[mystk96]

ok so i admit its nowhere near a beast but what would cause my car to bog down on the 1st rev then die on the second rev (if done consecutively) randomly while free revving and what would cause it to feel like it loses fuel or spark after shifting into another gear (more so 1st-4th) also randomly


new fuel filter
new plugs (few months old)
new fuel pump
new fuel pressure regulator
new crank position sensor

the car pulls strong at full throttle

the orange boot on the return fuel line in the gas tank is taken off

(having trouble finding a replacement)

[manolith]

i have this issue on my mach1 when i pull to much timing. once i go over 23* it does not do it.. i only pull timing to spray.

[mystk96]

the only "performance" mods it has is a full exhaust and a cai with a pro m racing maf. and i cleaned the maf like the company told me to. and still nothing has changed.

the plug wires are new

[manolith]

Originally Posted by mystk96 the only "performance" mods it has is a full exhaust and a cai with a pro m racing maf. and i cleaned the maf like the company told me to. and still nothing has changed. the plug wires are new

why dont you try the stock maf? the maf loves to screw the computer up. YOU NEED to tune your car when you change the mass air flow meeter. by the way.. why did you change the stock one?

[mystk96]

the previous owner did. i never had an issue with the car until i let it sit for a week when i was out of town and it wouldnt start by replacing most of the parts listed above it started and now i have this issue.

i called the company for the maf and gave them the part number they told me the maf was made for a bolt on 4v or some shit like it

[manolith]

whats the size of the maf? look read this.
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The Mass Air Flow meter's calibration is equally important. In fact, having a properly calibrated mass air meter is the single most important factor that should be considered when choosing an aftermarket Mass Air Flow meter. The meter should be calibrated to match the flow rating of the fuel injectors, in conjunction with the PCM (engine computer) being used for the given application. A properly calibrated Mass Air Flow meter will result in a meter that generates an accurate voltage signal vs. the air mass entering the engine throughout the entire RPM range of the engine. If the meter you are using is not properly calibrated, the meter may "peg" (reach maximum voltage output) before the engine reaches maximum airflow, which will result in an inaccurate air/fuel ratio, causing a loss in horsepower, or even potential engine damage. In contrast, it may fall below the PCM's expected minimum voltage input at idle speed, which will result in the PCM entering a "failure mode", which will cause a very rich condition at idle. A properly calibrated Mass Air Flow meter ensures that the PCM receives a correct signal throughout the engine's entire operating range, resulting in a proper air/fuel mixture, maximum horsepower, excellent drivability, and maximum fuel economy.

There are various methods currently being used in the aftermarket to recalibrate Mass Air Flow meters. There is only ONE correct method. These methods are as follows:

One method being used manipulates the voltage signal from the Mass Air Flow meter by mechanically changing the amount of air that is permitted to pass by the filament of the meter. This is done by installing a different size sampling tube, or by restricting the flow through the tube with a screw. While this method can result in a voltage vs. air mass reading that is usable by the PCM, it is not possible for it to be correct throughout the entire RPM range. This WILL result in some form of drivability concern. These are commonly reflected as idle problems, loss of power, and poor drivability & fuel economy. Expensive and time consuming dyno time is highly recommended with this type of meter, and the results are not always consistent.

There is also a method of introducing a "Mass Air Flow Tuner", which is usually some type of in-line electronic device which is intended to vary the voltage output of the mass air meter to extend the range or allow the use of a Mass Air Flow meter that has not been properly calibrated. These devices will require dyno tuning to work properly, because the Mass Air Flow "curve" does not match that of your PCM. Since no transfer function information is available when using these devices, expensive and time consuming dyno time is an absolute must!

There is also the option of using a meter that has not been calibrated at all, or is not properly calibrated. See "Buyer Beware" below. Commonly, these meters have a generic curve that may, or may not operate within the appropriate range of the engine. These meters will require dyno tuning to work properly, because the Mass Air Flow "curve" does not match that of your PCM. Since no transfer function information is available when using these meters, expensive and time consuming dyno time is an absolute must!

The final, and BEST, method for calibrating a Mass Air Flow meter is to change the Mass Air Flow meter's voltage output by manipulating the electronics of the meter itself. This is an extremely accurate way to calibrate a meter because the meter's "curve" can be precisely targeted to reflect the needs of the new application. Pro-M Racing was pioneered in 1988 by Bob Atwood, a Ford engineer who was instrumental in developing mass air technology. Not only is this method based upon OEM techniques, this is truly the ONLY way to PROPERLY calibrate a mass air meter. Pro-M is the only aftermarket company with both the intellectual and physical properties necessary to properly calibrate your mass air meter. In order to properly calibrate a meter, you need to know the baseline "curve" of that meter. Quite simply, we are the only aftermarket company in possession of this information.

As an added bonus, All Pro-M meters are supplied with a transfer function sheet. This is the air mass vs. voltage data for your particular mass air flow meter. This is invaluable information for anyone who desires to have their PCM professionally tuned. It allows the tuner to have the EXACT air mass vs. voltage data for your meter, resulting in a perfectly accurate reading by your PCM. No other method of calibration will provide you with this important information. Lack of this information will result in a "tune" that is, at best, an educated guess.
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i got it right off Mass Air Flow Meters Facts : Pro-M Racing, LLC, Mass air flow meters for all vehicles

[DickH]

Does it idle fine?

[manolith]

oh do you have the maf screen?

[mystk96]

i appreciate it. idk the size of the maf. i dont have a stock maf for the car. would you happen to know how much a stock one runs

[mystk96]

Originally Posted by DickH Does it idle fine?

has a popping in the exhaust kinda normal i guess it sounds like a miss but isnt i asked a buddy of mine who has a 97 and he said his does the same. kinda like a irregular idle

Originally Posted by manolith oh do you have the maf screen?

i dont think. the only thing that gets me is it ran perfectly before i let it sit for the week minus the popping at idle

[manolith]

i dont know how much they cost.. but you say that it was running fine before. i heard people had issues with maf by just removing the screen. and also if the maf is not position properly.

[mystk96]

yea i heard the same... do you think the rubber boot on the return line not being on has something to so with it

[manolith]

was it like that before?

[DickH]

2v guys usually get away with cleaning/replacing the iac valve whenever there is a problem. You could give that a try.

[mystk96]

Originally Posted by manolith was it like that before?

no but it was so tender it crumbled at touch

Originally Posted by DickH 2v guys usually get away with cleaning/replacing the iac valve whenever there is a problem. You could give that a try.

already tried it lol

[2003MACHWON]

i had the same problem with my 03 gt. it would never die just bog down and backfire i replaced everything, plugs coil connector maf, idler pulley.. etc it would quit for a day then come back so i finnally got to the point and sold the car and bought a new one hopefully youll have better luck then i did