searls84
Member
- 195
- 6
- 18
- Location
- Las Cruces, NM
This one has me stumped!
The issue I'm having is that the motor won't return to idle correctly, almost like it's starving for fuel. When I let off the gas suddenly, whether shifting gears or just a simple rev of the motor, the RPMs will fall below the idle set point. It sometimes recovers and attempts to stabilize at 750-800 RPM and sometimes it continues to fall and kill the engine. When the motor is cold the issue is least noticeable, the RPMs will still fall below but only by about 100-200 RPM and then semi stabilize at around 750 RPM. When it's at operating temp it's the worst. The strange part is that the severity is not consistent. Some days it will die between every shift of the gears and other days it will only "stumble" between shifts. Also, when I let the motor cool at idle down after driving, it will "hunt" for idle.
Here's the back story...
I decided to a motor swap in my M35a2c over the Christmas holiday with a newer production and lower mileage Thick Deck motor out of my M109 parts truck. The "new" motor, an LDT465-1D with a non G code IP, had been sitting in the truck for around 5 years. I got it started in the parts truck and it ran fine as best as I could tell from the 45 seconds I let it run. Before I pulled it and stuck it in my deuce I went over it and did a bunch of maintenance and upgrades to it while it was easily accessible. Here's what I did before the install.
-All new "plastic" and rubber fuel lines
-Bypassed FDC
-Flame heater deleted
-New Hydraulic Head Orings
-Spin on fuel and oil filter adapters with filters
-New air filter
-All new temp & pressure sending units
-Oil change
-New oil pan gasket
-New air compressor
-New water pump
-New belts
-New clutch/pressure plate/throw out bearing
-Added C turbo
So here is what I've done since the install to try and fix this issue.
- I dumped a gallon of Seafoam in the tank and ran it hard for about 60 miles. No change.
-Checked the fuel shut off rod for proper function. No problem found with it.
-Adjusted fuel rate on FDC up and down. No change.
-Adjusted Idle screw up to 950 RPM. Seemed to improve at higher set idle but was still not right.
-Valves adjusted (.12 intake and .25 exhaust)
-New (not a takeout) Hydraulic Head installed. No change
- Checked all fuel lines and filters. No leaks or pinched/crushed lines.
-Checked intank pump for operation. Works.
I've put about 200 miles on it with no improvement. Going down the road it runs excellent and has lots of power. So where do I go from here? I've gone through every thread I could find that seemed similar to this issue and tried the remedies and recommendations to no avail. Right now I'm leaning towards there being an issue with the droop screw adjustment being off. Thoughts on that?
Any help, advice, threads to read, or anything else would be appreciated!!
The issue I'm having is that the motor won't return to idle correctly, almost like it's starving for fuel. When I let off the gas suddenly, whether shifting gears or just a simple rev of the motor, the RPMs will fall below the idle set point. It sometimes recovers and attempts to stabilize at 750-800 RPM and sometimes it continues to fall and kill the engine. When the motor is cold the issue is least noticeable, the RPMs will still fall below but only by about 100-200 RPM and then semi stabilize at around 750 RPM. When it's at operating temp it's the worst. The strange part is that the severity is not consistent. Some days it will die between every shift of the gears and other days it will only "stumble" between shifts. Also, when I let the motor cool at idle down after driving, it will "hunt" for idle.
Here's the back story...
I decided to a motor swap in my M35a2c over the Christmas holiday with a newer production and lower mileage Thick Deck motor out of my M109 parts truck. The "new" motor, an LDT465-1D with a non G code IP, had been sitting in the truck for around 5 years. I got it started in the parts truck and it ran fine as best as I could tell from the 45 seconds I let it run. Before I pulled it and stuck it in my deuce I went over it and did a bunch of maintenance and upgrades to it while it was easily accessible. Here's what I did before the install.
-All new "plastic" and rubber fuel lines
-Bypassed FDC
-Flame heater deleted
-New Hydraulic Head Orings
-Spin on fuel and oil filter adapters with filters
-New air filter
-All new temp & pressure sending units
-Oil change
-New oil pan gasket
-New air compressor
-New water pump
-New belts
-New clutch/pressure plate/throw out bearing
-Added C turbo
So here is what I've done since the install to try and fix this issue.
- I dumped a gallon of Seafoam in the tank and ran it hard for about 60 miles. No change.
-Checked the fuel shut off rod for proper function. No problem found with it.
-Adjusted fuel rate on FDC up and down. No change.
-Adjusted Idle screw up to 950 RPM. Seemed to improve at higher set idle but was still not right.
-Valves adjusted (.12 intake and .25 exhaust)
-New (not a takeout) Hydraulic Head installed. No change
- Checked all fuel lines and filters. No leaks or pinched/crushed lines.
-Checked intank pump for operation. Works.
I've put about 200 miles on it with no improvement. Going down the road it runs excellent and has lots of power. So where do I go from here? I've gone through every thread I could find that seemed similar to this issue and tried the remedies and recommendations to no avail. Right now I'm leaning towards there being an issue with the droop screw adjustment being off. Thoughts on that?
Any help, advice, threads to read, or anything else would be appreciated!!
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