1995 Blazer MAF/O2 sensor/EGR valve problems

If someone would be kind enough to help with troubleshooting this issue, I'd be extremely grateful. I'm trying to assist a friend and I don't access to the Blazer. But here's what I know: The Blazer is the 4.3L 4WD (I think she said Vortec). The gas mileage is down to about 10 MPG. The computer is spitting out the codes for: MAF/O2 sensor/EGR valve errors. From what I understand, ONE O2 sensor was changed (I heard there are more), and the EGR valve was replaced. This did not fix the problem. I don't work on cars much but I have aircraft maintenance background and can follow your instructions or a manual, etc. I'm just looking for a logical flow of troubleshooting for this Blazer so that I can help her out because it's been a problem that no one has been able to help with yet. Any help that you all could give would be GREATLY appreciated. Thanks in advance. Mike in Ohio

With those codes and that gas mileage, I'd start by checking out the CPI and nut kit. You can find info in these threads:

http://www.automotiveforums.com/vbulletin/showthread.php?t=462726

http://www.automotiveforums.com/vbulletin/showthread.php?t=473110

http://www.automotiveforums.com/vbulletin/showthread.php?t=503238


What kind of problems is she having? Hard starting... rough idle..... stalling...loss of power....gas smell?

When was the last time that a tuneup was done? Spark plugs, wires, cap, rotor, fuel filter, and air filter?

Re: your questions Blazee - "What kind of problems is she having? Hard starting... rough idle..... stalling...loss of power....gas smell?"

Some hard starting, it has rough idle, has only stalled once or twice, loss of power (losing rpm's) and strong gas smell, sometimes kinda like an egg smell or sulfur smell from exhaust pipe and very poor gas mileage.
Sluggish - when pushing gas pedal down, the RPMs go up for about 5-10 seconds and then they come back down.
Most of the time it starts ok, but occasionally you have to crank it for a while and pump the gas to get it started.

Re: your questions: "When was the last time that a tuneup was done? Spark plugs, wires, cap, rotor, fuel filter, and air filter?"

Last time for tuneup was approx, 2 months ago, included all above except fuel filter I think and air filter, air filter was good.

I'd still suspect a leaking CPI (Central Port Injector) and/or Nut Kit (internal fuel lines). Remove the IMTV (Intake Manifold Tuning Valve) from the intake manifold. Once the IMTV unit is removed, visually inspect the inside of intake manifold. The manifold and injector unit should be very carboned up and dirty. Any clean areas indicate a fuel leak internal to the manifold plenum. Most times this is caused by the fuel pressure regulator leaking fuel from vent hole in the regulator body. Clean spots on the passenger side indicate a leaking CPI. Clean spots on the driver's side indicate a leaking nut kit.
It may be necessary to pull the upper plenum to see any leaks. If you do find leaks, the vehicle should not be driven until the problem is fixed, because the fuel will leak down into the oil and can cause permanent engine damage.

Blazee,
Is this the only way to get fuel into the oil !!

Although I am not Blazee, yes, on a CPI engine, the CPI injector will rupture or the nut kit which is the fuel lines supplying fuel to the injector will leak.

DO NOT CONTINUE TO DRIVE IT LIKE THIS.

EXTREME WEAR AND ENGINE DAMAGE.