Ok, I recently purchased a 1989 blazer with the 4.3 motor TBI for $75 in pieces. put it all together, and it's in great shape, no rust, new mufler, etc... (former owner was a mechanic who was about to finish restoring it, but was involves in an accident and died :S )
My problem is the motor is running like crap...
When you first start it it runs really rough and will not come close to idling without help using the gas pedal... It misses a lot and shakes like there's no tommorow. once it's been warmed up a bit it will idle, but roughly with the rpms going up and down and will stall after 10-20 seconds if not given gas. If I go for a short drive (I don't have it registered just yet so no long drives) it will not operate between 1/8 throtle and full throtle... if you just barely touch the gas pedal, it will slowly accelerate. If you floor it, it will hesitate for 1-2 seconds, then accelerate like it should. however, anything in between and there's no power. If you floor it a few times, this "dead" zone will be a little less noticible, though still there... Also after flooring it when you come to a stop it will for the most part idle just fine (even in gear), though there's a soft "poof" ever second or two, with the engline giving a soft shake when it happens. The check engine light does not come on at all... If I let the engine cool down, the problem gets worse again.
Here's what I've tried doing to fix it...
1) checked all the spark plugs... all were the same color, almost white with a bit of a tan.
2) tested all the spark plug wires resistance, all were under the 30,000 ohms limit stated in my manual
3) with the engine running, and IAC valve disconnected (as it said in the manual) disconnected one at a time each spark plug wire and listened for a rpm drop... heard a small drop in rpm on all cilynders (and shocked myself 5-6 times :P )
4) cleaned IAC vavle
5) cleaned and sealed with high temp silicone the EGR valve
6) checked the PCV (or PVC, can't remember what it's called, the one on the valve covers) valve, works fine
7)played with the timing, no effect one way or the other...
8)checked injectors, both giving a good spray (at idle anyway)
Also, I have a vent hose which I cannot figure out where it goes... it is on the right side of the engine (left if you're looking from the front of the truck) on the intake manifold in between the throtle body and the valve cover, see
http://www.clubplus.net/~tommy/blazer/TBI.JPG for a picture... (not my pic, found on web) When this vent house is left open, the motor idles high and shakes a LOT, when plugged, idle is low but engine doesn't shake near as much. I've looked all around within reach of the hose (which is about a foot and a half long) and can't find anywhere where it could go...
I should also point out that this engine sat for 3-4 years... not sure if it effects anything...
Anyone have any ideas? I really need to get this truck running as my current car is heading for the scrap heap soon... Also, my friend can get me a carburator for the engine to replace the TBI setup for $120 CND, would this solve the problem? and would it be worth it?
Thanks a bunch, Thomas