95 s10 blazer 4.3 vortec vin w rough idle

Asked by Jan 09, 2016 at 08:22 AM about the 1995 Chevrolet Blazer LS 4-Door RWD

Question type: Maintenance & Repair

I'm still working on my 95 s10 blazer 4.3 vortec vin
4 it is idling  rough & fouling  plugs with black Sutt
but is will rib up acts like the mass air flow sensor
but don't have one I changed the o2 & intake air
temperature sensor sometime it will level out do u
think it could  be egr r tps sensors no engine light
on  I Changed the map sensor knock sensor on
one side but not the driver side please help

1 Answer

21,855

There is only one map and knock sensor... sounds like an internal fuel leak. Either the regulator is leaking or the lines inside the plenum going to the fuel injector spider is leaking, those lines are referred to as a nut kit. This can be tested for by checking fuel pressure and leak down rate. It shouldn't leak down much if any over 5 min. If you don't have a tester cycle the key a few times to allow the pump to run, turn it off and wait 2 min. The go behind the intake and press the Schrader valve on the fuel line, if no fuel comes out then your fuel pressure is leaking down. Take the upper intake off and look for clean spots, that's where the leak is. Everything should look dirty and black

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