BillR

I need some suggestions on what to look for.
I just had my motors (Merc 575SCi) rebuilt by Joey Griffin. All in all they run 150% GREAT. Start right up, idle well and run very well. The computers were sent to Mark in LA to get them to not be so rich and to raise the rev limiter to 5600.

I do have a minor problem though. It is mostly on one motor, although the other motor had the problem once. I know it is NOT a cut out switch (Alpha drive) issue.

Here is the problem:
While at idle, if I shift into reverse (sometimes forward) the motor will either stall or almost stall and drop to 300-400 rpm then surge up to 1100ish, and then settle down and run fine until maybe I shift again. When it does stall, it will re-start immediately. Also when flushing on the hose I try to run it @ 1400 rpm, but instead it will surge f/ 1200 to 1800 up/down, up/down and so on until I move the throttle.
This does not happen ALL the time. Only happens at the worse possible time. Vacuum is steady the whole time too.


What to look at? I was told that the 2 throttle bodies need to be bolted up "just so" and that one throttle plate my be sticking.
I was also told the computer learns how to adjust the IAC and needs time. Also was told the IAC may need adjusting.
If the computer does have to learn, it is not doing it very well as nothing has changed. Have been out twice.

I know someone has a clue - I just need to know what to look for. Nor do I really want to tow the boat back to Joey. Although I may have to. I am sure he can get it corrected.

GOODT

It does sound like an ICA issue the computer does have a learning cycle

in order to diagnos the problem the motor will need to be hooked up to a diagnostic computer to see what the ecm is doing

Linster

You need to hook up a scan tool orDiacom to the engine. I had the same problem last year. You need to make sure that the throttle position is at 0 or 1. The IAC needs to be aroung 30. If you were not careful when you put the motor back in maybe the throttle got advanced by accident. Mine did and after I got readjusted I had not more problems. The engine will see as little as 3 of a throttle position as trying to accelerate.

Wally

i cant say for sure on your setup...but one experience i had with a carbed motor i had was doing the same thing when shifted into drive.......drove me crazy....turned out to be a broken advance spring in the distributor!!! Its an easy check...