Alright searched all over the web can't find any help so here we go.

My problem with my 97blazer 4x4 is when I'm going down the road I'll be getting good mpgs then suddenly it will drop to 10ish and my blazer will start to run like crap, and I'll get a slight jerk when I let off the gas pedal. It will idle like it should with an occasional rough idle, but if I rev it up it will idle down fine. Now when I'm going down the road and it starts to act up I'll pull over and hook up my code scanner and clear the computer and it will run fine for anywhere from one to twenty miles. And the only code I'm getting is p0140 which is o2 sensor which I was told it shouldn't effect my drivability. I just got done replacing the cpi spider injectors with the upgraded mpfi injectors and I thought this would fix the problem but it didn't. Also have a new catalytic converter, muffler, cap, rotor, plugs and wires.

Also it seems to be worse when its wet outside, muggy rain etc.

What do you guys think? Where can I start looking or tests that I could do to rule out certain parts

 

try replacing your ignition control module...when it starts to go bad it hates moisture and gives no OBDII codes

 

Automotive Technical Service Bulletin - TSB | Engine-Codes.com

 

if clearing the codes helps then i would imagine its the O2 sensor. If they go bad (depending on which one) they will do funny things with your fuel mixture making you get horrible gas mileage and run bad. But it running bad when raining can be a separate problem all together. Like was said earlier the ICM doesnt like moisture when its bad and neither do the plug wires (if you didnt use AC Delco).

You can test this by taking a misting spray bottle out with you when its dark out and spray the plug wires and ICM while the engine is running. If you see a blue light show between the wires then you have a problem.

 

Ok replaced the distributor, and it seems to run better. But the biggest problem I'm having is after a hard acceleration my mpgs will drop to 10ish and the slight jerk when I let off the gas is still there. It accelerates normally and shifts normally.

Also i did not use acdelco plugs or wires could this be my problem?

And the only codes it has thrown have been p0155(o2 sensor) but it went away and p0140(o2 sensor) which has been going on and off (mostly on) for 2years

 

Unplugged that o2 sensor and it has been running great since with the SES light on. Replaced the distributor and spider which were bad and this blazer is running awesome. Multiple problems suck!!!

 

Are you still running with the o2 unplugged? Also AcDelco plugs work best in these engines. Wires you can get away with.

 

Why not replace the O2 sensors? Pretty easy to get to.....at least easier than the distributor.