Any help would be appreciated. I've run out of things to check.

This will be a long message. I'll state the problem up front and then list what I've tried/done.

Sputtering (multiple times) at lower RPM (1000 - 3000) during medium to hard acceleration. Occasional sputtering (one time) during acceleration from 4000-7200.

2001 SE
30k
FM II turbo kit still on (without the Turbo installed)
Stock intake air system back on.
The modified intake has the 4 new injectors. I've disconnected the wiring to the new injectors.

I had the FMII system on my 2001 Miata for 2 years until about 10/07. I had to take it off to get the car smogged. (it passed). But since that time, I noticed a sputtering problem with it.

I noticed the problem 2 or 3 times when the Turbo was on and the car was
under boost. But it wasn't reoccurring so I just observed it. However,
since I took the turbo off the car, the problem occurs rather frequently
especially while cold.

The problem is reproducible when at low RPM's (2000 - 3000) in a high gear (5th or 6th) and part to full throttle. It feels like the engine cuts out then comes back to life usually with a loud backfire. It can do this four or five times. During this time, the car is still accelerating (slowly). If I lift off the accelerator pedal a bit, the car will accelerate normally.

But it does not do this all the time. On the freeway, I was in 6th gear,
cruising around 80 mph and floored it. I brought the car up to 100 with
no problems. Also, if I drive the car normally (no fast acceleration) it
seems to behave normally.

The car idles normally and has passed smog. I saw the technician hook up
the OBD-II connection and there were no codes present during the smog
check. The check engine light is not on. I swapped the turbo with the
original exhaust manifold, put the old exhaust system on, but left the dual
pipes on. I also borrowed an OBD-II tester and hooked it up. There were
no primary codes present. I used the menu system on the OBD-II tester
and drilled down and found a pending code of MISFIRE.

Since the time of the last reading, the check engine light has come on. I read it and it returned a code of PO131 Sensor circuit low voltage. Bank 1 of 1. I replaced the front O2 sensor. This was 3 months ago. The check engine light hasn't come on again. I bought a OBDII reader/datalogger and have checked for pending trouble codes but haven't seen any.

Recently, as I was doing more research into this issue and getting desperate, I replaced the Coils and Wires (this is more prevalent on the 99 & 00 models). The problem still exists but doesn't seem to be as bad at higher RPM. I replaced the spark plugs before the smog check and verified them when replacing the coils. They looked fine. Today I checked the Crankshaft sensor gap. One of the nodules was a little tight at .020 and I adjust the gap to be .025. The problem is still there.

I've disconnected the Link ECU and ran jumpers across the wires to the coils. The car drives like brand new. Flyin Miata sent me another ECU to try. I hooked it up and the problem came back.

A little while ago, I hooked up my datalogger to the power lead that comes to the Link ECU. For the most part, the voltage was from 12.8 to 14.8. There are a few dips at 11.2 to 11.5 and spikes at 15.5 to 16. I need to run more tests to see if the dips correspond to when the sputtering occurred. (Its my first datalogger)

Any ideas?

 

I had this exact event happen on my car and after talking to FM, this is what I did: Check your AIT readings. If it sticks at a steady 100* (C) no matter what, you have a problem, so check the actual AIT sensor. Mine had gotten corrosion on the contacts, presumably from the WI, even though the nozzle is post-AIT. FM said that sometimes the solder joints can come undone, or the wire is too brittle and messes up, so those are some other options for problems. Anyway, I cleaned my sensor and was boost happy again.

 

Thanks for a quick reply. I did check the AIT sensor and connections. It looked good. I checked for resistance on the sensor itself and its at 1.55k. From the repair manual the range is from 76ohms to 4k.

I used the datalogger to check the air temp (see attached)

BTW, what is the WI?

 

Interesting. Your problem sounded the same, but I guess it is not. Sorry, I can't help past that.
WI = Water Injection

 

Thanks for responding. At this point I'll take any suggestions you may have.

 

I'll post a quote when I asked about my problem:

 

Well Luckwow the spammer was taken care of but now I'm left with this goofy looking post now that his post has been deleted. Feels a little like the dreams where you suddenly realize you are naked in public with his post deleted and mine still sitting here.