Hi,

I am a newer member to the forums and this is my first post. I have read through the site to find a solution to my problem but have yet to find something solid.

I have recently purchased a 94 s10 Blazer 4x4 w/4.3L CPI Vin W. When I bought it it idled really rough after warming up to full temp so I replaced the dist. cap and rotor, plugs, wires, all filters, pvc valve and the MAP sensor along with giving it an oil change. This helped a bit but the rough idle is still there.

I tried running seafoam through the gas tank, crank case and intake manifold and it did a thorough job of cleaning out the gunk and carbon but it still did not help with the idle. I also removed the EGR valve(which seems to be in good working order although I haven't checked the EGR solenoid yet) and cleaned it out as well and the attached ports.

It does start hard when cold which tells me I will have to replace the fuel pump and sending unit soon (25-30 psi on test when I turn the key to the on position) and I do not have any gas in my oil which, from what I've read is an indication of a bad fuel pressure regulator.

The check engine light has never come on so obviously it's not throwing any codes.

My MPG is approx. 20 - 24 (10 - 15 before cleaning out the intake with seafoam)

My plug wires are ordered correctly and I made sure the gaps were good prior to installation.

Observations I've made:

When I unplug the four way vacuum tee from the back of the intake manifold the rough idle issue goes away and I can drive the truck normally but I have no cruise control or 4x4 plus I don't want to take the chance of messing something else up by driving it that way. I have chased vacuum lines and they all appear to be in good condition with no blockages.

I am at a loss right now. Any help will be greatly appreciated.

 

I also have a rough running 4.3 V-6. Replaced the Spark plug wires but problem continues. Mechanic gets no codes to id the issue. I read about the EGR solonoid and will try! Any other suggestions will help. He also wants to replace the plugs. I get pressure so don't want to replace the fuel pump unless anyone thinks I should! 109000 miles!

 

at 25-30 psi a CPI engine wont operate. They require a minimum of 50psi, spec is between 55-65. Leakdown is also important to check for.

 

Be sure to check your PCV hose connection at the PCV valve. Mine was cracked and dry-rotted. I replaced it and now it runs smooth.

 

Finally discovered the problem with my 94 Blazer 4.3 V-6 running rough! Answer: 2 dead cylinders at 105000 miles! Truck is Officially dead after $2500 of worthless investments! I stood in shock after the mechanic gave the bad news! I am thankful it died just after I drove my family to the airport. I got $500 in trade to help buy a 2005 Ford Focus...which I truly love. No more leaks and no more worries and horrible gas mileage!

 

What do you mean by saying two cylinders "dead"? How so? Just curious

 

A mechanic told you you're truck was dead because it has two dead cylinders? And I'm assuming this is after you paid the guy around $2500? Sounds like you need a new mechanic.

 

I have been dumping the $2500 into the Blazer over my 2 yr ownership and less than 2000 total miles driven. (my brother owned it up to that point). The 4WD Died, replaced trans/oil cooler lines, the exhaust, the head gasket, pvc, spark plugs harness, to mention the basics, plus a rear main that was leaking worse and worse all over the garage floor and clouds of smoke when it started up. Went to two different ASC mechanics who claimed the engine was in trouble but a costly tear down was not worth it. Finally after a couple weeks of further stammering and sputtering to the point it would hardly gain speed (exact same symptoms of a previous car that the cylinders died) I knew I was in trouble. The second certified mechanics, I trust, both agreed that the cylinders compression were bad. I have grand kids to haul around and did not want it totally crapping out on some highway! I got rid of it for $500 and found a Focus with about 95,000 and a 5 speed...which I now love driving. I know GM has had numerous problems with the 4.3 Vulcan and dumped it for the upgraded V-6. I am sad this happened but this was a time bomb about to explode!