First Chevy Truck

I have a 93 Chevy C1500 pickup automatic with 4.3 -Z (non Vortec) It has 68,000 miles. It is very sluggish when accelerating, and shifts hard from one gear to another. It doesn’t run rough (neither cold nor hot) and does not surge, backfire or “ping”. No blue, white or black smoke from the exhaust. The lock-up converter kicks in at about 50 mph., but the truck seems to struggle more when I try to keep a constant speed between 40 and 45 mph either before the lock-up kicks in or when I drop it back to 40-45 after locking up. I can get it to run at 65-70 mph on the highway but I have to keep good pressure on the pedal as it seems to be working hard at that speed.
When I disconnect the EGR valve and plug the vacuum line from the solenoid it runs perfectly and shifts very smoothly, just like a new truck, but the SES comes on after driving a few miles at 55+ mph. It goes out when idling for a few minutes at a red light.
I have replaced the plugs, distr. cap, rotor, ignition coil, O2 sensor, spark plug wires, gas filter, cat converter (whole new exhaust system).
I enjoy tinkering with minor mechanical repairs, but what should I try first? The EGR?… EGR solenoid?… MAP sensor?… Any suggestions, other that bringing it to a shop for a diagnostic check? Thanks for your advice… anyone?

jsloan@rimslegend

It can be something with the tranny try throwing in some Lucas for the transmission it only cost 15 bucks hell it's worth the shot

http://www.rimslegend.com

wmiller

I have no suggestions for you, but I am subbing because this sounds ALOT like my 4.3 Vortec. I have replaced almost everything you have and I get the rough running at 40-45, the hard working 65-70, and the SES after cruise for awhile at highway speed. I will have to try unplugging the EGR sometime to see if that helps...

First Chevy Truck

Hi, wmiller. Hopefully we'll get this resolved. What seems to be different in our issues is that you get the SES light with the EGR connected. I get it only if disconnected, which is to be expected. I'm really happy about the current performance unconnected, but I don't like the SES light. Also, a more serious problem could come up triggering the light, but I would be ignoring it thinking that it's just my EGR.

You didn't mention what year your vehicle is. If it has OBD I, AutoZone showed me how to retrieve the code for the SES error. It's really easy (takes seconds at NO cost). You can find it on the net by Googling "OBD 1 codes retrieval" . If you have OBD II, then you'll need to beg or borrow to plug a scanner into the OBD port and get the code. I think AutoZone does that for free too. The code will tell you what's acting up.