Well, where to start....... I've got a 97 4wd 4d blazer 133k miles and I'm not even sure where to start the diagnostic. When the engine reaches a "higher than normal" RPM (like if you are trying to pass someone or quickly get up to speed after turning onto a road and someone is bearing down on you etc...), I feel an extreme loss of power (to the point of actually loosing speed). When I this occurs, the coolant temp starts to rise quickly (goes to 210 from about 1/8 of the gauge lower which I assume is about 180ish), and the lights dim out alot. If I back out of the throttle to a more "normal" rate of acceleration, everything goes back to normal.

I tried testing it by manually shifting the trans to a lower gear and accelerating slowly, and I get the same results (when it reaches the higher RPM it acts up). So It doesn't matter where the gas pedal is in it's range of motion (appears to be an RPM based problem).
The Blazer will run just fine as long as you drive it ....... like a soccer mom, but if you want to pass anyone you better have plenty of room so you can increase your speed slowly.

Also I'm not sure if it is related, but it starts one of 2 ways...... nearly as soon as the key is turned, or after cranking for about 2.5 seconds. never anywhere in between, and it doesn't really matter hot or cold. sometimes it starts one way, andsometimes the other. It also doesn't matter if I let the fuel pump run first or not before cranking.

I know I need to check the plugs and wires, but the cap and rotor have been replaced (cracked cap) and the MAF sensor hasbeen cleaned.

I hope with these details someone will have a good idea what could be wrong. Thanks in advance.

 

is your catylitic converter pluged up

 

well, I dissmissed that early on (symptoms not matching what others said), but I may have to check into that. I just did a search and found ivannj's threadand it sounds a lot like the problem.

I'm going to check that tomorrow, but if anyone has any other ideas I'm listening.

 

I'm no expert but you could be running out of fuel in the higher rpm, going lean which can lead to a heating issue with the motor. Can you put a fuel pressure guage on and see if it loses pressure when you get on it? I'm having a power loss issue at passing rpms as well and for me it's fuel pressure but i dont' have the accompanying rise in coolant temp...that i've noticed.

 

That is what I was leaning to, but I've still got to try and get a gauge to test it with (the parts store I went to last night didn't carry them).

 

Well I went out and beat on my cat (the converter on the blazer, not the pet ), and it sounded like it would if it had 1 or 2 pea size peices of gravel in it (very little noise at all, but I could hear a tiny bit). So I guess my next step is to yank the cat and see if I can clean it out.

 

Sounds more to the fuel side of things, but as far as the lights dimming to what extent is alot because that might be a sign of electrical problems. How long since your last fuel filter change?

 

I'm not sure about the fuel filter (I have only had it for about 1k miles), but it is one of the next items on my list along with plugs and wires.

As far as how much the lights dim, it is like when you put a heavy load on the system (kinda like starting the engine with the dash lights on and they get dim due tostarter draw, or turning the dash lights down about 3/4 to 1/2 way down).

 

I would replace the fuel filter, then use a gauge to monitor the fuel pressure at the RPM where the condition presents itself.

And you do not clean a catalytic converter. You have to replace it.

 

By clean I meant gut, if that is even possible. I'm on a real tight budget and hate to spend the money on a new one if I can "cheat" my way around it. We don't have any kind of emissions check where I live, so cats getting cut out and thrown away are a somewhat common thing (I guess mostly on the older cars though because of theo2 sensors).