for all the help guys

[budget300zx]

^with that being said^

99% sure your gonna be looking for a boost leak....

[budget300zx]

just to get a head start not the best method but you should have everything to do this



soap and water method of testing
https://www.youtube.com/watch?v=b3KmQenhWDY

otherwise id recomend a smoke test with all these conections it could be from.

sounds like its reading all the airflow from the turbos, but never getting the forced induction(above zero)

[Bigred*]

Thanks for the help budget! So I pressurized my intake system a while ago to listen for air leaks and i couldnt hear any, thats why I started thinking it was a sensor problem and not a leak, because I yanked everything out and tightened it back up just for the heck of it.. Well when you said you thought it was a boost leak I started looking into it again and thought instead of pressurizeing the system I'll fill it with smoke and see if i could find a leak, and guess what, I found it, and feel so stupid for it being so stupid

The smoke started coming out below my air filter, which confused me because I didn't mess with stuff up there, started looking around and found my bov had completely blown off!! So your not really going to hear a leak when it's an inch in diameter. Turned the clamp gave up on life, got it replaced and its running strong as ever! So excited to have it running strong, ive been trying real hard to stay out of boost but the few times when I let a couple pounds come on, wow! There's still alot of work to be done but today was a good day, thanks for all the help guys!