Hme2017

Hello Everyone,

so a little background on my truck: I got a new to me 93 s10 blazer 2wd 4 door with a 4.3L vortec V6 VIN W from a friend last year. I was told the engine had been budget rebuilt about 4 years ago and should be in decent shape. It was parked due to the brakes going out. I loved the body style, and the body and frame are in pretty good shape so for a couple hundred bucks it was hard to say no! It barely ran when i got it so my initial plan was just to get running somewhat reliably by replacing only the necessary parts, rebuild the brakes, and leave it at that. The more I looked at it though, the more I really wanted to make it a daily driver! I've done small block chevy top end rebuilds on 305s and 350s, but am by no means an expert.

I pulled the engine and trans due to leaks coming from basically every seal you can imagine (timing cover, oil pan, oil cooler, all lines to radiator for trans and oil, PS pump and steering gear, AC compressor, rear main, trans input shaft, output, speedometer sensor housing, rear diff), noticed the suspension was in bad shape, and went overboard. I rebuilt the rear end, front and rear suspension, the entire brake system, replaced the PS pump and gear, removed the 4wABS block that was dead, resealed all leaks on the trans, replaced the fuel pump and filter, and finally got around to getting the engine. Before the top end rebuild, the engine ran okay at higher rpms, but idled very rough. It also had a hard time starting and would stall out frequently. On my way down, found that the spider injector was pretty much dead as well as a small coolant leak from the lower intake gaskets into 2 cylinders causing some white smoke at startup. I assumed these two problems were the main culprits in the stalling issues. The head gaskets, valves, and cylinders were in good shape so i was hopeful it could be brought back to life.

With all that done, I put it all back together and started it up. To my surprise, it started up first try with no issues! After getting the ignition timing set, it seemed like it was idling great after the rebuild, but as it warmed up, I noticed it started to slowly develop some roughness and shaking. When I pull the throttle, there is about a 1 second delay before the engine sluggishly revs up. Test drove it, and there was just no power to speak of. At WOT, I can barely get out of 2nd gear on a straightaway, and going up hill is even worse. When returning to a stop however, the engine runs a little rough, but doesn't act like its going to stall.

Here is where I'm hoping someone can point me in the right direction. I first checked all plugs and wires as the easiest troubleshooting option, with everything working as expected. Since the spider injector, fuel nut lines, pump, and filter were all new, I thought I'd save that for last. Next, I thought I'd look for vacuum issues. I had to rebuild the vacuum lines using the FSM diagrams due to the old ones having rotted away to dust. This blazer has the vacuum ball on the passenger side and the vacuum controlled ac vents and cruise control. I pulled my new lines from the back of the manifold and plugged the port to eliminate a leak in the new lines. Nothing. Next, checked the brake booster, but still no change. I kept hearing a slight hiss in the engine bay which is why I initially thought a vacuum leak, and finally found it to be coming from the line running from the PCV valves to the upper intake right beside the MAF sensor ( I assume this is the routing, at least this is how it was when I got it). I pulled the line and all of a sudden the RPMs jumped up to i guess around 1500 or 2000 (don't have a tach). If is replaced the line or covered the port, the engine nearly stalls out and settles down to around 600 rpm and rough. I decided to see if leaving the line off would do anything for my power issues. I pulled the throttle and the response was nearly instant. I got in the truck and shifted into reverse. The shift was much more violent, but letting off the gas, the truck starting moving quickly out of the driveway. Got on the road, and had plenty of power. The only issue now is that there is too much power. Shifting between gears is fairly rough, and when shifting from park to reverse or drive the whole vehicle violently lurches even making the tires chirp!

I don't know really where to go from this point. I was reading either the TPS or IAC sensors could be to blame, but not sure. Not sure if it helps to know, but if I unplug the MAF sensor, the truck dies. Unplugging the TPS sensor, causes the idle to surge until I plug it back in so these sensors are doing something. When I unplug the IAC sensor however, nothing seems to happen. The idle doesn't change at all. I thought before I start shotgunning sensors at the issue, maybe someone might know based on my symptoms what could be causing this, it may not even be sensor related.

Hme2017

Port that had the PCV valve line connected

Disconnecting this line drastically increases power, but causes high RPM and a lot of vacuum noise