5.7l EFI Mercruiser TBI Bravo surging idle stalls

[b0horman]

I have a 2000 5.7l EFI TBI Mercruiser with bravo 3 Stern drive, that surges at idle in neutral only after engine has warmed up. It will surge or stall / die when you put it in gear if you don't give it any throttle at first. anything outside idle it runs great, trolling and at high speeds no issues. At first startup in cold it will idle and purr like a kitten. After it warms up in neutral it will almost die then it will surge up to 2,000 rpms back down to normal idle, 650 RPM, then almost die surge back up then back to normal idle then it will completely quit. I have replace the idle air controller IAC and the throttle position sensor TPS. I have all new plugs and wires. Replaced the injectors. No codes with scan tool. This doesn't occur if I disconnect the temp sending unit. Is something going on with ECM or computer? Any suggestions on what I could check. Can the ECM be reprogrammed or checked to see if that's the problem?
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[Fun Times]

This doesn't occur if I disconnect the temp sending unit. Is something going on with ECM or computer? Any suggestions on what I could check. Can the ECM be reprogrammed or checked to see if that's the problem?
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First thought would be an failing out of range temperature sending unit affecting the fuel parameters of the ECM as the temperature sender is one of a few senders that control fuel calculations the ECM read.

MAP and Intake air temp sensors do too should your enine have the Intake sensor as some do and some didn't to your engine model.

Next up to the list to consider could may be a just a bit lower fuel psi than normal and with disconnecting the Temp sending unit helps tell the ECM all is okay again as it added more fuel....As another quick test, Try disconnecting the vacuum line hose going to the fuel regulator as that generally helps add fuel psi which may help add to the theory.

Throttle Body & Butterfly Plate and flame arrestor are all wiped down clean?