Hi guys, I recently got my 2002 Grand Prix back on the road after a little over a year of sitting in a driveway. It's been running for the most part, but a lot of rust and general wear and tear have pulled me down the road of self service auto work, since most shops want to charge as much as the car is worth for the problems it has.
I recently did an intake gasket replacement, and I want to say it went fairly well, although it revealed a broken upper intake manifold during the process. So I replaced upper/lower intake gaskets, EGR gasket, etc (everything that comes in the Dorman gasket set), and pulled an upper intake manifold off of another 2002 SE at a junkyard. I hooked everything back up**, refilled/changed coolant and oil, and started it up. The car idled like crap compared to a few days prior, but once it got going it drove smooth as butter. Still, it idled terribly at stop lights and whenever I started it up. Now, today (the day after I first turned the car on after the gasket change), I was under the hood looking for a vacuum leak, and discovered that I had NOT hooked everything back up, but rather forgot to connect one tiny little hose to my upper intake manifold over by the alternator. I dunno what it does (it snakes around the coolant reservoir under the fuse box and disappears into whatever is down there), but as soon as I plugged that back in, the rough idling decreased drastically.
Still, my "Service Engine Soon" light is on, and it wasn't as smooth as it was a week ago, so I went to Advanced Auto and got them to do a diagnostic with a code scanner thing. 6 codes dropped. C0245 (ABS wheel speed sensor), P0171 (Bank #1 too lean), and P0300 (random multiple misfire detected). P0171 dropped a 2nd time, also for Bank 1, and P0300 came twice in a row at the end, so really only 3 codes came through.
Now, I'm not too worried about the ABS one, but I'm still a little curious as to what I need to add to the laundry list of parts for this thing should I ever get to fixing it down the line. Especially if its something I can just buy off of rockauto and install myself. But the other two are the important ones... I don't know if it's an important detail, but I *'d the "hooked everything back up" bit because I forgot that tiny hose, and wonder if maybe that caused one of the P0171 codes? Or if it could have had any impact whatsoever on the current situation? I plan to get a can of that carburator cleaner stuff and seeing what I find (I suspect my upper intake gaskets, since they didn't seem to seat properly when I got to installing them, but they look ok now that everything is bolted down), but I have no idea what to do beyond that. Is there a way to check my coil pack/wiring to make sure that's all ok? I noticed one of the plugs (I think for spark plug #6, but I'm not 100% sure) was loose on the coil pack when I found the unplugged tiny hose to my UIM.. I've reconnected it, but that was before going to AA for the code read. Could that have been a cause for a code to drop?
For what it's worth, this car is the first car I've gotten my hands dirty with. Aside from helping my dad on the occasional oil/brake pad change, my experience with cars can all be boiled down to the last 3 months when I finally changed out the starter on this GP to get it moving again. My tools and resources are limited, so taking it to a mechanic is pretty much a no go unless the service in question is free. I don't have a big budget to spend on things just to test issues, so if there's anything I can test with just my senses and some socket wrenches, that'd be great lol. College budgets don't allow much wiggle room for going crazy on testing kits... Thanks in advance for any help! I can provide pictures or video of anything that needs picture/video if necessary to help solve these issues.
