stumbling and choking after 5,000 rpm?
 

Hi would anyone know these symptoms and has the right remedy for it?

I've just installed an Vortech 12:1 FMU and 1.8 injector(clean and even flow).

Waiting to install Walbro 190hp FP, as soon as I could fix this problem.

First, what is your timing?

Second, how much boost?

10BTDC and 5psi boost

throw in the Walbro....your current FP may not be up to the task of fueling at a substained output. It's a 30min job to see if its the problem.

The only thing set me back from that is with my Vortech 12:1 and 140psi from Walbro, I dunno if that will blow my 1.8 injectors.

HMM... I wonder if the 12:1 is deadheading your oem fuel pump?

I ran up to 8psi with my 12:1 and walbro and 1.6 injectors. The pressure isn't the problem per se. It's how much flow you get at that pressure that makes your top end super rich. It's the o2 sensor or cat that can be harmed from being so rich. And maybe paint aroudn the tail pipe. There is no, or almost no, damage potential to the injectors.

12 x 5 + 50 = 110psi

Those injectors will be fine and can fuel around 190rwhp at 110psi.


Corky suggests 200psi is the safe limit for injectors under 50 Lbs/Hr, 100psi over 50 Lbs/Hr

Pull your timing back to 6 BTDC. You may be detonating. The OEM fuel pump will handle the 1.8's at up to 8psi if it isn't shot. Did you check your max fuel pressure? Make sure the Vortech is connected correctly and maybe open it to make sure you actually have the 12:1 disc in there(unless you got it new from GReddy)

hh
 

I hope this may look a correct installation for you guys? :bowdown:

yes it does. test the capabilites of your current pump...i fear it may be losing substained pressure flow.

OK.. .just spent 20 mins install the walbro... ! but the problem still the same, and now is comes in earlier before 5k rpm! AHHHHHHHHHHH!!

at half thottle, it was no problem up to 6k rpm... but WOT it chokes.

Could I be putting fuel in the system?

You sure you FPR isn't in backwards? Sounds like FP is going through the roof.

HI Jayc, does the photos showing my FPR looks correct?

Also, rev at stop the car seems to drop idle lower than usual.

Sigh......! After another day at the shop looking though the system and decided to put in another FMU with dose 44psi at idle. (just for a try) The problem still not solved. Adding to that, as adviced by Olderguy, I put my timming back to 6 BTDC.

3-4 rpm holding at 3 psi boost, and doesn't want to creep up. once around 5k rpm starts to stumbles and choke again.

What i might do tomorrow is take out the AFPR, retain the OEM FPR... install the EMB, than put that on the DYNO.


:vash: :vash: :vash:

these cars really suck sometimes eh?

More thoughts, could this be time for O2 clamp? Am I being intrupted by my Stock ECU?

hhmhmmmm....i dont have one either. but would this problem not have shown up way before?

I have been greddy turbo'd since 2004.

either the fueling is fucked.

My new o2 sensor has only been in 2 days and is going crazy on the AF guage.

somrtimes it just goes off na dcomes back on randomly and when i let of fthe gas.. really strange.

Tabs, if you're saying that when you let off the gas, the AF gauge goes off the chart lean, there is nothing odd about that. Maybe I misunderstood you.

no goes off the chart completely....not registering.

makes me think there is somthing seriously wrong!

That's what I mean...going so lean that it doesn't register on the gauge when letting off. That's normal for n/a, should be as well for turbo.

yeah, that's what's supossed to happen. Your seeing 20.9% O2. no fuel.


Mimime, is your crossover leaking? maybe a fuel leak? Jump F/P and GND, and then clamp the return line down. That will raise the pressure to about 120psi.

Thank Brianeack,

I thought about crossover leak, but I could not identify any problem with it. I'll see if I could get a gauge and test the fuel system under load condition. Reving it in neutrel till 7krpm was not enough... no problem there.

The dyno is handy for checking fuel pressure under load. Unfortunately, if something is messed up, thats the only thing you learn from it. The o2 clamp just prevents the ecu from going lean when you transition into boost. Your already boosting when you have your problem.

Could there be air leaking past the AFM? When the air flow is that high, maybe something is getting sucked in and creating a leak? I know, its a wild guess.

