Hello all,

I have a 1995 4.3L vortec 4x4
My trouble started this morning, I went to start the truck and RPM shot up to 3000-3100 with no "check engine" light. I cut the truck off and assumed it may have been stuck throttle cable - not it. Next I checked all visible vacuum hoses and all are on and in pretty decent shape. Next, I hopped on here and searched the forum I found suggestions to check TPS, MAF, and IAC circuits. I do not have a voltage tester handy, so I did the "disconnect" method to let the computer go to defaults. First thing I tried was the TPS, of course the check engine came on immediatly (so I know it's not burned out) and the RPM's only went to 1600-1700 when I did that and showed no signs of going any lower. If I try to put into gear, it slams into R and D, but RPM goes to normal range in those gears.

I have not tried to disconnect the MAF and IAC - honestly don't know where IAC is on this truck. Is the "disconnect" method an accurate way to diagnose without a voltmeter?

Any suggestions are greatly appreciated. Thanks all.

 

Not trying to bump this post so soon, but I found the problem and wanted anyone else with this problem to know what it was - for me anyways.

It was a vacuum line i missed - one that goes from the round black ball type of thing on the driver side attached to the hood. There was a vacuum hose that ran from it to the back of the engine that had a hole in it near the engine. I temporarily patched it until I can get to store to get new hose. Also had battery disconnected for about 15 mins while I worked on it to clear computer.

Everything back to normal - idle around 700 again!

 

whats that black ball under the hood used for? why is it there?

 

it is used as a reserve for vacuum

 

where does the line for the back of the motor hook up at? exactly. that is my problem. the line is off and i have no clue where it goes...any helop i need to know asap thanks

 

That depends on what you are driving...

 

the "black ball" is used to act as a reserve vaccum canister to prevent your blend doors for your heater box from closing to their default position when the engine is shut off. and as far as routing im not sure but i know its routed somewhere along the bulkhead (firewall)

 

On my 96 the line goes to the same port on the upper intake as the pcv valve. The port is located under my intake tube. The side sticking straight up is the pcv and the smaller is tied in to the three way below the vac reservoir.