Confused by sudden loss of power

[mentordrift]

I'm not entirely sure what's happening right now with my RB25 in my S14, but it seems like I am suffering either a HUGE non-detectable boost leak, my fuel pump is taking a major $h!t on me, or I have a faulty ignition switch.

What happens is the car will run fine earlier in the day, like around 7 am, and will run fine when colder in the operating temperatures. But when ran for a longer amount of time, usually around 15-20 minutes, it will unexpectedly lose power - as in; pushing on the gas pedal, no response.

A flick of the key from off to back on will correct this - without having to turn the key to "start" - like if you turned it "off" then back "on"

Then, the car will not boost higher than around 1-2 psi, it will studder and hesistate severely when trying to boost any higher than that.Then suddenly, the car will act fine again, boosting happily to 10-11 psi, no breakups in power, no nothing.

At first I thought my MAF sensor was going bad, but the symptoms aren't consistent enough, and I can rev the engine well past 3,000 rpms when not getting into boost WHEN the problems occur. When the car isn't having issues, the car rev's happy-as-a-clam

Then I thought - maybe a boost leak? I checked all of my intercooler piping, and gave a quick visual to the vaccuum lines around the intake manifold, but didn't spray them with soapy water or use a compressor to test YETBUT this doesn't make sense either because I will be able to hit boost, and then suddenly not, and then again, be able to hit boost again.

I have been checking things off as I go along:-Ignitor is good-Coil packs are good-Compression check at engine install was all positive with zero leakdown-I haven't checked the plugs yet, because I work just long enough to have no time except on weekends.-Fuse under the hood for ignition is good, also new - but I did have electric fans hooked up to it at one point; also just prior to having these problems did I remove them and connect them elsewhere they are FAL 220's on a Mishimoto radiator.-Fuel injectors are all firing as they should, when the engine is turned by hand they do what they need to do, blah blah.

I have a Nissan Quest alternator and a optima redtop battery, but the battery holds a solid 13.9-14.1 volts even when power cuts out. The battery cables do not have any frays or tears that are grounding the positive side either.

As for the possible boost leak or turbo problems, the only places I haven't really checked good are the BOV (non-recirculated turboXS H-RFL), most vaccuum lines at the firewall, and the boost controller/wastegate area - only because those seem like the car would barely run at all if that were the case.-Would a good check be to replace the h-rfl with the factory recirc. valve, and see if it cures the problem?-Is the turbo possible damaged somehow? Some kind of debris, or SOMETHING that is causing intermitent....****ting on?

As for my fuel pump...I am prepared for flaming on this one:It's a stock S14 fuel pump, but it is under 2 years old. I know that I shouldn't be running it, even at all - but is it possible that the fuel pump is actually starting to get lazy and I am having fuel starvation problems where there is very little fuel pressure?

Then the ignition switch: I have always had a blinking airbag light in my car, even before the RB swap took place - and I am pretty sure that some backwoods mechanic replaced that switch, because it just doesn't look right - the cylinder is....too out of place? Could a faulty ignition switch be sending a bad signal to the ECU and confusing the hell out of the car?

I know that this is ridiculously long, but I just spent the last few hours searching the forums for similar symptoms that others have had - and I have a combination of them!At this point, I want to take this slowly, bounce my ideas off of the guys (and girls?) on here, and just figure this out once and for all!

[Coolwhip]

i read, 3 words... stock fuel pump

TISK

I'll read the whole post now

[mentordrift]

i read, 3 words... stock fuel pump

TISK

I'll read the whole post now

I know That's getting changed asap when I get paid.

[ANVIL]

yeah grab a walbro 255 they are like 100bux everywhere. dont forget to get a fuel pressure regulator, and probablly a fuel pressure gauge. i like the nismo adjustable fpr and i have a summit racing inline fuel pressure gauge.

[mentordrift]

I picked up a nismo fpr for like $80 a while ago.

a quick update:

This morning driving to work:-No problems AT ALL.

driving home from work:-No problems AT ALL.

[WhatsADSM]

When you are driving and it looses all power...

Do you mean it hardly drives at all, or that it still drives fine under no boost but when you get into boost it breaks up?

