BlackBird97

I've had this damn PO300 "mutliple engine missfire" for the last 2 or 3 months. I've replaced the opti, and the opti harness. New plugs, and new wires. I can't figure out for the damn of me where it is comming from! I currently have the hotcam in my car, i know it does create a slight miss, but I got the car re-tuned twice. So according to SpeedInc it shouldn't be there and yes I've brought it back to them numorouse times.I'm just gettin tired of waitin weeks at a time gettin my car back. Emissions testing is comming up. So does anybody have any quick fixes or suggestions? I am at a totall loss. I know one of my buddies said there is a certain code I can put into the computer via Tec 2 to clear it out permanently, but the only problem with that is, I don't know if its somthing seriouse or not. Thanks gentlemen.

-GTP Stage 2 Heads
-Hot Cam setup 1.6
-Full exhaust
-Long Tubes
-Cutout
-O2 trip sensors
-MSD 6al
-Everybolton
-Walbro 255
-Race tronix 32lbs
- Holley AFPR

Just a list of stuff that may have an effect on answers. If you need anymore information just post, and i'll reply promptly!

Zeueses 97 RamAir

try your wires see if there is a short by the headers being so close. also try the cps i have a new one im the box if you want to buy it dont need it, i had a short in the wires

BlackBird97

CPS? What's that?

moparman

CPS = Crankshaft Position Sensor

The good ol' PO300. It seems to be a different cause for everyone who has had it. Most don't post back what caused theirs. I chased it for a couple of months, before the scan tool finally pinpointed the cylinder the miss was in. It turned out to be a bad plug wire that looked perfectly fine, until I took it off, then I could see the fine black line by the sparkplug boot.

Do you actually have a miss, or is the car just giving the code?

BlackBird97

It says it's missing, I can feel the stutter of the car missing at some points. So I am guessing it's missing. Or hoping it's missing...so then I know it's somthing that can be fixed haha.

CamaroRob97

Like mentioned before have you checked your fuel pressure at all? with the vehicle running hook a gauge up to the fuel rail (with the shradder valve removed) and pun it through a nice wide RPM range. Also you say it feels as though is missing, and your sure the plug wires are good, i know its a PITA but check all the other to make sure non are carboned up, also if they are good we know u got spark, put a noid light on each injector to make sure they're each firing...can't seeing it being you ignition module....cam position sensor??
just my $.02

hope this helps

Rob

BlackBird97

Arrite, I've been doing alot of research on the Crank Position Sensor, I found that its about 70 bucks from GM. I couln't find the Cam Position Sensor, checked Chiltons, engine diagrams and whatnot. Does the 97 LT1 Have one of these ? All I could find was the Crank Position Sensor. Looks like an easy install.

CamaroRob97

Well in all honesty its been bout 2.5 years since i've even really touched an LT1 let alone an f-body, so yeah my Cam posi. sensor info may be off. But as far as the CPS Yes its at the bottom of the timing cover...can't remember if its d/s or p/s...(Man i need to get to the desert so i can my off the 'clipse an get another f-body )

Dave89IROC

CPS is on the pass side of the timing cover, at the bottom

LT1 don't have a seperate cam sensor, all it needs one for is fuel/spark synch, so the high and low res pulses for the opti suffice, and all it uses the crank sensor for is misfire detection

BlackBird97

Hmm I see, well tomorrow I'm goin under the car, checkin for burnt wires, and investigating the CPS. Are those things prone to go out after a while? And Rob, it's arrite man, there will be an F-body there for ya when ya want one! We'll all still be here!

madwolf

On OBD2s (particularly LT1), P0300 can show up after installing a cam that is more radical than stock. If it does, there is not much you can do about it since the system was designed for checking misfire on a stock cam. Having said that, I'm almost 100% sure a new sensor won't solve your issue. Your best bet, in my opinion is to have the code disabled. You should be able to pass with 2 "NOT READY" flags and this would only trigger one.

BlackBird97

Yeah figured out it isn't the CPS....I am leaning twords the wires. But if it's not that. May god help me!

madwolf

If you don't want to continue doing work in vain and replacing things without any results, read my above message.

Z95m6

lol.