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454 XL TBI stalling

n36511

n36511

Regular Contributor
helping a friend troubleshoot his engine woes (blind leading the blind). He was having an issue with his 454xl TBI stumbling under a slight load. A mechanic recommend that his TBI needed to be rebuild. The mechanic rebuilt the TB replacing the injectors, IAC, and one other electronic part that I cant remember what it is named. The engine fires up great and as long as you keep throttle to it, it sounds good. Let the throttle go to idle and within 15 seconds it dies. Cranks right back up with no issues only to die if you leave it at idle. If you try and pump the throttle a little at idle it sometimes backfires thru the carbs. No noticeable vacuum leaks and the fuel pump is only a year old. Any thoughts as to where to go from here? Also, we are not sure if the mechanic used crusader injectors and stuff for the rebuild or just standard chevy parts. Would that make any difference?

Thanks for the help
Scott
 
Not knowing the year of engine, we would only guess. I have two '97 454XLi's. Assuming it’s in the same year as mine, I would be looking at timing. Check distributor timing, the computer and its connections in the distributor. Does it have a "Check engine light"? Might be good to call around to a marine shop to see if they have a computer to hook it to. It might just pin point the problem quickly.
 
Is he positive the IAC was replaced? Also, he must ensure the battery is in top condition and that all battery cable connections at battery and engine are tight and corrosion free. Check engine harness plug also. He may also want to disconnect the fuel line at the pump to isolate the engine from the vessel's fuel tank and hook up a portable tank. Be carefull, shut off fuel valves. Run the engine. If the problem goes away, the issue is not the engine but anywhere from the engine to the fuel in the vessel's tank. If the problem persists, you've eliminated the fuel supply as a possible source of the problem.
 
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