Changed to the BBC injectors?
New to the site in need of help! My (1987) truck originally had a 350 TBI in it that blew up on me. I figured if I was going to go to the extent of rebuilding a motor I should "GO BIG OR GO HOME" Right?? Yeah...... So I pulled a 454 out of a 1988 Chevy 1 ton. Took it to a reputable machine shop and told him I wanted him to build it from oil pan to intake.. I now have it all bolted in my truck and changed the computer over to the bbc one. Everything is new on the motor including dist, sensors, plugs, and wires, etc... I recently found out from my GM dealer that from 1988 to 1990 the BBC tbi did not come with a escm but the 350 did so I changed the harness to the 1988 bbc one. We ran the motor with the 350 harness and the escm until I found this out. The motor has been backfiring through the tbi and seems to not have the power I think it should. I had fowled 3 plugs which showed up on the scope. We replaced the plugs with the next hotter plug and it seemed to run better but not the best. It seems to be running rich when it's cold and lean when hot. We've replaced the cts 3 times and checked all readings. Changed the computer to a different bbc one. Same thing. It has a backfire when under load and to me seems to have a slight miss when at or just above idle. No codes.. We have almost 40 man hours in this and still have the same issue. It has 2 new GM fuel pumps in it with a new diverter valve, new filter and new regulator kit in tbi. I'm so lost and frustrated being in this $4000 for the new motor and having problems.. This will not be smog legal and has no smog on it. I did a compression test and all were between 138 and 145 psi. Any and all help is very helpful.
Changed to the BBC injectors?
Yep. It's the BBC tbi has edelbrock intake for tbi. Worried we may have fried the module in the dist or?? IDK
Thanks for the help!
What a pain this has turned into
Any ideas anyone has?? I'm open to any thoughts or questions.. We've done a lot of checking just not sure what the deal is. What would make it backfire under a load only?? At idle when cold it runs real rough and if you bring it above an idle it will run like it has a BIG cam in it or like flooding out intermitenly.
First, Check the timing. Second, if it is fouling plugs, it is probably running pig rich. There are 2 temperature sensors on TBI, which one are you changing? Also I recommend getting an ALDL cable and datalogging your engine, it will help everyone diagnose your problem.
Been replacing the one on the front of the intake... Where's the other at?? I know what you mean.. Would just most dealers have one or is it something another shop might have. Not familiar with the aldl but it sounds like something that would be nice just to have to see what's going on. I fired it up this morning and yeah it's running rich when cold. The sprays look good and if it warms up it runs better. You can have it in park, bring the idle up to about 1200 or so and you can hear it not smooth. You can rap the in park and it's awesome but you go to drive it and it seems like it has no power and rolling into the gas it backfires through the tbi. It's only under load that it backfires but to me it has a slight miss at idle and you can hear it better just above an idle.
O and timing seems ok.