the427chevy

anybody got any secrets or tricks for making these TBI units work the way they did new? i have a 87tbi 350; it has new GM (right from the dealer) TPS and iac valves, and yet it still likes to stick on high idle, about 1000 rpms, 850 when its in gear, and some days it will drop right down to an 800rpm idle, and it eats through the gas more than it used to

mudmaniac

Does the check engine light come on? It could be an issue with a temp sensor if so.

maxxman04

have you checked for vacuum or intake leak? SOMETIMES high idle could be caused by vacuum leak. only takes that one vacuum line that's hidden to do it.
as far as performance, power chip for ecm, throttle body spacer, cold air intake, quality cap/rotor/plugs/wires. better than stock coil. these are a few basic, easy bolt on upgrades.

the427chevy

i haven't checked for vacuum leaks, as the truck has minimal vacuum lines, just EGR, MAP and the vent line from the canister, as for coil, its an MSD, i have MSD distributor, accel 8.5mm wires, throttle body spacer, and i'll mention again that its not always having a high idle condition, and i was making poor (8-9) mpg, when i swapped to the heated 02 sensor it pushed me up to about 11, when i first bought the truck with my 35's and 4.88 gears i was making almost 16
im going to dig out the carburator cleaner and check the TB and intake gaskets in the morning; i have an edelbrock aluminum intake to install but i've been waiting on my cam to put it all together, this may the oppertune moment to get permission from the wife to stick er in

the427chevy

and ftr i have no DTC's

maxxman04

only takes one line to cause. check throttle body mount gaskets as well. IAC valve, def check egr. sounds like you're looking in the right areas. if you have, or can get one, a vacuum gauge, check how much vacuum.

the427chevy

blah blah blah found an exhaust leak under the EGR valve, fixed that, no changes, no vacuum leaks on the intake, but replaced the TBI gasket when i converted to the Round style TPS sensor plug (much smoother throttle response); stacked up a second TB spacer was still having a high idle condition so i had ordered a new set of valve covers, installed them with a chrome round style pcv breather and capped off the line on the throttle body and wambo, perfect idle.