2000 Buick LeSabre. After replacing starter. The car died and had to be jumped. Once the car had enough power it started but now the car runs rough it vibrates alot on idle the rpms are alot higher then they should and they fluxuate often. the service engine light is flashing and I get error codes po300 and po300 P. I replaced half of the 6 spark plugs and connectors (rest are in back of engine and hard to get to) as I though that might help but i don’t notice a difference. The exaust has a weird rotten smell and I smell a sweet smell when turn the car on. Also the instrument panel mades a short grinding when the needles are moving after turning key anyway in the ignition.
And that start exactly after all this had happening.
My guess is bad fuel pump or catalytic converter but there are many things that can can multiple engine misfire. Any info you may provide would be greatly appreciated. -jadon
[moved to M/R topic -lackeyjr]
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Let me see if I got this scenario right.
You disconnected the battery, replaced the starter, reconnected the battery, and that’s when all the problems began?
There might be a problem with the side mount battery terminals.
The GM side mount battery terminals are notorious for hidden corrosion which can cause a voltage drop to computers/modules.
Given the age of your vehicle, I’d replace the battery cables.
Tester
Battery cables as @tester said. Where is the sweet smell coming from? That is usually a antifreeze leak.
The exhaust odor might be the effect of raw fuel (due to the misfires) going through the cat and out the muffler. My guess goes along with the posts above, if it was running fine before, then your replaced the starter b/c of a no-crank problem, you got some kind of battery, electrical, or ignition system problem. Ask your shop to measure the battery voltage with the engine (sort of ) running, both at the battery posts, and at some point beyond the battery posts. At the battery posts it should read 13.5 volts - 16 volts, somewhere in that range, engine running. And it should be very close to that at points beyond the battery posts.
There’s a big thick wire that goes from the battery positive directly to the starter. If that wire was shorting on something, this could happen. That’s probably what I’d look for first if I had that problem, crawl under the car and inspect where that wire connects to the starter motor, make sure it isn’t touching anything it shouldn’t there.