stumbling and choking after 5,000 rpm? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 01-11-2007, 09:41 AM   #21
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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.
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Old 01-11-2007, 11:25 AM   #22
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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.
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Old 01-11-2007, 11:45 AM   #23
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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.
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Old 01-11-2007, 11:49 AM   #24
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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.
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Old 01-11-2007, 11:51 AM   #25
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Where is the boost line to the FMU tied into?
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Old 01-11-2007, 12:08 PM   #26
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FMU vaccum line is "T" serial to the OEM FPR.
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Old 01-11-2007, 12:10 PM   #27
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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.
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Old 01-11-2007, 05:29 PM   #28
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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......****.

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.
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Old 01-12-2007, 10:28 AM   #29
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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?
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Old 01-12-2007, 10:34 AM   #30
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Is this something that has been slowly showing more symptoms?
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Old 01-12-2007, 11:11 AM   #31
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was about the same time as the stumbling and choke.
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Old 01-12-2007, 11:18 AM   #32
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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.
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Old 01-12-2007, 11:24 AM   #33
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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!!

Last edited by Mimime; 01-12-2007 at 11:37 AM.
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Old 01-12-2007, 12:01 PM   #34
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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.
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Old 01-12-2007, 12:08 PM   #35
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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.
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Old 01-12-2007, 12:26 PM   #36
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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.
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Old 01-12-2007, 12:36 PM   #37
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There is no problem going over 6000rpm when not in boost.

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

Last edited by Mimime; 01-12-2007 at 12:50 PM.
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Old 01-12-2007, 12:47 PM   #38
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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.
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Old 01-12-2007, 12:53 PM   #39
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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?
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Old 01-12-2007, 12:54 PM   #40
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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?
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