I posted this in the Gasser section without much support, so I thought I would try it here where the real handshakers hang out.

My daughter has a '97 Chevy C2500 equipped with a 350 and 5 speed (the Brotherhood (Sisterhood) of Handshakers is alive and well in our family). I've driven it to work this week and noticed when letting off of the accelerator, the engine doesn't slow down. If I slip the transmission into neutral (w/o pushing in on the clutch), the tach will maintain the RPMs at the "pre neutral" level. If I push in on the clutch a little, the tach will drop. I figure this has something to do with emission controls or some other crap as that. What I want to know is HOW DO YOU DEFEAT THIS FEATURE?

Thanks,
Mark

Hey Max it is TBI right? It sounds like the TPS?

By TBI you mean throttle body injection, no it has the port injection. I had a '92 with TBI that I drove for a couple of years that did this. It really pisses me off. I like the way the DMax RPM's drop when you let off the throttle, makes it really easy to shift w/o the clutch.

This '97 is impossible to shift w/o the clutch. Also from a safety issue, when you let off the throttle to just coast, the RPMs do not drop until you push the brake or clutch. This could be a safety issue for my daughter as she is a new driver.

Any help would be greatly appreciated.

I think the port injection still has the throttle position sensor. I think is a result of the slow processing of the older TPS. It prevents hard deceleration from a dead let off, if it didn't control this it would cause greater wear on the hard parts...drive line, gears etc u-joints. I don't know if there is anything you can do other than mapping the fuel curve via if that is even possible?

Ok thanks...The more I drive the truck the more accustomed I am becoming to its manners. I find a simple touch of the brake or clutch and the RPM's will drop pretty quick. Should get my DMax back tomorrow, can't wait!

Thanks again for the help.

Mark

same problem here on dad's rig, we will be trying a TPS and maybe an IAC valve.

same problem here on dad's rig, we will be trying a TPS and maybe an IAC valve.

GM Guy,

Let me know what you have done to fix the problem. I noticed that if I push in on the clutch, the RPMs drop. I haven't looked at the neutral switch on the clutch to see how many wires are on it. I'm wondering if there is a wire that I could jump or disable that fools the engine into thinking the clutch is depressed? Just a thought, will look at this over the upcoming weekend.

GM Guy,

Let me know what you have done to fix the problem. I noticed that if I push in on the clutch, the RPMs drop. I haven't looked at the neutral switch on the clutch to see how many wires are on it. I'm wondering if there is a wire that I could jump or disable that fools the engine into thinking the clutch is depressed? Just a thought, will look at this over the upcoming weekend.

If you have cruise, jumping/disabling wires will make cruise inoperable. We will not be playing on it till spring, when we need the truck, and it is nice weather for wrenching.