IH-454 Gas High Idle

Hopefully, this post finds itself in the proper forum area:

This year, my tractor (IH-454 with C-157 engine) will not stay running at high idle or PTO speed. After operating for a few minutes it will randomly lug way down and die but if I am quick, I can shut off the PTO and idle down for a few seconds then slowly bring everything back up. Or, I can idle less than 1000rpm the engine will appear to run just fine indefinately. If the engine dies, I can shut off PTO and close governor control and tractor starts right up.

I originally thought I had bad gas and completely drained the system. Then, I thought it was fuel pump not providing enough fuel, but fuel flow appears to be adequate, even with a small tear in the top gasket/diaphram. While troubleshooting and observing, the governor appeared to be sticking but after complete disassembly, cleaning,checking linkage, and manipulating running governor controls, I am back to something wrong with the zenith model carb. A quick disassemble and cleaning did not reveal anything obvious.

CARB: Ever since I bought the tractor, the choke has always been in the center position and ran fine. I did verify proper operation but thought "If it ain't broke....don't fix it". Yesterday, while making idle ajustments, to my surprise turning the to mix screw did almost nothing.

Any ideas or recommendations are very welcome.

I would pull the main jet and make sure it is clear. Sounds like it's not getting enough fuel.

Thanks. I will definately look into your idea again just in case. With the choke position that seems to make sense.

I did tear the carb apart again earlier this morning (before getting your advice) and nothing caught my eye. Maybe it was re-jetted incorrectly by previous owner as there is no tag or ID on the carb, other than Zenith name. I swagged all the ports and blew them out with cleaner/air....again, nothing caught my eye.

After swapping out the plugs just about an hour ago (which were in questionable shape) the tractor immedietly seems more responsive, even regarding the choke position. However, after a few minutes of mowing, the engine now surges wide but regularly on 2 second intervals. The other ignition parts are so new they aren't even dirty yet, including the points.

The coil isn't getting hot, per other forum posts.

next time it does that loosen the gas cap. tank vent could be clogged.

After working with this tractor for a few weeks now, I went back to the local dealer with the carb. The service manager tried to help but told me the carb was not the correct one and that I should have a Marvel, which is odd because the Zenith is clearly shown as an option in the service manual.

After giving up for a while and shopping around for a sub-compact diesel replacement, I checked out the 454 again yesterday. On a whim, I tried and was able to run the engine at high idle with the PTO engaged with a gasoline "IV drip" to one of the carb's other inlet ports, even though the pump appeared to be working. Whenever I choked off the IV drip the engine would appear to starve for fuel but would rev back up when I raised the IV again. I also noticed the ignition coil is now getting so hot that I had to hold it with a wrapped up towel. The coil is making a sloshing noise which I have never experienced with a coil.

So.....gonna try a new fuel pump and coil and share the results so it can help others.

I bought a fuel pump thru Ebay store as I didn't feel like paying $130 at the IH dealership. I ended up getting the wrong pump and lack of sources lead me back to the dealership. The good news is that the tractor ran fine under load. There is a little amount of adjustment left to eliminate surging.