my 91 RS 5.0 5 speed started this round of problems by running hot .... i replaced the thermostat with a 160 deg. ...... then it started ideling rough a few days later and then power fell off .... I replaced plugs (bosh platnum) wires cap and rotor. ..... this was to no avail, power fell off even more over a short period of time, and the engine then wouldnt crank unless you gave it some throtle and would occationaly stall while truing to pull off from a stop. ...... i just cut the cat out and put in a pipe (no inspection in east Ga) and the power is back! with a vengence (yea i know its only a 305 TBI) one side note that may be important is there is a sensor that has evadently melted in half on the right head about mid way back of the engine (im assuming that is the fan switch since that dosnt work and i cool the engine with the A/C turning it on). the engine still idles a lil rough i have disconnected the battery to reset the computer and am hoping all is cool ... if not any ideas of what and where i need to look next? David

oops i almost forgot .. the only code im getting is for the EGR Valve ..... that i have been getting for about 2 years and have just been to lazy to replace. David

 

Squatch,

If you're using stock ECM progrmming and 160°F thermostat, you may not be achieving full closed-loop operation. The CTS has to get to 176°F or higher to fully enable the EGR, hot idle parameters, etc. You might want to reprogram or change to a 180°F unit.

 

On top of what Vader mentioned I would get those Bosch Platinums out and put some good old AC delco plugs in. I know alot of people have had running problems with those Bsoch plugs in these of engines, the TPI and the TBI's.