Ok, i have tried searching, and iv tried everything i can think of but it still wont run right. The problem is: the car will start most of the time, and some times it will idle, but very poorly. other times it runs for a few seconds then drops revs and stalls, and there is nothing you can do to keep it running. when it does idle, it wont rev up very much before it starts sputtering and tries to stall. i can get it all the way to the red line some times but it wont stay there for more than 2 sec. after running it for a few min the plugs are usually so foul that it wont even start again, and il have to clean them before it will even fire (clearly running rich as trump). now here is were it gets frustrating.

Mods on the engine:

-first off its a 92 engine, tranc, harness, ecu, and all engine related stuff. but it is in a 95 240sx body, with all its stock interior wireing and what not, so there was a little bit of grafting to conect the 92 engine harness to the 95 dash harness but it was purity strait forward.
-Arias 8.8:1 pistons
-twin 248 exhaust cams (intake at 3 teeth off)
-370cc sr injectors (all work great and dont leak)
-adjustable fpr (iv tried it every were in its range with no luck)
-blow trough maf set up (stock sensor, on cold side after bov)
-egr/emotions control delete
-butterfly valve delete
-top mount turbo header (custom fab)
-Ct26 twin scroll turbo (internally gated)
-Megan down pipe with new ngk O2 installed
-reworked vac system (have one big hose coming from my manifold to a 3 way vac manifold, to bov, boost gauge, fpr)
-all silicone couplers and bolt clamps
-biggest fmic i could fit on it
-enthalpy ecu
-moved battery to trunk
-moved pcv feed from the intake runners to preturbo (i blocked the stock nibs on the bottom of the runners and used the 4 way splitter for my vac system)


Things iv tried:

-known to work maf (also tested with multimeter)
-new plugs (ngk iridium)
-2 different dizys (tried moving it a tooth in either direction also, and timed with a light of course)
-pumped the intake up with bike pump and sprayed it down with soapy water (no apparent vac/boost leaks)
-cleaned iacv (moves fine, seems to work)
-added four 1/4" grounds to head and block
-pulled fuel rail and watched it fire (no leaks no sticky injectors)
-checked fuel filter for flow
-adjusted fuel pressure everywhere from 5-40 psi (made no diff that i could tell)
-new knock sensor (have a few, the new one trows a code so i swapped in a used one and no more code?)
-new tps (adjusted to .5v at closed)
-tried 2 different temp sensors
-bled the coolant
-adjusted idle screw throughout its range
-checked idler timing and cam timing
-tightened exhaust flanges
-continuously looking for shorts/problems in my harness
-probably more, iv been throwing everything i have at this thing for 2 months now with no improvement what so ever
-pulled larg clumps of hair from scalp, wasnt the problem...

What does the motor compression test at? If I remember right, with the 2 exhaust cams its supposed to be 4 teeth off.

Haven't done a compression test, but its got brand new pistons and rings and the cyls were right on spec when i built it so i am asuming its all good, i will test it though. I read on a few forums that 3 teeth off or 4 teeth of will work. The difference is 4 teeth or is .5 of a tooth retarded (resulting in a loss of low end power and a gain in high end), and 3 teeth of is .5 of a tooth advanced (resulting in a large gain in low end power, and the high end stays about the same as stock). since its turboed i figure the boost will take care of the high end power so i used 3 teeth off hoping it would be less lagy in power and possibly spool up faster than if the power band didn't come tell higher rpm. Let me know if that makes any sense hahaha.

Pics of IC pipe setup may help. IACV hooked up?

Enthalpy ECU setup for the injectors and MAF you are using?

No mech fuel pressure gauge to see what FP you are actually at?

The iacv is hooked up, i did email my set up to Jason at enthalpy. It did this even with a stock ecu though, but it was a lot smoother when it was running, and there was no way to keep it running for more than 5-10 seconds.
There is a mechanical pressure gauge on the fpr but i dont know how els i could test it.

FP reading 34psi at idle then?

Now I'm confused at the fuel setup. Take a pic of how the hoses are running from fuel filter and through the rail/FPR and return line.

I see the one line on the intake going to Valve Cover, where is the other line going to? If to the intake mani that is unmetered air.

What's the rubber hose going in front of the engine to the middle of the turbo(between exhaust/compressor housing)?

Looks like the MAF is right beside the BOV, that definately wouldn't be good after running. Not sure if it would affect it idling though.

i dont have a pick but it goes pump-filter-rail-fpr-return. The smaller hose on the intake goes to the pcv valve. The other two hoses going across the front of the motor are the coolant lines for the turbo. the MAF if right after the BOV so no metered air escapes when its open.

Haven't seen anyone do that with pcv, would it be causing any vaccum leak?

Some kind of vaccum leak would be my bet if the ECU checks out.

The BOV right at the MAF will be disrupting the flow through the MAF though. Normally a MAF is in a straight section of pipe with 4-6 inches on each side of it. Most blow-through would have the BOV on the hotpipe.

ya i might try that. i did try putting the maf on the intake and it made no difference.

knobep wrote:ya i might try that. i did try putting the maf on the intake and it made no difference.

Yeah the MAF issue will show up more when running on throtle instead of just idling.

I tried the idle screw just about everywhere in its range but it didn't seem to make much of a difference no matter were it was. (started all the way in, and moved it 1/4 turn at a time tell it was all the way out.) sill idles like s***, at about 400-500 rpm and shakes and misses.

I'm moving this to KA-T section, should get a few more replies.

