now what..?

[homE30grown]

so far you guys have been very helpful and pretty accurate with the problem solving, so here i am again seeking more help!

well, my previous problem was the AFM (car would idle fine but stumble and jerk in low rpm's upon acceleration) so i purchased a new AFM about two months ago. it ran fine for a couple days then the problems came back so i bought a new fuel pump and my car has ran very good with no problems up until a week ago.

i was going about 15-20 mph and the jerkyness came back (symptoms from a bad AFM). i parked it for about 30 minutes, then it ran fine for the next 3 days. then one night it started doing that b.s. again after i warmed it up and drove off, so i let it sit overnight and it worked fine the next day.

two days ago it happened again so i opened the hood to check it out while it was idling. pulled the throttle a little and a popping noise started coming from the airbox as i gave it gas (doesnt get above 3000 rpms). the next day i tried starting it and all it would do was crank with the popping noise coming from somewhere. i was told it could be a bad catalytic converter so i cut before it and tried to start it. the engine would turn but not start, then after a minute or so, it started for a few seconds and died out and hasnt started since. i still hear that popping noise when i crank it, even with the cat converter disconnected. what the hell is going on here?

whats new on the car: afm, fuel pump, filters, cap, rotor, wires, plug, coil, and brand new bosch battery.

-matt

[bddog]

Could be a bad cat. Happened to me once on a vehicle. It is like putting a potato in the tailpipe. No exhaust=no intake

[bddog]

usualy they rattle when they are bad

[jlevie]

A popping sound from the airbox probably means that the car is backfiring. That could be from an excessively lean mixture (AFM, fuel problem, or massive intake leak), improper spark timing, or intake valve problems. The first thing to do would be to verify that spark timing is correct, that there's not a large intake leak, and that fuel rail pressure is within spec. After that a compression & leakdown test will tell if there are valve problems.

[euroshark]

That could be from an excessively lean mixture

It sounds like an intermittent fuel pump to me... Since you replaced it, I wouldn't suspect that, but I would suspect your fuel pump relay, fuse, or the physical wiring! Try jumping the relay with a small piece of wire, start the car, and if the problem goes away then you have a bad relay. I'll help with instructions if you need them!

You could also check your fuel pressure regulator... though I'm not sure how without using a gauge. I have a spare 2.5 bar FPR I'll send you for like $10 shipped if you want.