Hello all, just joined hope you can help me out. I'm looking into a 1992 blazer a friend of mine has. It has some issues that we can't figure out. When it's cold (<45 degrees) outside the truck runs great, lots of power. When the temperature is above 45 or so the truck runs horribly, surges, hesitates, acts like it's gonna stall, ect... He's replaced some sensors, I know of the MAP sensor for sure, and it isn't overheating. Any ideas??

 

Welcome to the forum.
Can you give us a little more info to go on, other than it's a 92 blazer. The more vehicle info and history of what's been done (including codes if possible) the better.

 

Thanks for the reply, sory about that.... I was wrong, it's a 1994 ( not 92 ) S-10 Blazer 4 dr, 4.3 v6, auto, 4x4, @ 100K miles. Radiator blew a couple months ago, it was replaced, along with new belts, hoses, and thermostat. He figured do it while he could get to it easier with radiator out of the way. Now the truck runs great when it's cold out, no problems really. However when it gets warmer out ( above 45 ) the truck starts running bad, looses power, acts like it wont take the gas, can't get or maintain any speed, and will die on you, like never starts back up, and when it does you limp home very slowly ( unless its gotten really cold out, then you drive home fine). He replaced the MAP sensor and the coolant temp sensor that I know of. Oh, yeah, the engine isn't overheating. Any ideas?

 

You've got me stumped at the moment.....any codes?
You might have to have it diagnosed with a scanner while the problem is happening.

Hopefully someone else will come up with an idea for you.

 

I checked the codes today and it only flashed a 12, ithink thats just a default testing code. Can't really take it anywhere to have it scanned, truck is an hour away from anywhere (out in the sticks if you know what I mean, lol). I did notice today that when you switsh the key on the fuel pump hums abnormally loudly, not that it is loud, just you have NO problem hearing it. My other vehicles you can't hear the pump unless you are beside the tank. Dont know if that could be a problem or not.

 

just put a new fuel pump/sending unit/relay all in my '94 about 2 months ago, it's def. not hard to hear it running. a lot of what you describe is how mine was acting a few weeks back turned out to be a bad fuel pressure regulator for me, i'd suggest testing the fuel pressure as a first step to see if there is an internal leak.

 

Code 12 is telling you that the computer is communicating and it can see no problem.
The fuel pump is a possibility, but I would check the running fuel pressure before replacing it.

I'm still stumped as to why the problem is temp related.

 

I am really leanin more on the fuel system as a cause of the problem. Get the runnin fuel pressure like what was said before and let us know what you get!!