ZeRo2o9
Newbie
I have a 1990 5.7 tbi with 225k miles and it runs fine when accelerating but when I’m idling in park or sitting at a stoplight I get a random shake where voltage and rpm drops for a second and goes back to normal, it’s random it can happen once or a bunch of times on my way home from work. I was going through everything and did a tune up new ac delco plugs the cr43ts, wires cap & rotor from rock auto tune up kit united auto, new tps iac cts and pigtails for them, new ignition coil, tbi was rebuilt last year fuel pump was replaced almost 2 years ago, all parts were either ac delco or parts store brand if I couldn’t get it. I had a high idle issue at one point and found out the pigtail for iac was bad and I just went replacing old parts I thought were original. I literally have no idea what it could be I have some knowledge but I am not a mechanic and do not have the tools to read data from odb1. Is there anything that could cause what seems like a misfire at idle that I haven’t already replaced? My idle is smooth at looks like 600 rpm or maybe right on the bottom of the line for 600.