[mentordrift]

When you are driving and it looses all power...

Do you mean it hardly drives at all, or that it still drives fine under no boost but when you get into boost it breaks up?

Both, actually.One would be easiest for you to get into your car, drive a little bit, then while in gear and driving, just shut off the car.The other would be the boost is really "choppy" when it gets there and studders really badly.

[SullivanRacing06]

Both, actually.One would be easiest for you to get into your car, drive a little bit, then while in gear and driving, just shut off the car.The other would be the boost is really "choppy" when it gets there and studders really badly.

yea deff on the stock fuel pump sorry but doooo slap to the back of the head for you lol, jk, but yea 100 buck upgrade aint to bad?? and add so engine groungs as well, no iff back yard bob installed your ing switch then go ahead and pull your plastics of your colum and check to see if there are ne wires spliced together or just loose, good luck bro, ****ty to hear sum lik ethis happen

[arauz]

are there any misfires in the loss of response?

[WhatsADSM]

Yea I would definately check the ignition switch first... although it is a little strange that it would happen only after the swap.

Other than that I would check the wiring on the MAF and the CAS sensors. (Almost sounds like you might be missing cam sync or something).

[mentordrift]

are there any misfires in the loss of response?

Nope, the rpms the fall really slowly unless I "restart" the car.

Yea I would definately check the ignition switch first... although it is a little strange that it would happen only after the swap.

Other than that I would check the wiring on the MAF and the CAS sensors. (Almost sounds like you might be missing cam sync or something).

The car did have a few issues with the starter/ignition when I had the KA24 still installed, plus the airbag light - which I have heard can be linked to an error in the ignition.

What is Cam Sync? I have never heard of that, but it almost sounds like it would be one side of the engine would be moving at a different speed than the other side? I'll have to follow the wires for the MAF and CAS, but both have voltage and checked correctly when I checked them for continuity, but I didn't check my actual CAS unit. I honestly didn't even think of that based on what was happening with the car - could be a timing issue? There was a small wire that kind of irked me in the harness on the was to the MAF that made me nervous though, it was a bare wire that I soldered and shielded as best I could and made sure wasn't grounding or touching other wires.

I'll check the timing itself to see if it went WAAAAY off for some reason, then inspect the CAS and connections there also and let you know.

[mentordrift]

Alright, this is starting to look more and more like a MAFS problem now.

I didn't get a chance to get into the car today as much as I liked, but I did get to get a few things off of my list...

After having the car have another problem AGAIN of losing power, I decided not to turn the key off and on and to just coast along as the RPMs dipped down, and noticed that the car will come alive back on around 3k RPM in 3rd gear if the car loses power around 4k RPM - keeping in mind my Tach. is not recalibrated yet.It does NOT do this all the time.

First off - I checked all of my vacuum lines to my boost controller (manual, hallman pro), all of my intercooler pipes and their respective couplers, and a few misc. vacuum lines (like the brake booster lines, etc). Only a few seemed very loose, and only one is going to require a good effort to get to and adjust.

Also, before I ran out with the car on a diagnosis run, I took off the air filter - one; because it's a cheap ebay piece of crap and I remember someone telling me turbos don't like not being able to suck air, and two; I wanted to check the MAF sensor.

So, with air filter off and misc. pressure lines tighter than usual, I took the car around the block:First thing I noticed when I started it - My once non-working-for-whatever-reason-Faze-air/fuel-rice-gauge was reading now. wtf?Also, the car hadn't been sitting for very long while I was making my adjustments to the lines and pipes, but it was running hardcore strong. A lot better than before, like before it was all of these problems started happening in the first place.So here I'm thinking, "This is GREAT, it was that $h!tty airfilter" and went along boosting my way home... I turn down my street, and boom, the car has a stalling issue like it is having a boost leak again, where it sounds like the turbo spools then just kind of drops off into oblivion, and loses power, then regains power around - yep, 3k RPM.

