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Q: The car is from California and the smog pump was removed, runs poorly.

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The car runs good when cold but as soon as it starts to warm up it runs poorly. My mechanic says that it is like it is not getting enough gas.He has changed injectors as someone used silicon and injectors were clogged. O2 sensor changed as it was bad.The coil was changed as it to was bad. The fuel pump was changed as was the hose to the mass air intake. Can you think of what it may be?

My car has 189000 miles.
My car has an automatic transmission.

Hello. I think your mechanic is on the right track. Check fuel pressure while running to make sure fuel pressure and supply are adequate. If so, start with verifying solid tune-up basics; solid spark and fuel injection performance without misfiring. If these pass the test, it’s possible your catalytic converter is clogged - you mention silicates and other contaminants, and your truck has quite a few miles. The air from the secondary air pump (that’s what a "smog" pump is) was to help unburned fuel burn in the cat. If it is no longer there, any unburned fuel will eventually clog the cat. If you’d like a second opinion on this issue, have one of our mobile technicians come to your location and diagnose your rough running symptoms firsthand.

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