Slight Hesitating Issue!?!?!
 

Car’s been hesitating quite a bit lately at steady rpm cruising; hopefully someone can diagnose the problem or tell me where to start looking. It’s not a violent hesitation but very settle; be driving at say 50mph and you feel a little sputter (doesn’t 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)

This same thing happens to me.

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.

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.

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:

I also replaced the afm .

dont open it and fettle with it inside. whatever you do!

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.

You DO need to be delicate. This is not "hammer technology":gay:

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?

One note would be... I dont have an AFM and I still have the problem ;)

Tell that to all the folks running RX-7 AFMs :bigtu:

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

http://i25.photobucket.com/albums/c5...lei2006107.jpg
http://i25.photobucket.com/albums/c5...lei2006113.jpg

How was the result of the cleaning? Fix your issue? Just curious

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...

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?

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.

its still hesitating damn it in 5th gear at 70-80pmh!!!:vash: :vash:

what else can i check?

Fuel pressure, timing, etc.

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.

If the car's idle/closed-loop/low-throttle-application/engine-in-vacuum was affected by R&R'ing the Vortec FPR, then either it's broken or you have the fuel plumbed incorrectly. Cleaning the FPR shouldn't have caused the issue to get better or worse when driving in vacuum.

Oh, wait, you said it seems to work fine under WOT and/or once the engine's up to operating temps? Perhaps the O2 sensor is throwing some crazy values at the ECU while it's warming up? Although typically the ECU shouldn't even car about the O2 value until the car's reached a certain temp.

I guess my money's on base timing (perhaps it's too low...enough so to cause issues when in overly-rich warm-up mode) or something involving the FPR.

For what it is worth; when my 4 wire O2 crapped out, I went back to the OEM single wire that started out in the car in the first place. It is mounted right after the turbo in the RMDP. A couple of times recently I have just started the car and taken off cold and get all sorts of bogging, CEL, and stalling. It is definitely being made much worse because if I hit the slightest boost the Emanage throws in even more fuel because of the O2 signal being low or non-existant. As soon as the O2 heats up, everything is fine.

As posted earlier i have cleaned the AFM contacts, but i didn't tension the brush sliding over the contacts to much. And it made no difference. Now i have tensioned the brush a little more, this seems to work a lot better.

It's not the FMU's fault, it's the increased intake temperature's fault (ping)....Throw an intercooler on there, drop the intake temps, advance the timing.

If I had the cash I'd own it. Would you suggest purchasing a bipes first to advance the timing or intercooler and advance a little till I get a bipes.

Even at a low boost level with Bipes you can at least have a 10°, 12°, 14°, 16° base and pull to 6°.

This might be a possibility.

my car does it too.... it just hiccups while cruising at 70mph. It might do it once every 40 miles or so then fine. It just has one very short hiccup then back to normal again...

mines still doing it after all i changed.

I really am at the end of my teather.

Only thing I have not changed is the fuel filter and the Vortech fpr.

I am gonna go to the dyno to see what AFR's the car has.

I really feel like ditching the turbo at the moment.

stupid car.:vash:

Took it off and put in the plug! Ran around for a day no change... Check that one off. I set my o2 clamp to (.40) inbetween full rich and stoich a few weeks ago and that seemed to help some. Been messing with the the vac/boost switch and seems to stop doing it as much the later I kick in the clamp. Of coarse transition to boost then again sucks. Gotta be a combo of not enough timing and too much fuel. When the car heats up will burn all the fuel more effecently.