90 454 TBI hesitation and boggs

Hey everyone! Im going nuts!! My 90 Chevy c3500 with a 454 TBI is hesitating and feels and sounds like a slight misfire. It is gradually getting worst and worst. Ive changed the fuel pump (factory replacement) filter, plugs, wires, rotor, cap, map sensor, air filter, and changed the oil. I dont know what to do!!! Also the timing is dead on and its shooting no trouble codes!! Ive checked the egr diaphram and it moves, not stuck. PLEASE help me. THANK YOU IN ADVANCE!

A misfire can be caused by intermitent spark. My wife owned a 90 subur 350 TBI it had intermit mis fire so bad flames would shoot from TB when open. I had veh at my mech at time he had change ign mod etc no change he call GM and they told him change coil in dist. I being a electrnic tech suggested brain, he and GM stated they dont go bad. He was never able to fix I got a brain from van with same eng( obd I so much easier) anyway it was brain!!! try coil first if you want but if you have changed all other spark related parts try brain.

Thanks for the reply. I went out last night and started it up and I did see some flash from the wires, so Im going pick some up today and see if thats it. I had the heads rebuilt back in Oct/Nov and maybe the mechanic was a little too rough with the wires. Thanks again for the input, if the wires arent it I will try the ECU. Were you getting any trouble codes on your wifes Suburban? Cause Im not getting any.

In your op you said you changed plugs , wires , rotor, cap etc. So you are throwing me off track but as I said spark problems can cause misfire. its smart to look at it in the dark and since you see arc's on wires you probibly have the problem under control nice work let me know. But before you change brain look at all else. The brain gets cold solder joints and is fairly cheap if you need to replace most auto stores carry. good luck, oh and no my wifes veh did not code yours like hers obd I so not as smart as obd II.

WOO HOO!! :grinyes: I changed the wires, plugs and cap and the truck runs wonderful! The plugs were all fouled. The only thing I can think of is that I ran some injector cleaner through and I think I made it a little too rich and not enough fuel, so it damaged my plugs. And the wires were already bad. Thanks again!

I think your wires caused spark plug problem but you got it when you check in dark and saw the sparks from wires, glad it worked out thanks for posting back.