I just bought a 93 chevy s10 last week. It has ~250,000 miles on it. Once the engine reaches ~190 degrees it begins to bog down and intermittently backfire in the lower gears during take off. If I floor it it will downshift no prob and truck it to cruising speed and accelerate better. It is more pronounced when the temp outside is warmer.

I have already changed
1. air filter
2. temp guage
3. Thermostat, this was a problem but didn't seem to help the power loss
4. Fuel filter
5. distributor cap, cables and button

It idles great and sounds clean. I looked through many forum topics posted here and couldn't find anything similar to this. My next thought is EGR and PCV, then on to more expensive things like catalytic converter. Could anyone give me a little better direction than throwing parts at it. Oh one more thing, Last owner may have let it sit unattended for a while. Thanks

 

How old are the spark plugs? Have you checked for any vacuum leaks or the fuel pressure to see if your pump is going bad?

 

I forgot to post it but yes I changed the plugs, no check engine light but I will check the codes and vacuum pressure this week and post what I find, thanks for your replies.

 

I was reading through the manual again and found that the EGR can cause symptoms like my own. Didn't have a chance to hook it up to a diagnostic tool. I pulled off the EGR and sure enough it was corroded, warn and gunk was clogging it up to the point it whistled when I pushed it in. I changed it out and it has ran great ever since. Although my problem could have been a combination of the above mentioned components I think it is running great now.

 

Thanks for the update, glad you got it running good again

 

I was gonna say EGR or O2 sensor!