Engine Knocks at 2500 RPM Regardless of Load

[axisT6]

I will give specifics first. The truck is a 1995 ECSB half ton with a TBI 305. It has the ultimate TBI mods, a mild tune, and has been converted to a manual trans. When I did the tranny conversion I also burned a chip so the ECM (16197427) would not longer look for an auto. I basically put it in "manual tranny" mode.

All was well until one day I noticed the engine was knocking. It knocks only at 2500 RPM in all gears. Also, I can't rev past 3500RPM and the truck is throwing auto trans codes. Base timing was off half to one degree, but I don't think this is a cause for the symptoms I am experiencing.

A friend of mine experienced something similar and said that his distributor was shot. He said that he was getting error codes that had nothing to do with the ignition system as well. My cap, rotor, plugs, wires, and coil are a few years old, however my distributor is original ( i know i know). The truck has 370,000 miles on the original engine and has run great till now. Since the knock is RPM specific, I am thinking it may be the module under the distributor which, if it is, I will just replace the whole thing.

What do you all think?

 

[SouthBoston]

Replace the distributor, then go from there

 

[axisT6]

I really hope that is it. I only need this thing to keep it together a little longer as I have a mean 406 SBC waiting to go in.

 

[benjaminbarton55]

I replaced my distibutor with these exact symptons. That seemed to fix it. The distributors are known for the gears wearing out. However when the truck is under load, I dont got much power. I dont know what the problem is.

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[axisT6]

Nice to know. Thanks!

 

[Crash]

If it's just the gear can't you just replace the gear? My truck does it too only at any rpm under any load, I wonder if that's all I need too.

 

[axisT6]

I am sure you could just replace the gear, however I have the ORIGINAL dizzy in mine. I got around to picking up a new complete assembly yesterday. Gonna try to get it in this weekend or next. Time has not been on my side.

 

[axisT6]

Well, it looks like I have a gasket issue on the intake or the head. The engine is now pouring coolant. I am just going to move forward with the 406 install. Thanks for your help everyone.

 

[axisT6]

I was under the truck and noticed that one of the larger solenoid wire going to the starter is pretty bad shape. Apparenty it and the knock sensor wire both had bare spots that were touching. I separated and insulated these wires and the knock went away. I still hit a wall at 3500 RPM, but that is because I didn't clear the error codes I think. To cover my bases, cleared the codes (disconnected and reconnected ECM), and I examined the tune and disabled pretty much everything in the .bin file that had to do with an auto trans. All is well now.