Van idles fine when excellerating van loses power lopes@will not go over 10 mph

Check the Idle Air Control (IAC) valve.

2003 Chevy Trailblazer-CHECK ENGINE LIGHT AND REDUCED ENGINE POWER ...

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Dec 23, 2011 - 2003 Chevy Trailblazer-CHECK ENGINE LIGHT AND REDUCEDENGINE POWER ... The reduced engine power ligth comes on and I lose power. ...Next, the fan clutch failed -- which is when he did an "above and beyond" .... yesterday I have not replaced anything bc they have told me nothing is wrong.

Not quite everything is fine.
Is the check engine light on ?
When you push on the gas pedal, does the engine speed change ?
Can you rev up the engine in park ?
What have you checked so far ?

Try cleaning the mass air flow meter. There;s a spray cleaner you can get at an auto parts store

1. Vacuum leakage Check throttle body and intake manifold for tightness. check all vacuum hoses.
2. Faulty fuel or pump or electrical.
3. Plugged PVC valve.
4. Air filter clogged
5. Leaking head gasket.
6. Camshaft lobs worn.
All of these porblems can cause lopes or erratic idle.

check for back pressure on exchaust can be stopped up

could be idle air control valve

I had a similiar problem on my 1999 Dodge Ram 1500 Conversion Van. It ended up being a partial collapse of the catalytic converter which didn't allow adequate exhaust. The problem only showed itself because I could not get over 55 mph going up a small hill.

Hi,
The air cleaner mighty be clogged causing insufficient air supply. That is why it runs fine on idle because less air is needed and when the engine demands for more air, there isn't enough.

Things to check
timing
ignition system: coil, plugs,rotor,cap, lead wires
dirty injectors
fuel pressure
air filterfuel filter
EGR system
air leaks at throttle body and manifold