GMC Repair: 94 Jimmy running rich, mass flow sensor, fuel pressure regulator

Question
I have a 1994 GMC Jimmy, 4.3L V6 Vortec engine, 4-spd. A/T. Recently the fuel pump and water pump have been replaced.

When it is at an idle, it idles very rough.  When you press on the accelerator from a stop, it hesitates for a second then goes.  It runs normally when accelerating or a constant speed. The bad idle caused the Service Engine Soon light to turn on. It also is running very rich.  The bad idle began a day after the water pump was replaced and a week after the fuel pump replacement.  

I initially thought it was a vacuum leak.  I found a hole in the hose off of the PCV Valve and replaced the hose.  That made it run worse.  I checked the PCV valve and it appears to be operating properly (I watched the valve being sucked in and out).  The valve rattled when I shook it.  This only tells me that the hole in the hose was allowing for air to be sucked in with less resistance than through the pcv valve alone.

I have checked all electrical connections and hoses.  Everything is securely fastened with no broken wires or leaks

Could the installation of the new fuel pump have caused something else already weakened to fail?  Could the fuel pump be supplying too much pressure?

What is the operating fuel pressure and how would I check it?

Are these symptoms of a failed ERG valve or mass flow sensor?

Answer
Could be a faulty FUEL PRESSURE REGULATOR.

Could be a vacuum leak or incorrect vacuum hose routing when water pump was installed.

Could be almost anything.

Is the check engine light illuminated on the dash ?.


You stated: "I found a hole in the hose off of the PCV
            Valve and replaced the hose.

            This does NOT sound right.


check your vacuum lines for proper routing as there should be a vacuum routing sticker pasted under the hood.

e-mail me a pic of this hose to:

onlineautohelp@msn.com



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