1995 Chevy Silverado Lean popping at load or low accellerat

SPEEDYCATO

MEMBER
1995 CHEVROLET SILVERADO
V8
4WD
AUTOMATIC
211,000 MILES

I am having the same problem on two trucks. At low speeds as you accelerate it starts popping thru the intake. I have replaced fuel pump, fuel filter, iac, map, ect, icm, coil, pickup coil in dist., Tps, cap, rotor, wires, plugs, checked compression, leak down, everything that I can think of. Truck idles smooth and once you get past the low end stumble it runs strong and clean.?

2 Replies

SPEEDYCATO

MEMBER
11 POSTS

See post above

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Sunday, August 30th, 2009 AT 10:11 PM

MERLIN2021

MECHANIC
17,250 POSTS

Have you read the codes? MIL on or off, and does it come on with key in on positin? Then go out after a few seconds? Also check this.
Exhaust System Backpressure Before replacing any components, check exhaust system for restrictions. Use a vacuum gauge or a low-pressure (1-5 psi) pressure gauge to check exhaust system. If using a vacuum gauge, connect gauge to intake manifold vacuum, and start engine. Observe gauge while holding throttle steady at 2000-2500 RPM. If vacuum gauge reading slowly drops after stabilizing, exhaust system may be restricted. Check At Oxygen Sensor Remove oxygen sensor. Install backpressure tester in place of oxygen sensor. After test is completed, coat oxygen sensor threads with anti-seize compound before installation. Diagnosis 1. Start engine and bring to operating temperature. Increase engine speed to 2000-2500 RPM. Note gauge. Exhaust system is restricted if reading exceeds 1.25 psi (.09 kg/cm 2 ). 2. Check exhaust system for collapsed pipe, heat distress and possible internal muffler failure. If none of these conditions exists, check for restricted catalytic converter. Replace as required.
Bacfiring up through the intake can also mean a worn camshaft. Use the vacuum gauge and take reading at idle, should be 18-22hg and steady.