I have a 1994 Chevy S-10 Blazer 4.3/ V6 CPI that has become a yard ornament... We can't seem to figure this thing out! Late last summer I changed the plugs & wires & it suddenly began running really bad (missing hard, back firing, etc)... Must have been a bad plug because another plug change solved the problem, but then it started running rough again... Since then, it won't even start at all now... The last time I had it running & was able to drive it, it would surge while driving & holding steady on the gas & was so close to dying at all times that the brakes didn't even want to work right... The check engine light had come on the last time I drove it so I ran the diagnostic codes & it gave one code, for the EGR valve... We replaced that & it still won't start... Turns over fine, but won't fire... It has fuel & spark, it should start.... You'd think... Here's what we've done to it...

Replaced: plugs & wires, distributor cap & rotor, ignition control module, EGR valve, all vacuum lines, fuel pump & filter, catalytic converter...

Plugs are gas fouled...

We're stumped now.... Not sure where to go from here.... Any insight would be so greatly appreciated.... I'm almost ready to give up & sell it, but I know as sure as I do someone will replace some simple part & have an awesome Blazer...

 

have you checked it since for new codes? Have you checked to make sure it is getting spark? kind of a shot in the dark but the timing could be off does it spit, sputter, or backfire when you try to start it out just smoothly crank?

 

Check fuel pressure and leakdown. When you initially turn the ignition to the RUN position, (engine off) the fuel pump will activate for ~2 seconds and then shut off. Fuel pressure must be checked during this 2 second time frame. Pressure must be 55psi to 61psi and must remain above 50psi for at least 10 minutes after the pump shuts off. post your results.

Most auto parts stores rent/sell/loan pressure testers. The service port is located next to the distributor, on the driver side:

 

Hey i found this it may help https://blazerforum.com/forum/engine...not-run-45944/ in the mean time I'm sure your in good hands with the captain he'll probably walk you right through to your problem these guys are very knowledgeable good luck.

 

Zack, that's a great link.... for 96 & newer CSFI systems. Not so much for the OP's 94 CMFI system (different diagnostics).

 

It does have a new fuel pump & filter... Just replaced them 2 weeks ago... Even with these new could the fuel pressure be off? Is there some other component that regulates the pressure? There IS fuel to that port thing at the back of the engine...

 

Your 94 does have a fuel pressure regulator, it also has two fuel lines in the plenum that like to spring leaks. Testing fuel pressure and leakdown with a tester will tell us if the fuel delivery system is pressurizing the system adequately, and if the system can hold the pressure, it must do both.

 

Thanks for pointing that out I didn't notice. I'll go back into my corner and pretend I'm not stupid.

 

No problem Zack, I miss stuff too, slap me when I do

 

Any update to your mysterious issue?

I have a similar problem with my '01 Jimmy. I get a random misfire code, a rough idle, and it usually backfires within about 60 seconds, usually starts popping first. A couple days prior, I had started it with a rag in the end of a loose intake tube, but it ran great, even when revved up and also while idling. Then I installed new sway bar bushing kit, finished installing K&N intake, and flashed the ECU (which I have flashed back to stock to diagnose the problem); It ran as mentioned when I then started it. Although I later found a rag in the engine compartment below the tube opening (as if it fell out), I am suspecting there may have been another rag. I looked into the upper intake plenum with a light and mirror, but couldn't see a rag, though it was hard to see well. I was told the red shop rag likely couldn't have gotten far if it was sucked up. Likewise, if I sucked up a rag, it wouldn't explain how everything ran so well during the run when the rag would have been sucked up. I am getting a camera probe later this week to get a better look. I have new MSD 8.5mm wires and a used Accel cap and rotor from my last Blazer. The cap and rotor have less than 5,000 miles on them, but I cleaned them very well anyway, with no effect. The cap had no apparent defect, e.g., a hairline crack, but the rotor's brass piece looked dull (I sanded the whole tip area down to clean shiny metal). Unplugging the MAF sensor seems to help a bit, and it was not on at all during the run when I may have sucked up the rag. I also am using new Bosch Ir Fusion plugs, an Accel coil, and an MSD 6-AL ignition, which I successfully bypassed to test, but to no avail. I also installed a new Delco fuel fump and filter a couple months ago and the fuel system tested fine, but I will check again for the hell of it. I have not examined a plug yet, but I suppose I should to get an indication of what is going on. I'm thinking the timing is causing the detonation, or maybe intermittent spark that is ineffective causing flooding which eventually ignites. Although I had the cap and rotor off, that shouldn't disturb timing. I flashed the ECU, but the timing mods were very minor, and I flashed it back to stock anyway. One other thing: I sprayed everything in the engine compartment with WD-40 to prevent corrosion of plastic/metal/rubber. I was thinking I may have shorted a sensor with the spray, though this has never been a problem in the past. But what sensor? The fact that there is no specific cylinder for the misfire leads me to believe there is a simple malfunction with a primary spark/fuel apparatus, but I can't seem to pinpoint it. I made no major changes to those systems and yet suddenly it started running terrible. I was thinking of testing with a new ECU, though I don't suspect that will solve anything. It runs better at higher RPM, but I'm guessing that is naturally the case. Any tips would be appreciated. Thanks!

P.S. - I'm thinking this should be a new post, but it relates to the OP, so I am not sure. I am new, and I apologize if I made the wrong decision. https://blazerforum.com/forum/images...flamethrow.gif