hi, im new to the site. i have a 91 k5 that had a tbi small block, i swithed it to a 90 454 from a r2500 suburban. i added headers, open element air cleaner, and wired in a heated bousch o2 sensor. the issue is it starts up and runs good for about 30 seconds, then the idle drops down and it starts backfiring out the exhaust (both sides) and it acts like it has a bad accelerator pump when you rev it up, like a severe hesatation and then it takes off like a bat out of hell. i also got rid of the lines that bring coolant to the adapter plate. base ign timing is 8 degrees btdc. also tried a new tps which did not help. any input would be greatly appreciated. thank you.
CK5
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91 k5 454 tbi issues
- Thread starter jbxc600
- Start date
Sounds like your timing is way off. Im not sure what the 454 should be set at but the 350 on a tbi setup should be 0 degrees. You could try unhooking the tan and black wire at the firewall then start it up and reset your timing, then reconnect the wire and see how it goes.
Not sure if you know this but the 454 tbi uses a different fuel pump with higher pressure in some years. You may need to change it to the suburban pump.
Also I am pretty sure it should be at 8 degrees btdc so you have that right. Sounds like a fuel issue to me and that would explain the throttle tip in issue.
Also I am pretty sure it should be at 8 degrees btdc so you have that right. Sounds like a fuel issue to me and that would explain the throttle tip in issue.
I looking it up they should be the same pressure (sucks not working at the dealership anymore where I can look in a manual). I would still check the pressure and change the filter if you haven't. Lean will make it run like it does.
Jester1
1/2 ton status
Just a thought didn't see anything about a swap on the ECM. Don't the 454's need the ECM swapped because of the spark advance for the tbi? Something in the programing for the Big Block.
I wouldn't mind some insite myself wether I am on right track or completely wrong. Still learning myself on TBI, EFI. Guess it's time to get out of the carb age.
I wouldn't mind some insite myself wether I am on right track or completely wrong. Still learning myself on TBI, EFI. Guess it's time to get out of the carb age.
I do have the computer from the 454 burb, also i have turned up the fuel pressure a little not sure wat it is runing for psi still working at geting a gauge to hook up some how cuz i re bent a fuel line and my adapter for the gauge wont fit anymore.
