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Old 01-05-2007, 11:47 AM   #1
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Default Slight Hesitating Issue!?!?!

Carís been hesitating quite a bit lately at steady rpm cruising; hopefully someone can diagnose the problem or tell me where to start looking. Itís not a violent hesitation but very settle; be driving at say 50mph and you feel a little sputter (doesnít sound like a misfire) very lite jitter jitter jitter (gradual and most of the jitter feel is threw the gas pedal) will clear up and do the same again. Now if I drop a gear get on it seems to clear up. Anyone?!?!

Not sure if it's related but replaced the o2 sensor little while ago and seem to have cold start issues. Starts fine but sounds like the motors getting flooded and more you press the gas the more it dies. Then will clear up go again. Same thing if I get on it or get it up to operating temp doesn't seem to do it.

Dunno?!?! Maybe a bad o2 sensor, MAF, Coilpack, Something Fuel Related (Pump, Filter, FPR, FMU)?

Specs:
90 Miata 1.6L
Greddy Turbo Kit (stock)
TurboXS BOV (atmospheric)
Olderguys o2 Clamp
8.5 Magnacore Wires
Denso Plug (one step cooler that stock)
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Old 01-05-2007, 11:52 AM   #2
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This same thing happens to me.
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Old 01-05-2007, 11:57 AM   #3
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i have the same issue also.

garage checked it out to be a faulty coil pack.

changed coil pac and all seems to be ok for now.

i have not taken it for a long drive though yet.
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Old 01-05-2007, 12:01 PM   #4
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VERY good point tabs.. I have the same issue and when I hit the dyno the other day I was losing readings on my charts. Since my plugs and wires are new the people on site said it could be a coil pack. Braineack mentioned they have been known to fail on these cars.
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Old 01-05-2007, 12:06 PM   #5
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Hate to sound like a crusader, but open the AFM, clean the contacts and adjust the brush so there is more tension against the contact strips.
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Old 01-05-2007, 12:10 PM   #6
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Quote:
Originally Posted by olderguy View Post
Hate to sound like a crusader, but open the AFM, clean the contacts and adjust the brush so there is more tension against the contact strips.
I was wondering how long it would be before you posted that. :gay:
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Old 01-05-2007, 12:19 PM   #7
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I also replaced the afm .

dont open it and fettle with it inside. whatever you do!
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Old 01-05-2007, 12:29 PM   #8
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This is the same problem as what I was having when I first got my turbo installed. It turned out that I needed to open up the afm and clean the contacts, it will read in spec, until you tear it open and start moving the wiper along the rheostat, at that point the resistance values jumped all over.
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Old 01-05-2007, 12:39 PM   #9
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Quote:
Originally Posted by tabs604 View Post
dont open it and fettle with it inside. whatever you do!
You DO need to be delicate. This is not "hammer technology":gay:
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Old 01-05-2007, 12:40 PM   #10
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To those that have taken it apart to clean it. I have contact cleaner at the house I will try that. Got a pic of the brush to adjust, and how much to adjust?
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Old 01-05-2007, 01:10 PM   #11
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One note would be... I dont have an AFM and I still have the problem
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Old 01-05-2007, 01:40 PM   #12
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Quote:
Originally Posted by tabs604 View Post
dont open it and fettle with it inside. whatever you do!
Tell that to all the folks running RX-7 AFMs
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Old 01-05-2007, 03:11 PM   #13
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I am having issue's with the to much fuel aswell.
Olderguy mentioned to clean my AFR.
I took some photo's of the cleaning process


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Old 01-05-2007, 03:15 PM   #14
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Quote:
Originally Posted by andrepascal View Post
I am having issue's with the to much fuel aswell.
Olderguy mentioned to clean my AFR.
I took some photo's of the cleaning process


How was the result of the cleaning? Fix your issue? Just curious
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Old 01-05-2007, 03:26 PM   #15
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No, in my case it did not fix the problem.
So next step for me is to look at the O2 sensor which i did replace with a four wire version.
Maybe that is where my problem is...

Last edited by andrepascal; 01-05-2007 at 06:31 PM.
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Old 01-05-2007, 05:35 PM   #16
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I am installing a new 4 wire o2 sensor.

If after all this its not cured apart from cursing I will be looking at the Vortech FPR.

As this may be faulty!

How can i check the Vortech FPR is fucked or not?
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Old 01-05-2007, 05:40 PM   #17
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Throw a FP gauge on it and see how it reacts under boost.

should be:

35psi at idle.
50psi at 0~hg. (recreate this by removing vacuum line to FPR)
With the 12:1 vortech the FMU should hit your max FP output at full boost while driving.
or written as 12 (ratio) x (boost) + 50 = PSI

To test the output of the pump:

Turn your Miata to ON but do not start it. Open the diagnositics box and put a paperclip on F/P and GND. That will run your fuel pump. With a pair of pliers, squeeze the return fuel line shut that connects the FPR to the original fuel pressure regulator. When squeezed shut, the pump will be forced to maximum output.
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Old 01-07-2007, 08:37 AM   #18
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its still hesitating damn it in 5th gear at 70-80pmh!!!

what else can i check?
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Old 01-07-2007, 11:38 AM   #19
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Fuel pressure, timing, etc.
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Old 01-07-2007, 09:28 PM   #20
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Well got some time today to take the AFR out an clean it. Looks brand new inside but clean it anyways. Took it for short drive and seem to be worse. Cold start issue deal again. I sat and the end of the neighborhood tring to clear it up. If I touch the gas the rpm's drop almost to die instead of going up. If i sit there and get it out of the stumble and hold the rpm's steady at 2.5k or so it's intermittend. It will start to do the stumble drop rpms, come back up. Just putt it in first and nailed it high rpms or full throttle pulls i have no problems. It's gotta be timing, but don't understand why greddy would provide a FMU that would flood the car due to the retarted timing it calls for. Then again maybe i'm wrong.
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