vbb

J-Rod... that's weird that your car is doing this but you're only getting the CEL for an aftermarket cat. It turned out that my car was running waaaaaay too rich due to some aftermarket injectors that the prior owner neglected to tell me he left on the car. That was causing misfires, a sloppy idle, causing me to dump fuel, killed my catalytic converter, the works.

Absent any codes, it's really odd that your car is still having the problems.

hustle_kaing

VBB, sorry for the noob question, but what does the car do (feel like) when its misfiring, can there be small misfires and big (bad) misfires? or they all feel/sound the same?

vbb

There's a possibility that your car could misfire and you not be able to feel it... but a misfire generally feels like a hesitation or bogging when you're under acceleration. Misfiring is bad. If you suspect your car is misfiring, try not to drive it (and if you have a blinking CEL, definitely don't drive it) and get your codes scanned at a shop or Autozone.

hustle_kaing

Ok, well the CEL is not on, but I have like a small idle vibration/sputter problem. It only happens at idle, the whole car shakes, not a lot but not little either, but only for like 1/2 a second then goes away for like 5-10 seconds then it does it again, happens mostly when the car is cold, meaning throughout the first 10 minutes of driving the car in the morning going to work and then from work to home. After the car is fully warmed up (after 20+ minutes of driving )it rarely does it. The car has new spark plugs, cleaned IAC valve, cleaned MAP sensor and cleaned the PCV valve and now it also has a micro filter/oil catch can, I've also adjusted the throttle body cable (you can see my post earlier in the thread ^^^). The vibration/shaking did go away completely for 1 day after I cleaned the IAC valve, but then it returned the day after. I havent given it much importance anymore since it doesnt give me a CEL.

hustle_kaing

I also noticed the small sputter on the exhaust, if I put my hand in front of the exhaust tip I can feel the smooth push of air at idle, then the small surge (POOF) against my hand.

vbb

What you're describing does not sound like a misfire to me, which would be a good thing. But I don't know what could be causing that, given no CEL and you've cleaned the MAP, IAC, and changed the plugs. Does it drive fine when you are on the gas?

Kirpich

Well, when all else fails, ppl usually go for a new set of injectors. Try swapping a set out with a buddy. Make sure he/she has the same chassis (AP1 or AP2). Don't switch them around, as AP1 has 330 cc/min injectors, AP2 has 360 cc/min. If you use different ones, the ECU won't know it, and with the same pulse the engine will be receiving a wrong amount of fuel, negating the entire test.

So, if you have AP1, use AP1 injectors for a swap.

vbb

Umm, what? I'm pretty positive the injectors are the same from MY00-05.

But yes, I agree... if you've done everything else, it could be an injector issue. I know that ended up being the problem with mine.

Kirpich

No, they're not. The F20C that AP1s use has a smaller cylinder. do the math, 1998/4, roughly 499 cc per cyl, AP2 have F22C, therefore 2199/4=549cc or so per cylinder. That's why AP2's injectors will squirt more fuel out per same width of injector pulse, in other words, more fuel delivered at same injector duty.

vbb

I understand your math... but on multiple websites and parts list, they have the same part number.