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I have a 92 mx-3 just did a engine swap 1 month ago 4cyl , anyways it's studdering after it warms up ,like it has not enough fuel going to injectors, i have changed fuel filter (didn't help) tried new cap and rotor (didn't work) plugs are new, and just passed emmisions so it's not the cat and wondering what the f#&* is wrong with this piece of crap i have a good guess that it might be an injector but don't know any suggestion would be a good one! thx R.C.

what swap and has it been doing it since the swap?

Make sure there are no hairline cracks in the large ribbed rubber air intake hose. If it's not the prob, at least you'll rule it out & only takes a few minutes to remove the hose and flex it while inspecting. Sometimes very tiny cracks develop between the ribs which then will allow extra unmetered air into the intake stream. If you find cracking, a tight wrap of duct tape will give a temporary fix until the hose is replaced.

This problem can mimic poor fuel flow because that extra unmetered air isn't offset by additional fuel since the VAF/MAF can't measure the leaking air coming into the intake air stream. While the engine is running from a cold startup, the fuel mixture is extra rich and idle speed is higher so you wouldn't necessarily notice a problem in this scenario until the fuel mixture leans out for normal operation - like the problem you are describing...

does it do it at all RPM ranges? could be your TPS.

wat about when udrive if so maybe fuel pump but like neutral said check for hairline cracks in the intake hoses and vac lines.

thanx for your imput guys but i fixed problem who would have thought a freakin plug could cause so must b.s. oh well i just had to tighten the end so it would fit on the plug better well at least there is some info if it ever happens to anybody else . . . right thx guys

so what swap did you do?