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I am having some weird problems with my vehicle within the last couple of days, hopefully you folks can offer some input.

First of all when i start the car the idle is jumping up and down between 500-1500rpms, then sometimes it drops right down to 500 or so rpms and the car cuts out. This strange behaviour also happens in traffic sometimes, idle jumps up and down and vehicle dies and I have to restart.

The other problem I am having is the vehicle will sometime stumble or bucking sharply under acceleration, this happens for a short while then the vehicle accelarates as normal.

The only thing I have checked so far is spark plugs and wires and these are fine. I even switch to some other plugs and wires for a day or so and still am having the same problem. The connections for the intercooler seems to be okay as well.

The vehicle is a turbocharged 94 Mazda MX3 1.6 DOHC with TurboXS BOV, 1.8 Miata Injectors, Walbro 255 fuel pump, Cartech RRFPR and FMIC. The engine is completely stock using a GTX Manifold and VJ-11 turbo.

Please help. Any suggestions would be appreciated.

check to see if it has any CEL codes in it

i'm thinking the TPS

or perhaps it could be a vacum leak somewhere.

I second the leak idea, but I would target the piping and BOV connections.

Thirding the vaccum leak idea, is your bov staying closed at idle?

Sounds to me like a simple fuel delivery problem
check filter and pump or clogged lines

got a fuel pressure gauge ?? what pressure you are running on idle and at full boost (btw what boost you're running?)..myabe your 2025 isn't rising the fuel properly..what you a/f ratio is?..maybe you need to play with the rising rate on your fmu..but that's only a guess since we don't know much about your car..this is for the bugging problem

as far as the rpm goes, I would think a bad tps or it isn't asjusted properly? vacuum leak is not a bad idea too

Accidental double post..

<small>[ October 21, 2004, 10:56 PM: Message edited by: mx3man83 ]</small>

I had a similar problem on my NA klze. Turns out it was the TPS and CTS. Not too familiar with the 4 cylinders, but its something to look into.