No previous issues the ENTIRE time I was driving for a good 20 minutes, and then all of a sudden it has issues. So I drove it around the block again, to see if it would go away, still nothing. So it hits me - I turned the boost back down to stock 7 psi, and the car ran pretty much like a champ. Still a few hicups, and I'm waiting about an hour now to take the car back out to see if it's a fluke

I'm thinking that somehow the MAF is shorting out at higher boost levels, or my wastegate might be getting stuck? Does that seem to make any sense, because I have started keeping track of what happens when, just so I can see if it's an intermittent thing, or what.

[USMCgetsome]

yes sir definitely sounds like a failing maf. I had the same issues as you did. I had a failing fuel pump, failing maf, intermittent stuck stock wastegate. I first changed the maf. That stopped the stalling and motor shut off. Although if i was in 3rd or high enough in second i was able to do a down shift and it would come back on like a push start. The fuel pump also screwed me and it would cause a very noticable pause in rpm then come on strong the rest of the way to 7000rpm +. Also, due to both of those i kept thinking my timing was off. So i'd check then recheck.

Ohh and the bad maf will stay bad no matter what. I cleaned it check it's resistance. Would do fine for a few mins of driving then just degrade when temps got normal.

Check to see if your getting compressor surge! the TIS TIS TIS at low boost. Should tell you if your wastegate is failing or if your bov is too hard.

[mentordrift]

yes sir definitely sounds like a failing maf. I had the same issues as you did. I had a failing fuel pump, failing maf, intermittent stuck stock wastegate. I first changed the maf. That stopped the stalling and motor shut off. Although if i was in 3rd or high enough in second i was able to do a down shift and it would come back on like a push start. The fuel pump also screwed me and it would cause a very noticable pause in rpm then come on strong the rest of the way to 7000rpm +. Also, due to both of those i kept thinking my timing was off. So i'd check then recheck.

Ohh and the bad maf will stay bad no matter what. I cleaned it check it's resistance. Would do fine for a few mins of driving then just degrade when temps got normal.

Check to see if your getting compressor surge! the TIS TIS TIS at low boost. Should tell you if your wastegate is failing or if your bov is too hard.

I am almost absolutely positive now that it is a combination of the MAF failing and my fuel pump just getting a bit lazy. As you said stalling and motor shut off - I have the exact same thing: So what did I do after I turned down the boost tonight to double check? I drove around and got the temps up and bam, hesitation like you wouldn't believe.This got me thinking - if I unplug my MAFS, the car will still run, and if the car will still run with the MAFS unplugged, the symptoms will be IMMEDIATELY present once I get into the RPM range I have trouble in.So I get to a nice safe area (I.e. - my home), shut 'er down, unplug the beast, and get it running.And what do you know, about 4k rpm, it starts to have studdering and hesitation issues until it falls back down to...you guessed it 3000 RPM!!!

Also, with the "down shift for a push start", I have the same thing, but if I up shift from 2nd to 3rd, or so on, I can keep the car alive now, and luckily it doesn't seem to fail at all in 4th or 5th gear.

KUILLIN_DRIFTER

This has helped me very much, since you seem to have nearly the exact same problems as I have......now the question is where can I get a GOOD maf sensor? lol

Luckily, I'm not getting any compressor surge! That was one of the first things that I checked today, because a buddy of mine had a failed wastegate...then a failed engine...

[USMCgetsome]

lol. Took me about a year to trouble shoot all of that crap. lol. Everything was soo intermittent. Then the maf just took a complete crap. Exchanged with a new one and it was right as rain. Fuel pump was strange. Worked great at idle and normal driving. I'd get on it and bam! then it would start up as if it had fuel starvation. Had no idea what caused it. So i cleaned out all the fuel lines. Then changed fuel filters and cleaned out fuel tank. Still nothing. Changed out fuel pump due to loud whirring noise. noticable fail. Took a year for it to do the whirring. Sucked cause i thought it was all wiring. So i redid the wiring completely.

man i hated my engine. Got that all fixed and guess what. Ran like a damn champ. Then i sold it.

[mentordrift]

Hahaha, I spent nearly ALL last weekend tracing wires and soldering and doing my wiring and checking this bird's nest mess that was in there...it's still a bit messy, but man do I have an understanding of what goes where in my engine bay now. Next step I think is a good wire tuck when I have the chance since I know what I can cut and extend haha.