Where is the boost line to the FMU tied into?

FMU vaccum line is "T" serial to the OEM FPR.

take three seconds and see if the fuel lines or injectors leak under pressure....at least you'll know. (i've had mine only leak at 115psi, 100psi and no leaks)


then go out so a hydraulics store....spend about $4-10 and a gauge and fittings and watch how you fuel pressures behave under load.

got my plugs thru the post today (NGK's)

fittedthem this eve.

Te old ones were whire...not black as I had anticipated whcih means the car is running lean......SHIT.

Anyway took her for a spirited drive and there is no hesitation at ALL.

will see how it goes over the next few days before i get happy.

I h8 garage that think they know what they are talking about. they told me the plugs would be fine as htey have only been in their a year.

wont be going back to the said garage.

Another weird thing is... my idle seem to be dropping pass 400 rpm and struggle to get back to 800rpm point.

Could this be a vaccum problem?

Is this something that has been slowly showing more symptoms?

was about the same time as the stumbling and choke.

I've lost track of whether you looked at the AFM brushes. If you don't find a vacuum leak(or the nipple blown off the back of the intake manifold) for the idle problem, I would look there next.

The Large black nipple is still in place!

AFM brushes- I have never token the AFM apart, where could I find more instruction as to looking at the AFM brushes?

Thanks Olderguy!!

When the AFM signal is erratic, it can really play hell with an Emanage because the erratic signal must be constantly read and interpolated, using up processor time. If the brushes are loose against the contact strip, the voltage can drop intermittantly to -0- causing a flood of fuel with or without Emanage being used.

The black pad on top of the AFM can be removed by carving out the sealant around it and lifting it out. It is better to do this on a table with good lighting than in the car, but if readily accessable in the car, may be done there. You also need access to the flapper door to move it back and forth.

Inside, there is a wiper brush that moves along a contact strip as the flapper door is moved. These contacts can be cleaned with alcohol.

Then, there is a hex head screw holding the wiper assembly on the shaft that turns with the flapper door. This screw can be loosened and the whole assembly pushed down the shaft so that the brushes push harder against the contact strip. Tighten the screw, replace the black pad and fill in to re-seal it with either hot glue or rubber cement.

Sounds good, I'll give that a try tomorrow. if that fail. I might change another coil pack.

Since the problem happens everytime i push and stumbles at 4800 - 5200 rpm.

If you gradually get up to 4800-5200rpm with out going into boost are you stull having the problem? You could also try disconnecting the vac. line to the vortech when you do this, just stay out of boost!

Put of fuel pressure gauge in there before buying a new coil pack. I'm willing to bet the issue is too much fuel.

There is no problem going over 6000rpm when not in boost.

Once in boost, I can't even get over 3psi of boost.

So I doubt that you coils are bad right?

I'd be willing to bet the dead hooker that's in the trunk of my car that there is something up with the Vortech FPR.

I thought that at first, and used another FPR (linear FPR). Same thing happens, I will disconnect all AFPR, and just run the OEM FPR and see how that goes.

I'll be damned if both AFPR fails! great way to start off my year! sigh...

BTW... what it feels like when the car is lean out too much or wooping rich around 5000rpm range?

On the pump you pulled out, are you sure it was OEM?

It is possible that someone put in a larger pump before you got it and you are overfueling because of the 12:1 Vortech with what you thought was original and now with the 190lph HP.

What are the numbers on the pump you pulled out?

85psi ... it was stock alright!

Just trying to touch all bases

You can't imagine how much help and advice you have given, I can say on behalf of the members here and espeically me the great appreication for you contribution. Sorry if I put that in a bad manner. I am just very fustrated and tire thinking the possbilites of it going sour!

You NEED to get a fuel pressure gauge installed so you can see what is happening when you are in boost.

Or you could reverse the lines on the Vortech FPR and see what happens. I still think you are over fueling. After driving around in boost abit does the car smell like gas?

yes.. in fact it does, I thought it was the little left overs gasoline when I installed the WalBro 2 days ago.

