I have two 502EFI's with plenty of mods. I've had them for almost 7 yrs and they've been great. Just overhauled both completely and bored .030. Fast forward...... In the boat, both started quickly. One motor at idle surges up and down for a while.

Any suggestions where to look first ? These are 1996 VST models.

Rebuilds were very thorough. Top to bottom.

Thanks

deboatmon

Do they have blowers? Surge on a carbed engine is usually caused by a bad air fuel adjustment. I am assuming it would be about the same on EFI, just maybe a clogged injector, or crossed wire. Clogged air cleaner.

Just a guess. Not really a lot of info for us to work with.

No blowers? Then maybe a rocker out of adjustment. Still could be a computer issue.

Bad IAC?

went through the same thing. found out it was the timing was out.....(too far advanced by 5 degrees). make sure you get a computer and put it in timing mode and check it again with a light.

Sometimes the TPS goes bad. Any alarm codes? If not I would look at fuel supply.

Either timing or tight throttle throttle cables.

I had same problem, turned out to be the throttle cable was not coming all the way down to idle. Unhook the throttle cable and see if it still does the recycling. Then you know the throttle is completely closed. Minor adjustment to fix if this is it.