Medical Issues force me to sell...and I need help!

[BioRobotic]

I have a 1995 Chevy K3500 with 454 cid engine that just won't run right. I have replaced Fuel Pump and filter, TBIs, Fuel pressure regulator, MAP, MAF, TP. O2, Knock,and heat sensors...I have replaced the EGR valve, timing chain and gear, distributor, wires and plugs, computer...even knocked out the catalytic converter because some genius told me that was the problem since I got rid of everything else...I need some ideas to look into. The engine idles a little high but ok IF the MAP sensor is disconnected...after 5 minutes in gear if I am lucky, the engine starts coughin, sputterin and spitten threatening to quit. If I stop the engine, wait a few seconds it will get me about 500 yards down the road and starts all over again. No mechanic I have taken it to has figured it out. Please advise
Robert

 

[NVW]

Welcome to TTS, sorry you're in your predicament.

Having changed about everything leaves me to believe it has to be the computer or wiring.

 

[littleboy]

We had one that acted similar. After much head banging we finally found the problem. One of the ground straps for the engine or the computer had corroded. On the passenger side of the engine bay down on the frame rail is a couple grounds. Check them and make sure they are good. We made 2 new grounds and went right from the battery to the frame and to the engine.

 

[WarWagon]

High idle is too much air from a vacuum leak or possibly someone has turned up the TBI adjustment screw to open the throttle blades too much.

Have you removed and cleaned all the passages in the TBI unit? Major vac leaks from: intake manifold gaskets, leaking brake booster, vac lines, TBI gasket, PCV valve/hoses.

Brake Booster test without driving as you will not have power assist on the brakes: Pinch the brake booster line off and do not drive it to see if idle improves. If it does you have a leak from the booster.

Is the TBI worn out? As in groves where the throttle plates are, Shaft tight?

Is the Idle Air Controller motor working? Removed, cleaned and tested? You need to go over 45 MPH for the computer to issue 255 steps closed to learn the IAC position.

How old is the fuel and have you checked it for water in the tank when it was out?

 

[someotherguy]

Disconnecting the MAP sensor is going to cause you more problems than it solves, because with the low vacuum signal created this way you're going to overfuel badly.

From your description it sounds like the issues you're having are while you're attempting to drive it with the MAP sensor is disconnected? What happens while it IS connected?

You said you replaced a "heat" sensor - what sensor do you mean, specifically? Do you mean the coolant temperature sensor (CTS) - which is on the front of the intake just ahead of the thermostat housing? If so, please post the part # of the sensor you installed, to be sure you got the right one.

What littleboy mentioned on the grounds is very important - if the sensor network doesn't have good grounds, it's going to run poorly. Particularly, the coolant temperature sensor which depends on a resistance reading, if the grounds are poor, it will report a much colder than actual temperature, causing a rich fuel mixture.

Richard