Figured as much. You are probably dumping raw fuel out the tail pipe :)

When you changed to the walbro pump the problem got worse right, the stumbling came on earlier. Stronger pump builds pressure earlier, makes sense.

Using the 12:1 disc and the OEM pump you will max out pressure (85psi) at only 3psi of boost (in reality it is more like 70-80psi). As the boost climbs FP does not becasue the pump is flowing all it can. Now put in the Walbro and at 5psi you are getting 110psi of fuel. The 12:1 disc and the walbro are WAY WAY to much fuel, especially with the 1.8 injectors.

Why it did this with the OE fuel pump? Maybe you had a REALLY strong OEM pump and it was able to sustrain the higher pressure.

I bet if you could get a 6:1 disc you'd be in business providing the FPR you have now is working properly and is installed correctly.

Hope this helps.

I'll let you guys know once I take the AFPR out... tomorrow! if that's the case, I will get a set of 305cc injectors and install my EMB. NO MORE AFPR! dammit!

Get the problem sorted out and identified before you install the EMB. Adding in something else that is complex will just make matter worse if the car isn't running well before.

Just buy another turbo miata and swap parts. Seriously, my car stumbles bad at the middle rpms under boost at WOT, but goes great past 5K. I just figure there is too much fuel to get used until the upper rpms. Shows what I know!? It would probably be a good idea to diagnosis this while the setup is simpler, but I am basically doing the same thing, just switching to MS. Just don't have the car out of the garage yet to get tuned by a friend. The screwy idle does tend to lend itself to a vaccum leak. Spray something in the engine compartment and watch it get sucked into the leak. Just watch what you spray.

Did you go through the idle setting procedure after installing the turbo? Mine was way fucked and had to be fix initially. After that I still had to occasional idle droop, reset the idle speed again and haven't had anymore problems than I did when NA.

im still heading more towards vacuum leak and not fueling. Overfueling in boost will not cause his idle issues. and if anything stumbling/hestiating is more of a lean issue.

And I still want you to check for fuel leaks damnit....takes 2 mins tops, dont need a gauge; just a paper clip and a wrench.

You assume the idle issue is related.

Bullshit. When I was having the issue with a stumble right around 4000rpm it was from over fueling. If it was a vac leak why did the issue change and get worse when he added the Walbro fuel pump?

I've run a complete weekend on the track running 9:1 AFR and 170rwhp (I dynoed the day before)....no bogging/hesitation/choking, just less torque.

http://memimage.cardomain.net/member...97_21_full.jpg


It might end up being a fuel issue, but I dont think overfueling is the answer. Cause now with 115psi and the same thing, not worse, then i'd rule it out.

other things id consider: coilpack, wires & plugs, afm.

Brainack, I went out yesturday and clamp the shxt out of the line. for minutes I still couldn't find anything.

If could be how the fuel is being delivered and not necessarily how much. Although the quantity would certainly make a difference.

If it was a coil pack why does he see the problem at WOT (building boost) and not at 1/2 throttle (no boost)? Same with plugs? Wires? Afm? Not talking about a large amount of boost.

It looks to be boost related, and the one thing that is directly refrencing boost is the Vortech unit. Now a vacuum leak might show up at higher boost levels for sure, but it sounds like he's having the problem right at cross over to positive manifold pressure. Just went the FPR starts to clamp down on the return.

Car was fine (I assume) NA. So what did he change? A turbo (duh) and a whack load of extra fuel.

I'm not being argumentitive, I just don't want to poor bastard to go and replace plugs/wires/coils only to find out the FPR is label backwards or some shit.

Start with the basics, confirm what you've changed. :)

I don't follow. What do you mean?

Jayc, sorry... that was to answer Brainack.

Brainack, I just took out the AFM for a clean up and see if the brushes have good contacts.

I am still running with the linear AFPR, took out the vortech. I have not put in a fuel guage yet. might do it later today.

Let say I do not attach a vaccum line to the AFPR, will that disable its function?

It should. What AFPR is it? Dude you have to get a gauge on there ASAP, messing around with out some information about FP is almost pointless and absolutely going to be frustrating.

If any of those components has a problem, it'll be exacerbated when under boost.

Well then I guess the thing to do is throw a couple of hundred bux worth of parts at it. ;)