Hey guys, I have a 92 S-10 Blazer (4.3L V6). This thing has been a champ and have never had any problems with it. I pulled in the driveway the other night and it was running fine, started it the next morning and it had a horrible misfire. It was getting close to needing a tune-up anyways so I did that first. Changed spark plugs, wires (including the short one to the coil), cap/rotor, fuel filter. No change at all. I have an OBD1 code reader, and though it was not throwing a check engine light it came back as a "low voltage to TPS sensor" I replaced the sensor but no change. I have also taken a volt meter to the connector to ensure proper voltage was getting sent to the sensor and that the connector was good ... everything checks out. I have a fuel pressure test kit, though I am having trouble finding it at the moment.

Any ideas or suggestions?

 

It sounds like you got the electrical part of the tune up out of the way but what about the fule and air part

How dose your air cleaner look and your fule filter when was the last time you changed that they can both give you a feeling of a miss
sometimes your car will run fine then you shut it down for a wile and the dirt in the filter go's to the bottom of the filter then when you start it it almost clogs up the filter kinda makes it feel like a miss

Double check your fireing order make sure nothing is crossed also make sure all your wires are tight if there not they can ark and make a miss try running at nite with no light look for a ark
Also make sure your Distributor isn't wet not just the cap but in the
Distributor also look for oil watter ect.....
There is also a couple of other things that can cause it like cheep parts store brand stuff verry cheep
bad groung to the block run you lites wipers and blow your horn see if your horn sounds funny could be a bad ground

This is just little stuff it could be other electrical things doing it also but you would get a code

Some times what i do to help me trouble shoot is go to a online parts place and see what is all involved with what ever im working on like Rockauto
I hope I helped if I didnt sry

 

Thank you for the reply.

I went out and checked the air filter this morning, not bad at all.
I think I'm going to replace the ignition coil today (the only part of the ignition I didn't change out), assuming the parts store is open.

I didn't check when it was dark out to see if any wires were arcing but I will as soon as the sun goes down tonight.

 

before you spend more money on parts that may be fine,go to autozone and get a fuel pressure test kit. its free,just ask for it. but they will have you put down i think $100 for security deposit. when you bring it back you get every penny back. Its a cool loaner tool system they provide.

If you have the tbi system,pressure needs to be 10-13 psi

if you have the cpi system, then it needs to be 60 psi+ at key on,and hold above 55 for 10 minutes.

if its the cpi system,Test at the inlet of the fuel filter,then the port at the engine. if its low at the filter or drops off quickly,its the pump,if it drops off at the engine,its the fpr.

 

Having the actual code helps. I know you probably interpreted it right but EVERYONE who just puts what they think it means believes they got it right.

The ECM supplies both the ref voltage and GRD to sensors. Ground is also keyed to block and frame ground. Proper check is across the TPS connector to see what the ECM is actually supplying: {probably 5v} THEN reading the GRD voltage to block and chassis. Should be no more than .1v. Now check the MAP connector to see it is getting the same supply voltage.

THEN, at ECM, read the TPS output and see it sweeps from NEAR GND to NEAR ref voltage. Will probably not be all the way to either side. IMO, within .5 volts.

 

Thanks a ton guys, all good advice. The parts store here was closed today so I didn't get any new parts but it is running much better.
I put the TPS wires back together, had to pull the loom apart to get the slack I needed. I'm not sure what was done to the wiring on the truck before I got it but all of the wires under the hood are wrapped in wire loom and taped closed. It was a county work truck at one point so it has extra wires bundled for light bars, radios, and antennas. Long story short I took it out this morning after getting everything back together and it still had a miss, with an intermittent check engine light. Would come on for 10 sec then go off, come back and go off. It almost stalled on the way back, so I gave it a good shot of throttle to get back home and it just cleared right up.
Haven't had a CEL or misfire since then. Just took it out to get some food and it's running great again. Seems like this could be a loose wire somewhere maby? Strange but I'm just glad it's working again (for the moment at least)

 

Good old fashion red neck tune up could of been carbon build up also

 

i have a 95 blazer low miles on crate motor it had bad missfire garage replaced heads put in new plugs plug wires disstuputer, cap, coil map sencer cleaned e.g.r valve fuel fillter all testing 1,300 in it so far now i have a miss at 5 2 mph right as i try to smooth out an d cruzz it goes away when i accelerate or i let off fuel

 

my 93 did the same thing. would be fine one day then blahhh the next. but it missfired really bad. turned out to be a weak ignition coil.

hears mine missfiring before i replaced the coil. at first i thought it was the injectors but well just watch the vid lol.

 

Only thing is bam that he has a 92 and I believe he is TBI and doesn't have a spider injector. I agree with the guy that told you to check fuel pressure, maybe your pump is on it's way out or the rubber fuel line in the tank that is connected to the fuel pump is going bad and leaking air. Other then that I would make sure your timming is set correctly.