Low speed miss

2003 astro-misses and chugs and clunks until i get up to 40 miles per hr

How many miles?
Has it been maintained in accordance with the manufacturer’s recommended maintenance schedule?
Have there been any other operating problems?
Has any work been done recently? Have you checked anything yet relating to this problem? If so, what?
How does it run over 40 mph?
Does it do this always, or only under cirtain conditions?

Your problem is likely from misfiring or from fuel delivery. Your answers to the questions will help us determine which is the most likely and to provide suggestions to help you get to the problem’s root cause, which will ne necessary to fix it.

does not to it when it is cold,only after about 20 minutes of driving,runs great on level,runs great over 40 mph,60,000 since last tune up

Stop by the local parts store and get the computer scanned for fault codes. Many will do this for free. Post the codes here.

Since it does not do it when cold or at high speeds, I think it’s safe to eliminate the fuel delivery as a possible cause and concentrate on metering and on ignition.

Second the same mountainbike but want to emphasize that you get the actual code, not just the diagnosis. The code will be a P followed by 4 digits, the first digit will be a zero. P0xxx.

60k seince last tune up i would tune her up

error codes p0155 p0101