Rough running 95 Blazer
Ok, I've searched here, and over on Chevy Talk, trying to get some ideas on where to look for possible causes. I'm just going to cross post to here as well, since there seems to be more S-10 owners with the 4.3 V6 here. This might be long, but I'd rather have more info out to you than not enough.
Ok, A friend of mine has a 95 S-10 blazer with CPS injection. After we replaced the head gaskets, it's developed a rough idel/run/miss condition. We've already replaced the distributor,cap, rotor,wires and plugs, along with a fuel filter trying to get rid the rough run/miss. We've even cleaned out the EGR, as it was clogged, and replaced a couple of sensors, as gas mileage had dropped to terrible. It runs even worse when it gets wet, but runs good on the highway with your foot into it. The ses light comes on when it feels like it, and sometimes even flashes. I don't have a code reader (I only own 1 OBD2 vehicle, and haven't needed it), but we are looking at borrowing one to see what codes it'll throw. Also, I don't have a fuel pressure gauge. It does blow black smoke on fire up, and seems to run better when cold than warmed up.
I'm beginning to think either the fuel pressure regulator, the lines under the cover, or possibly a clogged map sensor.Any ideas that we could check? We're looking at pulling it in over the up coming weekend, and see if we can figure out what's wrong.
Ok, a little more info. The truck was taken to Autozone to get the codes read. It coughed up, multiple miss fires. Well, we knew that already just by driving it. Anyway, another friend suggested a coil swap, or the module that resides next to the coil being a possible culprit. We're looking at what could make it run like crap, and what could make it even worse after it gets wet (like after a car wash). We're still not sure on the spider/regulator, as it runs good as long as you keep your foot in it, and that wouldn't / shouldn't make it worse when wet.
We replaced the front O2 sensor, but haven't done the rear yet. The codes weren't printed out at the zone, so I don't know what the actual numbers are. Head gaskets were replaced about 5 months ago, due to the gasket blowing thru at the very rear of #5 cylinder just above the locating dowel pin (standard place they go, even on V8's). We used Felpro head gaskets, intake manifold gaskets, and the plenum gasket. Distributor was pulled, and the new one was indexed and dropped right back in place. A new module was put in while we were there as well. It has a roll pin to locate it to the manifold, so it's gotta be pretty close, and you can't fine tune them for a tooth being off. The TPS was replaced, and the MAF was cleaned with electrical cleaner, and re-installed. We do have a spare of both though, as we're still hunting down the problem, and nothing has been thrown away. The plugs looked real good (Bosch platinums, but were replaced with Rapid Fires),with a nice clean burn. That's what's throwing me off. He told me that removing the vac hose to the vac ball on the hood made it run a little smoother, until the computer caught up. We're both thinking is an electrical issue, due to it running worse when it gets wet. I mean a FPR or a nut kit won't change if the outside were wet, but this thing runs terrible after a car wash. Can the ECM go bad intermittantly? We do have a line on one, IF needed. Thanks for any help or ideas, as we're grasping at straws.
Also, I'd like to thank gchemist for his help over on Chevy talk, as he's tried to give me some ideas. Thanks again for any help.