Engine Missfire

[Tommy_Boy]

Very recently I had all my belts replaced including the timing belt... The day I got my car back it starting making a wierd sound when I shut it off as if it were blowing air back out the RAM air... I didnt think much about it and thought I just hadn't noticed before so I installed headers and started getting the P0421 code... I used your guys' help to fix that! And Thank you, but now I was driving along the freeway and my car just ran dead out of power and started dropping in speed but held the same RPM and it sounded like crap, on top off all that it smelled horrible!! I down shifted to 4th and nothing rpms stayed the same and i still lost speed so i down shifted again and the car like sputtered and then took off and ran normal for the rest of the 13 miles home... Now i have the Code p0300 and the p0421... Any Suggestions?

[Kansei]

That smell.. was the smell of your cats melting :(

If it's a multiple cylinder misfire, it could be a coil pack gone dead. Otherwise I'd check your spark plug wires and replace them.. How many miles do you have on your current wires/plugs/coils?

[thrasher]

Mine did the same thing. Restarted and it was fine for a while. But then unexpectedly it would do it again, a sudden loss of power and egg smell.

It was a coilpack for me. Easy to fix.

[bazooka joe]

o2 sensor??

[Tommy_Boy]

by coil pack do you mean the 2 individual ignition coils?

[Kansei]

by coil pack do you mean the 2 individual ignition coils?

yup. I'm trying to find a good place to buy them, the napa web site had them for 17.99 a piece but I ordered them and got an e-mail back saying they were no longer available :(

[Tommy_Boy]

Thats pretty crappy... I'll let you know if I find some because I am way too nervous to drive my car untill I fix that shizz nit

[GNO]

There are a number of causes of random misfires that would trigger the p0300 code:
coils
wires
spark plugs
injectors
fuel pump
fuel pressure regulator
primary o2 sensor
catalitic convertor

Start with the easy stuff by testing rathan than just throwing parts at it until it works.

This is the order I'd try:
Inspect the wires and plugs.
Check your exhaust flow to see if the cat's plugged up. Have someone rev the engine while standing near the back, flow pressure should increase with RPM.
Plug in an OBDII scanner and monitor individual cylinders and O2 voltage. If the O2 voltage goes wacky before the issue arises, then that may be the culprit. If it misfires before an O2 voltage spike, then the O2 sensor is working properly. If you can narrow it down to a specific cylinder, then either the plug, wire, or injector is bad. If you isolate two cylinders and that happen to be on the same coil, it's probably that coil.
Test the coils with a spark plug test light.
For the pump and regulator, hook up the fuel line to a pressure gauge. Fuel pressure should remain steady and increase as RPM increases.

The sulfer smell indicates a cat issue. The unspent fuel burning in the cat is causing that smell. If the cat isn't bad, it will be soon. Don't replace it until the issue is resolved. Otherwise, the new one will meet a premature death. If it runs fine with the exhaust disconnected, the cat was causing the problem.

[Dave_x]

I had a similar problem. I'd get P0300 codes and a drop in power for a few seconds. Every once in a while I'd get the P0421 too. I couldn't find coil packs anywhere for under $85. I ended up doing the 2.0 to 1.8 coil swap (http://www.msprotege.com/forum/showthread.php?t=123650373). The mod took care of the P0300 and I think it runs a lot smoother.

I'm still getting the P0421 though. Not sure if I should take it in to the dealer or just do the CEL Eliminator (http://www.msprotege.com/forum/showthread.php?t=52498\). Even though emissions have an 8 year/80K warranty, wouldn't they bounce me out because of the coil pack swap?

[bazooka joe]

yup. I'm trying to find a good place to buy them, the napa web site had them for 17.99 a piece but I ordered them and got an e-mail back saying they were no longer available :(

i've got a set for you when you show up next week!! :)