VetteLT193

Does it die instantly when going into gear or does it struggle at all then die? You can safely bump the RPM as a test. carefully bump it to 800-900 RPM and see if it does the same thing.

IAC or possibly a vacuum leak are the obvious culprits.

4mulafastech

No problem! For some reason I was really paying attention to where my 6.2 MPI's were idling. Over the winter I changed spark plugs and put in fresh IAC filters in the throttle bodies. The old ones were pretty dirty.

This was running on the hose with no props installed. What's interesting is I put them in gear, both forward and reverse, and for a brief moment during shifting the engines they would drop to 500 rpm then go back to 600 rpm (according to the SC5000 digital tach). Engines sound and run perfect and no sign of dying during the shift. I even saw it drop to 450 rpm once. The cam in these engines is sooo mild. Just another observation.

nova26

Update: I've been traveling with the MTI BatBoat attending the OPA races and haven't had much time to spend with the P-29. So this is where I'm at with it, did find the props were out of time, fixed that still dying. We put new IACs both motors cleaned the throttle bodies still dies. I've run about 300gal threw it everything is great but dying when put into gear. Someone mentioned to me that the motors are tired, but it was fine before we pulled them. They don't smoke don't use oil the oil is still clean. Fires right up and sounds strong. Motors have around 440hrs. It still runs 74mph with two guys cooler 1/4 tank and all the other junk in the boat. 76.6mph is what Power Boat Mag ran it in 1996. I'm trying to find my water ears now to try in on the trailer.

Powerquest230

Simple Blower Surge..

Griff

Great advice if he had blowers

Got Cigs

I had 22 Donzi Blackhawk edition with the 502EFI doing the same thing. Turned out had to reset the timing.

Powerquest230

Actually my point of jest was to add Blowers and then shift during the "up surge". Sometimes laughter isn't the best medicine..

Not familiar with the MPI engines but do they have a distributor? If so could the advance plate/springs be broken and the bump of going into gear wacks out the timing killing the motor? Used to have an older chevy engine that would run perfect other than the occasional stall or backfire (which was bad enough to blow off all vacuum lines) and after many hours found a broken piece on the advance mechanism.

Griff

Yes they have distributors. They do not have any type of springs in them. The advance is all electronic and in the module.

off roading

A friend of mine has a p29 with the same problem the iacs work fine and the timing is correct still wont shift right

nova26

I put water ears on the trailer today and gave them both a try. When you put both of them in gear there is NO rise in RPM. They both drop about 20RPM then back to 600RPM, there's no way you will kill it on the trailer.