I have a 2000 Blazer 4.3 125k

Very recently it started misfiring at highway speeds. Now ryme or reason just suddenly it misses. I went over and check the codes on it today and have no codes at all.

Other problems (maybe unrelated)

Brake lights don't work (high light works fine)
Fuel gage jumps around all the time
Temp gage goes to 0 every time it misses

local mechanic suspects the fuel pump

any thoughts?

 

try peeking at this bad boy

 

I actually read his earlier and again now but like I said I have no stored codes at all

 

when your misfire is happening @ highway speeds, do you happen to notice which way your tach is jumping?

pay really close attention to the movement, 'cause it's gonna be really slight.

 

what happens when you rev it up in neutral? does it misfire then? and does it also misfire at idle? there could be lots of things causing a misfire. you should hook upi a code scanner reader and go into the timing mode and see if the timing is jumping around.

 

Use an old, clean spray bottle filled with water to mist down your wires with the engine running, at night, no other lights on. Pay particular attention to the driver side of the engine near the temperature sending unit. You are looking for sparks escaping the spark plug wires. If the wires are leaking spark, you'll get a light show.

As far as your fuel gauge goes, it likely is the start of the pump going. Fuel gauge issues are sometimes precursors to a fuel pump failure.

Your brake lights - well, that is likely a faulty multifunction switch. More specifically, the hazard switch inside the multifunction switch. You can sometimes get lucky by just replacing the hazard switch if the damage has not extended into the rest of the multifunction switch.

 

Tach moves down when it misses. (from 2k to 1800)

When you rev in n it does not miss. Also does not mis when you floor it.


By looking for the spark you are thinking that the spark is jumping from the plug wire to the temp gage/wire. Interesting, will give that a try.

I did install a new rotor and cap today. Probably moved the wire and it wont do it now.....

 

ok, the drop in RPM doesn't go with what i was going after.

Quote:

Originally Posted by 0ut1aw

..........I did install a new rotor and cap today. Probably moved the wire and it wont do it now....

on the contrary, it could actually make it worse.

when my youngest brother bought his '94 Jimmy last month, it ran like a Swiss watch-super clean exhaust smell, no shake or pop. i removed the cap to see how bad it was-it was really bad-and when i put it back on, as i was just inspecting, so i haden't ordered a new one yet, it ran like a bag of s**t! thought, ahhh figures! i disturbed the build up of corrosion!! put a new cap/rotor on the next night, same problem-even worse! no arcing from the wires either!! but these wires didn't look new, didn't look really bad either, but i changed them anyways and problem solved.

 

Well, either the new rotor and cap or my moving wires around or both seems to have fixed it for now. 48 hours driving like normal and it seems ok.

I am pretty sure the spark jumping to the temp gage was at least part of the problem. The rotor and cap did give the power band new life...

Now on to the brake lights. Pretty sure I will need to replace the entire blinker assembly

The hazard switch will not press and the b;linkers no bl;ink when it is cold outside.