it runs! kinda...problems inside.

[Carl H]

Well guys i managed to finish up the exhaust work and get the car 'somewhat' drivable...on the first spin out we gently drove it around to be nice and easy on the clutch as it is fresh out of the box.slowly worked it up and eventualy got to the point where i felt that it could do a wot pull.needless to say the power delivery of this engine is fantastic, but we only got a short taste (only 2 2nd to 3rd to 4th pulls) of it as it started acting up after we stopped to chat with some friends.heres whats going on...car will start normally and runs great first start of the day, has no appearance of any problem whatsoever.at some point the car will begin to feel 'rough' and hesitant to accelerate, idle quality degrades and it will begin to hunt then stablize but still be a bit rough.under load and wot it will get up to around 3k and completely cut out, sometimes it will make it past 3k to 4k or even 5k but does not make power and is very hesitant.since it appears to present all the symptoms of a bad maf i swapped for a spare i had and problem persists, no maf code from the ecu.injectors have been ohmed out and they were all 14ohms +/- .3ohms after a short cool down period and around 13.5 across after a quick drive.i have not had the chance to check rail pressure but am stumped at what it could be.checking consult mixture appears to be lean at idle and all of the place at cruise, wot will again be very lean...not an accurate method but some idea of whats going on.any thoughts?

[tmorgan4]

I promise you I'm far from an expert on this, but it does sound eerily close to my scenario.

I chased this issue down for a long time. If I had to guess one thing (since you already changed out the MAF and it didn't help) I'd guess a vacuum leak.

Mine had the same symptoms. First start, it would idle and run great. Once it gets up to operating temp, it starts to run like crap. My reasoning for this is that during the open loop (warming up) it always runs extra rich. With all the extra un-metered air coming in probably runs about where it's supposed to AFR-wise. Once it hits operating temp and goes into closed loop and uses feedback from sensors to control the engine it starts missing and runs unnecessarily lean.

It constantly hunts for a stable idle which is a pretty damn good clue it's a vacuum leak.

I didn't follow in your build how far you tore the engine down. My main sources for the vacuum leak was 1) the plenum never sat completely flat on the lower runners because of a hose clamp catching on #6 lower runner and b) I didn't replace the rubber ring gaskets between the lower intake runners and the plenum.

I assumed they were always supposed to be hard plastic and wondered how they ever sealed. Then I bought some new ones and they're soft, bendable rubber! I replaced those, made sure the plenum sat flat, and amazingly....the engine runs like it should!

Definitely something to think about if you tore the engine down for inspection or rebuilds.

[npez]

Carl,

Are you running your EGR system? Just a stab but a stuck valve could cause the symptoms you mention. Just my $.02

Thanks,Nick.

[Carl H]

i am running an egr system on the car for maximum efficiency and mileage...and it is rather odd but during coldstart and for a good bit after it sounds very quite and idles like glass.however once it comes out of that it makes a 'whistling' sound that is hard to describe...i had thought of the egr valve being an issue but its terribly hard to pinpoint the noise; i'll try disconnecting the egr valve tommorow and see if that changes anything.it doesnt sound like a traditional vaccum leak but on shutdown you can hear and audible hiss like when you pull the line off of the brake booster.

[robb1971]

one easy thing that worked for me in the past is to get a can of engine start and spray plenum/intake joints one at a time.. when the engine starts to rev because it has sucked up lung full , you have found your leak..just a thought

[T45]

My first guess going by your description would be fuel pressure. Are you running the Q or TTZ fuel pump? I'd check pressure and filter asap.

[Carl H]

using a q45 pump...and yes i will be checking fuel pressure as soon as i can.was definately one of my thoughts, regulator might be bad...if i have to replace the regulator then i'll also remove the now redundant fuel rail dampener.

[XJared]

whistling noise is most likely a vacuum leak.

[Carl H]

solved a few problems today and think i have found the root of the issues at hand.whistling noise was due to the pcv system not being completely plumbed in, I had the pcv --> air intake tube blocked off on both ends but the pcv to plenum still connected so it i suspect was drawing air in thru the somewhat dodgy plug on the line leading to the intake tube.checked egr by disconnecting the vac line and by manualy actuating the valve, valve moves freely and smoothly with no indication of binding.fitting a fuel pressure gauge inline yeilded results instantly...rail pressure is fine at idle but any kind of throttle applied and it drops like a rock.quick test drive showed around 30psi at cruise and amazing fly like a brick nosedive to 10psi or less under full throttle.tested fuel regulator as an issue by clamping return line only to yeild same result with pressure dropping substantialy with free revving (no load).that being said i suspect that the q45 pump i fitted has gone bad even tho it *sounds* like it is working.any other thoughts?

[tmorgan4]

You aren't using a fuel pump controller out of a Q45, are you? What did you do with the fuel pump controller wires coming out of the ECU?

[Carl H]

no fpcm here, just removed the wires and ran the fuel pump trigger to the stock relay.

[tmorgan4]

I'd say if you were getting 12V at the fuel pump that the pump is bad.

EDIT: Did you also try checking fuel pressure on your cold start vs. hot start? Any differences?

[Carl H]

used to be that it ran ok on first start but now the problem is consistent regardless of tempature.the pump SHOULD be getting 12v as it is wired in as per stock and i am using the beast q45 110a alternator.the pump is VERY loud when standing outside of the car and is quite audible when inside the car, much louder than my bosch 044 700hp fuel pump i have in my s14.

[Carl H]

http://www.youtube.com/watch?v=TQbN6PVuaEsyou can hear the fuel pump in this video, sound of death?

[gs14racer]

Definitly a fuel issue, i had very similar troubles when my fuel pump died.

You have only a few possibilities, either you have the fuel lines inverted, your losing fuel pressure somewhere (ie loose hose in the tank etc, pickup came off the pump in the tank), the regulator is bad ( doubtful), or your pump is bad.

but there is a more stupid possibility, are you sure you have gas in the tank, i once chased down a horrible hesitation issue just like you described. I didnt have the fuel gauge connected and the tank was dry, the motor started and idled perfect just woulndt rev up.

Good luck

[Carl H]

i drove the car to the gas station and filled up the tank, so i know it has fuel in it and the tank is a 'new' clean tank so thats not the problem.fuel lines are correct as the car wont run with lines inverted.its most likely the fuel pump so its time to order one.

[T45]

I'd pull the pump and check the piece of fuel line that connects the pump to the rest of the fuel pump assy. If it's leaking in that assy you'll be low on pressure. Also, make sure you have about 43-45 psi at the rail at WOT. If you're only seeing 30 at idle and you have it wired up to a relay I would suspect a bad pump or a leak somewhere in the assy. You should see around 45 from idle to WOT with it wired up to 12V without a FPCU.