Much appreciated! i forgot there was a dedicated forum for ka-t, haven't been on in a wile.

im going to try it with the stock injectors and fpr to make sure thats not my problem.

If going to stock injectors you'd have to go to stock ECU and MAF as well.

well it is the stock maf and ecu, there is just a daughter board installed in it.

But its Enthalpy tuned correct? Its set up for stock maf and 370s?

Its supposed to be. but i have no way of telling if its tuned correctly. I ordered an ecu talk consult to usb cable that supposedly can be used kina like a AFC to adjust fuel mix and timing electronically. not sure if it actually re flashes it or if it is just temporary and goes back to normal when unplugged. hopefully it will at least help me track down the problem. I did try it with the stock ecu before it put the rom in it and it ran smoother but would only run for 10 sec max, and wouldn't rev up at all. It didn't through any codes though...

Your ECU vs MAF may be the issue. I've not heard of Enthalpy tuning for Stock MAF, would almost guess it is for another MAF. If it wouldn't rev that MAF may be bad as well.

Its a known good MAF, and it reads fine with a volt meter but being tuned for the wrong maf might be part of the problem. However it still didnt run right with a stock ecu.

is your ecu an s13 or s14 ecu? I almost bet its tuned for a stock maf just not the s14 stock maf, toss an s13 de maf on her.
any tuner can make a stock afm/370 tune. Tunes go smoother imho when you do maf/injectors that bring the k value back into near stock value.

if the s13 maf doesnt work then return the car to stock, diagnose that way.



how did you check thing if it would not idle on its own?

its an s13 ecu, motor, trance and all of the engine electronics, sensors and wiring are all s13 as well. The project started with a s14 body with no drive train accept diff and shaft, and a doner s13 with a totaly working drive train (was my daily driver up until then but the body was rusty as hell). so everything engine related is out of the s13 and is purity much independent from all the rest of the car.

PS. returning to completely stock would require another total rebuild, not really practical. with the daughter board installed it will idle, just wont rev at all and is really rich and rough. with a stock ecu it wont idle for more than 10 sec before it stalls, and still wont rev up much, but it is much smoother and not as rich.

if a daughter board is installed the ecu cannot be considered stock unless you move the jumper at cj2 back to cj1. You cant just take the chips out and its stock ecu again.

if you continue to try running the motor this way you will be rebuilding it again... sure a motor runs at a 10:1 afr however the oil gets diluted extremely fast resulting in bearing failure.

Is the timing right? verified with a timing light and you are sure it was in the timing set mode?

any codes?

I started with a stock ecu, then installed the daughter board and moved the jumper from cj1 -cj2. (thinking the lack of a tune might be the problem but it didn't help much as you can tell). Before i put the DB in i went though the codes and had MAF and knock sensor codes so i got a known to work MAF from my buddy, and switch the knock for another fairly new one i have (the one i had on it was brand new), any way after i switched them the codes stopped coming back but the problem didn't change. (start fine, sound good then it would try to idle down to 750 and just keep going to 0. and it seemed like anything i tried to do to keep it running just made it stall faster. I was stumped then and the only thing i could think to try was putting the DB in and see if the tune fixes it.

PS. timing is set at 20 btdc checked more times than i could count, and the tps was indeed unplugged. the strange thing is that the dizzy wants to be all the was retarded to be at 20 btdc, i have tried 2 different dizzys (no change), and have tried moving the base timing a tooth but then it has to be all the way advanced to be at 20 btdc.

One thing i have considered is that its because of were my O2 is located. i have it in the 3" down pipe rite after the turbo, and stock its in the much more restricted end of the manifold.

Another thing i haven't tried yet are new plug wires. i couldn't find any in the stores around me so i ordered some, but they haven't arrived yet. could they cause something this sporadic?

Anyone one here from Halifax?

Update: i took my fpr apart and cleaned it out and now it seams like the pressure gauge bounces down then back up really fast every time an injector fires, so im feeling it might just be a fueling problem. im going to try a different pump and run some injector cleaner though it to see if it gets any better. if not i guess im going to have to suck it up and buy new injectors.

Update II: was messing with it a bit today and decided to leak test my intake system again, this time i plugged the intake at the turbo inlet and used a bike pump to fill it up to 15 psi. i found a few boost leaks of metered air (one was from the top of my MAF were the silicone had lifted) and one vac leak from the adjuster screw on my fpr, which i just raped some teflon tape around and put back in. Now it will idle "OK" and pull a bit more weight on the road but still wont take much throttle. It will rev all the way up in neutral/clutched, but if i open it up more than about 1/4 - 1/3 load or no load it just back fires like crazy. I did have my eprom tuned for around 10 psi, and im only running 5 right now because it is still newly built and not fully broken in. could it just be riching out because its tuned for more boost and isn't getting it? also it sounds like its running on 3 cylinders but unplugging any individual spark plug or injector seems to have the same effect on it (not much, slight drop in revs but little difference in roughness).

Update III: I have traced the problem though the entire harness and all the way to the daughter board, which i assume got toasted when the old ecu got shorted out. The ecu itself seems to be fine because this one was never wired wrong. Here's hoping a new DB and tune solves the problem once and for all.

Update IV: I got it running perfect as long as i keep it under 7 or so psi now. My consult cable showed up and it pointed towards a bad maf connection so i sanded the pins and crimped the things in the plug a bit tighter and timed it again and now it is no longer in safe mode but since i destroyed my daughter board wile removing it i had to order a new one (yet to arrive) . thanks for all the help with sorting stuff out. i guess its just down to a tune now.