I totally hear you about the intermitent crap. I went literally two days back and forth from work without a damn thing happening with my car - no jumps, stalls, shakes - nothing! I thought maybe a spider or something got caught in a hose somewhere and finally got launched out lol

I'll have to let you know once I get my new(er) MAF in what happens, because as it sounds, this is exactly what is going on.

I went from ignition, to fuel, and now to MAFS....don't you just love RB's? lol

[mentordrift]

Okay, I guess I might be a LITTLE confused as to what a failing MAFS can make a car do. I've got a new(er) MAF on order - the lovely J60, wooo.....

My car still feels like it has a boost leak at times, even though I pressure tested and did a soapy water test just incase.

The turbo spools normally, but on occassion it will sound like it will just drop off and not want to boost any more, like it will stall out about let's say 2 psi. The problem I feel the most with the MAFS is a studdering/pause in RPMS at 4k rpm.

Are these two related, or am I just so anxious to get this fixed that I am making weird mistakes?

[USMCgetsome]

very related. car will bog and attempt to shut off. Or will just die while slowing down for a red light.

[mentordrift]

Okay.I'm just nervous about this stuff, is all. After a 3 month ordeal getting the engine INTO the car...yeah lol.

Anyway, I await the FedEx man

updates to follow.

[mentordrift]

Okay, i'm just self updating so I don't lose this in the recent topics...but cleaning the MAF I have made the problems get less severe than they are - they still occur, but less often.

FedEx is slow.....

[USMCgetsome]

tried to do the same back in the day. Sprayed electrical contact cleaner and sprayed away debris. That's all. Same issues as your stating. Replaced maf mucho bueno afterward.

[mentordrift]

alright, I finally got the dang MAF in the mail today, unfortunately it's raining a bit right now - so I'll probably be doing a late-night sensor swap.

at least this one "looks" a bit cleaner than my old one. It doesn't look as...beat up, I guess. That's a good sign?

[USMCgetsome]

get your butt out there and put that thing in! takes like 2 minutes. lol.

[silviasgp06]

if its not the MAF like the guys have been saying. it all sounds like what i went through.

sometime once the car warmed up it would not want to make power.I narrowed it down to the ecu. the rich ritard crap was majorly kicking in.

just a thought, good luck

[mentordrift]

The good news:

it would seem that the new MAF cured my ailing woes. I took the car once around the "block" and got it into boost several times, a couple of those times through 5th gear (my "block" includes a freeway).The car didn't stutter and stall, and it even held power when the fans came on! yay!

When starting the car, it held rpm's better than it was, and it didn't have that sound like it wanted to die - a good sign.

The bad news:

when trying to do some clean up work I popped a 75 amp fuse under the enginebay fusebox and now I don't have dash lights, radio, dome light, turn signals, radio, etc etc lol. But I do have headlights and the car runs!

I will be taking the car for round 2 in the morning, and getting myself a new fuse

[USMCgetsome]

it's pretty hard to burn out one of those big fuses. What the hell did it ground to? Investigate that before u take it driving again. Very scary!

Man i knew it was the maf!

[mentordrift]

Fixed the alternator issue...just a n00b grounding thing...won't be doing that again...

And good news! I drove from my house (east side cleveland) to sheffield Quaker Steak and Lube today for a small Nissan/Infinti meet with the car and the new MAF installed, and didn't have ONE ISSUE.That drive is about an hour, mostly highway, and before I got this worked out, I couldn't rev the car to those speeds!

HUZZAH!

Kuillin_drifter, I owe you a beer.

Hell, I'm even writing this down just in case...

Btw, does anyone know what the limit is on one of these J60 MAFs? Just curiousity hunting a cat.

[USMCgetsome]

i think your talking about a q45 maf. If so then keep in mind you need a SAFC or Power Fc to fun that maf. Stock puter will not run it. I think those are used for over 300hp

[mentordrift]

Oh no, haha, sorry that was a bit of a confusing question. I'm just curious what the horsepower limit is for the stock RB25 MAF. It's a series 1 engine, and thought it was a J60, but I could be mistaken.

[mentordrift]

3 days later and no signs of any of my previous ailments cropping up at all!

Case closed?