[krazybaddude]

Ok, first of all, I have an 89 blazer 4.3L. Heres the problem. And this sux, cuz I just found this site, and now when i decide to post about this, it wont do it........ But anyway, around 10-15 MPH, and 1400-1500 RPM, it wants to hesitate, and it almost feels like its not getting gas. I have to push the pedal more than i should have to at that speed and rpm combo (and when its bad, sometimes that doesnt even help much).

This only happens when it wants to, and tonite, when i took it for a spin, it ran great, ........so i dunno.

Work recently performed: Tune-up about 2-3000 miles ago, (including fuel filter). New lines from sending unit to filter. New(old from junker) sending unit/line assy(old one had holes in the pressure line) and new strainer. Same fuel pump.

Hope somebody can help, cuz when it does decide to do this, its really bad.

Thanks,

-Dan-

 

[94badazz]

check spark plugs and wires, but it says you just did a tune up so i dunno? check all the small stuff... sounds like a small problem!

 

[meeh350]

mine was doing something similar to that. at small changes in throttle just above idle it would kind of hesitate then all of a sudden it would take off. It later got worse and on interstate hills at low throttle positions i couldn't get any power..... kick it down and let it shift back up and it was fine...
put a TPS on it to no avail and then a map sensor.... works fine now

other things to check would be
EGR operating properly and clean
Fuel Pressure

 

[krazybaddude]

See this is where it gets kinda weird. You mentioned "EGR operating properly" Well, at one point, the EGR solenoid went bad, causing an intake vacuum leak, so at that point(i didnt have money for the solenoid), i just plugged the vacuum line, and disabled the EGR (ran fine). Then i got a junker solenoid, and put it on, and when i revved up to like 1500-2000 RPM, in closed loop mode, the EGR still didnt open (EGR works fine, vacuum tested it). I havent played around with it lately, but i assume the EGR still isnt opening.......

This is weird because it doesnt hesitate all the time. like the last few days, no problems at all. Maybe a bad MAP sensor will do this?

 

[krazybaddude]

update

Ok, heres an update.

I just got done testing sensors out in the freezing cold and heres what i found.

TPS: .70v - 4.7v - steady increase - no choppiness or missing
MAP(output): Ign. on: 4.8v Idle: 1.5v Fast throttle open: 3.6v max. (always drops back to 1.5v)


I also checked for power going to the EGR solenoid, because my EGR wont open. (engine in closed loop, tach up to 3K.... wont open). The only power I have going to the EGR solenoid, is battery voltage (14.2v)(left pin). The middle pin has nothing at all, under any circumstances. The right pin has a 200 millivolt increase under any change in throttle. (none of this is enough to energize a magnetic solenoid......)


Oh yeah, i forgot to mention, the temperature gauge (digital) usually reads 215, and sometimes it will even go up to 230, and on rare occasion, it will go up to 245, or 260. But the thing is, the engine is not overheating.
Now i thought that a bad temp sensor would cause the gauge to read nothing, or waaayyy to high, like off the scale. I didnt think it would read a little high or low......


Well, sorry for the long post, just trying to get all of the information up.


Please help!!! I'm at a total loss here. This is driving me crazy!!
Thanks in advance ....

Dan

 

[Matt 4.3 TBI]

For the temp gauge, I would change the sensor. It's in the passenger side head, with one green wire going to it. That sensor is for the gauge only, the one in the intake manifold is for the ECM. They're both in the water jacket so put some teflon tape on the new ones and expect a puddle under your truck.