Random/Multiple Cylinder Misfire

2000 (or so) Cavalier 2.2 has 25k miles on it. Driven maybe 10 miles per week. Ran fine about 10 days ago. Sounded and felt like a vacuum leak but after checking things out now am leaning towards clogged injectors. AZ is tough on gas and since it sits most of the time...Code was simply P0300, which just tells me it's running like crap. i put a bottle of injector cleaner in it, still no help. When I pulled the plugs # 2,3 and 4 looked rich and #1 looked really lean. Backfires at around 3k rpm and shuts down. Any ideas would be appreciated. I havn't wrenched on injection before, how would I check to see if #1 is clogged???


Thanks in advance...

change the fuel filter first

change the fuel filter first

Where is the fuel filter located on this particular car?

Also, How do you explain only #1 so lean?

Thanks,

Could be an injector problem, could be something else. The best way to check an injector is (well, the easiest way anyhow) - while the engine is running, pull off each injector wiring connector one at a time. If you take one off and the engine does not bog down, that cylinder is the culprit.

The fuel filter should be underneath the car just before the fuel tank probably on the right side (not sure for 2000). But also check no vaccuum leaks, fresh gas, air filter box isn't full of mice nest, etc. I would be tempted to fix the random misfire first, then worry about an individual cylinder.

Could be an injector problem, could be something else. The best way to check an injector is (well, the easiest way anyhow) - while the engine is running, pull off each injector wiring connector one at a time. If you take one off and the engine does not bog down, that cylinder is the culprit.

The fuel filter should be underneath the car just before the fuel tank probably on the right side (not sure for 2000). But also check no vaccuum leaks, fresh gas, air filter box isn't full of mice nest, etc. I would be tempted to fix the random misfire first, then worry about an individual cylinder.

Thanks for the help. I did check for obvious vacuum leaks, I veared from that because of the sudden nature that this happened. I took the top end apart, well, just the covers so the fuel log is exposed and I'll check the filter tomorrow. I'll try your test tomorrow as well ans see what happens. I can't tell if it's a 2000 by the vin but I guess I could look it up, should be the same from '99 to '03. How do I pull the injector if it does become the culprit. I can't find the misfire, if I could it would run good. I looked in the filter case and all is clean. I added techron to '91 oct. to the tank and ran it and nothing. Had some oil in the 2,3 and 4 spark plug threads and again some on the air intake flange, which is leading me right back to where I started; injector clogged. Any input would be appreciated...

Thanks

Try changing your coil packs ( 2 of them) Sounds similar problem liek what I had and I changed them now im running fine. I just went ahead and changed both of them since one was gettign changed might as well do both knwo what m sayin. I got to it with a swivel and some extensions and a wratchit and i was under the bottome of the car.. Good luck with it....