my t/a has a 93 caprice c91 motor with the TBI unit , the ecm is out of a g10 van i believe 5.7TBI ok my problem is that my idle out of no where will suddenly jump to 1000rpm and stay i have to shut off the car and depress the gas pedal a few times and then its normal again , i replaced the TPS , Coolant temp , and cleaned the TBI unit multiple times , it does it randomly some days it doesnt do it at all others quite often plz help!

 

first check for any codes.
if it has codes, clear them & see if they come back, if they do, repair them.

if you don't have any codes or they didn't come back, your going to need to do some data logging to see whats going on.
if you have a laptop, you can buy or build a cable, get TunerPro & the right definition files for your ECM & mask & record some logs until it acts up. then go through the log to see if its something the ECM is doing.

 

ecm had its day replaced with a salvage unit no issues anymore