The code sheet is in the car, but If I remember correctly, its a PO300. Random misfire, I was told that it could be the optispark, the coil, or excessively high or low fuel pressure.

LT1 6 speed, stock, except the air filter.

I have new plugs, original equipment AC, nothing fancy, and new wires. I was very meticulous about running the wires, nothing is touching or burnt through.

Its been "kicking" lately, like if you accelerate, it wants to lurch a few times as it speeds up. Idles rough too. The worst is at 55 in 5th gear, floor it, and its really rough, will accelerate, but kicks quite hard in rapid succession.

Where should I begin? I dont have a lot of money to throw at this problem.

Thanks in advance.

 

(All information im going to give comes from the knowledge i learned about my 4.3 v6 on my 97 blazer--found that the most common ailments are spread through a range of motors)

you said its kicking while accelerating, that tells me it could be the fuel is having a hard time getting through either the filter or the injectors.

My blazer did the same thing, kicked/bucked while accelerating at over 55mph, changed the filter and used a bottle of Injector Sting, it ran smoother. Im not sure if yours has injectors but if it does one or more might be clogged, have you ran any kind of injector cleaner or any gas treatments through it? Have you changed the fuel filter at all before/after this began happening?

Since you don't have a lot of money, if I was you id start by putting a bottle of injector cleaner in it, I prefer the Injector Sting only 7 dollarts at your local autozone, might get lucky and they have a BOGO sale going on for it. Rough idle.. hmm thinking maybe MAF sensor (if it has it..)

The p0300 is most commonly found on the secondary side of the ignition.. plugs, coils, caps, rotors, etc. Hmm if you have a egr valve, trying cleaning it... that might help smooth out the rough idle along with the maf sensor. Im not sure about LT1's but the things I listed to do are pretty common and simple things. When you changed your plugs, did you make sure they were gapped properly? Have you checked the gap on them lately?

Have you done a compression test yet to find out which cylinders are misfiring at what points? Have you tested your coils to make sure they are getting the right voltage to them? You could just have a dead coil and the other coils (assuming you have coil packs instead of a distributor) are working twice as hard to pick up the slack.

 

New fuel filter. bought injector cleaner, STP a few minutes AFTER the check engine light came on.



The MAF sensor threw a code a couple weeks ago, I got some MAF cleaner, and the code did not return. The previous owner had run it without the air cleaner attached, I dont know for how long. It was just rolling around in the little bay.

Where is the EGR valve?

It has a single coil that goes to the optispark. Dont know how to check those components.

Dont know how to check compression.

 

Most times random misfire is due to a lean fuel mixture. May want to replace the fuel filter, and if problem persists check the fuel pressure with a gauge.

 

Fuel filter is new, under 2,000 miles.

 

Nice looking car though, sorry, had to show it off a little.

 

The opti spark is notorious for issues so I'm thinking that's the problem, is your water pump leaking on to it?

 

egr is at the back of the intake manifold. check fuel pressure like pete is sayin. did you happen to dump the old filter out to see how dirty it was? do you know how old the opti aka distributor is. change the pcv valve too. also may have done a poor or improper clean job on the maf, they are easy to screw up. heres a site with some great stuff on it. lots of info. 4th Gen LT1 F-Body Tech Aids

 

FWIW, I chased a PO300 code, with badly shaking engine, on a car two different times. Both times it turned out to be a clogged fuel injector. And that made sense, since if one injector is making a cylinder run lean, that whole bank is going to register lean by the oxy sensor. You get a random misfire because the system doesn't know which cylinder is the lean one. Also, I tried Lucas fuel injector cleaner for a couple tankfuls first, and that didn't help at all (insert commercial plug here). I was able to figure out which one was the culprit (did the pull one spark plug wire at a time trick), then I pulled out the injector and soaked it in carb cleaner. Ran as good as new after that.

 

I can't afford 700$+ for injectors, thats if I put them in myself. Is there a rebuild kit for them?