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Re: Runs good cold but loses power and hesitates when...
Classic signs of a plugged catalytic converter ... I would have a exhaust shop check it out for you , the newer aftermarket design is much less of a problem than the old pancake style and fairly cheap.
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It could be low fuel pressure from a weak pump. A fuel pressure test would find out. When the engine is cold, the computer keeps the injectors open longer-a cold engine needs more gas to run than a warm one. When at normal operating temperature, the computer matches the gas to the incoming air. If you have low fuel pressure against the injectors, that is when you would notice the hesitation. A possibility anyway. If fuel pressure is good, check for trouble codes. A sensor may be sending the wrong information. Could be the mass air flow sensor-the one that tells the computer how much air is coming in so it can match the right amount of gas for it-through the injector on-time. There it is, your injector pulse width is too narrow. Causes lean running, stumbling, hesitation. Another possibility. Check for codes first. If not air or gas related (is your air filter clean? And the gas filter been changed in the last 2 or 3 years?), and no codes, and fuel pressure is good, you may have to keep looking for an electrical fault. If it runs good when cold, doesn't seem likely to be a mechanical fault.
The EGR valve is closed when the engine is cold and should open when warmed up. Have all componets check to see if they are functiong correctly. Auto Zone provides a free computer scan at no charge . They will avise you what is in need or replacing and how much for the part. These parts are easily installed too
I had this problem also and it turned out to be related to the cold start system. cant remember the part name but it was causing the hesitation problem.
That's probably the problem the broken wires.
The 02 sensors send a rich/lean signal to the ecm. If they aren't working right, a lean or rich situation will occur. Best to get the wires fixed. If the wires broke off at the sensor, need to replace it.
Could be aging ignition cables letting you know that winter is coming and the condensation that can form overnight can invade cracks that can bleed off some of the high voltage you need at the spark plugs.
After the engine is warm, leaky cables can temporarily 'heal,' drying out and losing less than when cold.
If they are sufficiently bad, sometimes you can see some sparkling going on under the hood if you park in a dark area.
If you have 50k on your plugs, it may be time to replace those too.
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