02 IQ 48v top speed only 13 mph

zookie2002

My cart runs slower than it used to, and I'm wanting to get it back to speed code 4 performance. It used to run 19-20 mph, and now tops out at 12-13 mph. This change happened overnight about 4 months ago after a particularly long balancing charge on the old battery pack (16 hours). Old pack held 78% SOC, and one had a small crack (leaky) along the seam of the case - so they were due for replacement. New batteries installed yesterday, and this morning was the first run.

The performance of the cart with new batteries is identical to the old batteries. So frustrating!

The torque feels weak, meaning it accelerates smoothly but gently. It reaches 12-13 mph in about 250 feet, and fluctuates between 11-13 mph while running on flat pavement according to my GPS app. It cruises at lower speeds smoothly.

I pushed the cart around the yard to wash the battery compartment before installing the new pack, and it did not feel like the brakes were engaged. Tires are stock size, 25 psi, and alignment is good.

Cart details:
2002 DS IQ 48v, GE motor, curtis controller (black). Standard wheels and tires. Brand new Crown 165 pack (date code A19) is just starting break-in, and read 50.7 volts after 12 hours rest. Solenoid was replaced March 2018.
MCOR was upgraded to MCOR4 in April 2018.

Do the current symptoms point to anything obvious?

BGW

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NoleFan4Ever

Sounds like a speed sensor failure. Manually push the cart forwards and backwards and see if you feel resistance and hear the beeping occur.

zookie2002

Thanks for the advice. Pushing forward and backward, the resistance is felt after 2 feet and there is beeping.

Could it be possible that the OBC reset and forgot the speed code 4? I still have the factory sticker with the code.

NoleFan4Ever

Your OBC is your On Board Computer and only controls the charger. The Curtis Controller in your cart is a logic controller and it contains the speed code. No way for it to really "forget or reset", but you could still be in Limp mode if it sees a welded main contactor (solenoid) or a few other things. Limp mode will put you at half speed, but an MCOR issue can do what you describe also.

With the key off, pump the pedal 25-30 times to the floor and then see if it runs any different.

TahoeDawgZ71

Probably worn pedal linkage. How far (in inches) do you have to press the accelerator before you hear the solenoid click?

zookie2002

I tried the pedal pumping 30 times to no avail. I also tried the paper clip test to bypass the micro switch, and that made no difference.

Then I disconnected the speed sensor, and the cart couldn’t do better than 8 mph (which is slower than usual). So I plugged it back in and I’m back up to 11 mph. Next I removed the speed sensor from the motor, and found the magnet to be in great condition. Then reinstalled the speed sensor and tested it by piercing the insulation on red and green wires, and the voltage fluctuated 9v to 14.5v as I manually rotated the hub. So the speed sensor seems okay.

Last effort was to measure the pedal distance using a carpenter square. At rest it is 6.5” from the wall. At 3 1/4” the micro switch clicks then solenoid clicks at 3” to the wall. So I have 3” of distance for acceleration. As a side note, I upgraded to the MCOR 4 middle of last year, and the linkage tolerance seemed tight. Is the 3” is too short?

Could my MCOR4 (China made) have developed a dead zone after just a few months of use?

NoleFan4Ever

Here is how you measure the throttle output to the controller. With the batteries connected, Tow/Run switch in Run; place the black (–) probe on packs main Negative post and the red (+) probe on the yellow wire at the 3-pin connector near the MCOR. (The reading should be approximately ~0.32vdc to ~0.5vdc with the pedal up). Slowly press the Go Pedal and the readings should increase until it reaches ~4.65vdc or more when the pedal is fully pressed. (Anything less than 4.60vdc and you are not reaching full throttle). If the reading is erratic or jumps all over the place it is a bad MCOR output signal..... Get a genuine OEM here https://www.revolutiongolfcars.com/mcors

TahoeDawgZ71

Absolutely. The Chinese MCORs have well-known issues and are often bad right out of the box. A few years ago I attempted to sell them. I bought 10 and had 8 of them fail within 6 months. 2 of them quit operating completely and the other 6 failed to achieve max throttle output. With the pedal on the floor they only put out about 70% throttle. These were installed on Precedents so there were no linkage issues to worry about. Check the output as NoleFan described and if it has failed, replace it with an OEM unit.

EDIT: Be sure to remove the MCOR from the car before you do your testing. Use the vehicle drive bar to manually turn the MCOR by hand. This will tell you for sure whether it's an actual MCOR problem or a linkage issue. Your linkage sounds worn to me. You should get a click within the first inch or so of pedal travel.

zookie2002

Thank you TahoeDawg and NoleFan. I found the issue using your suggestions!

I was able to determine the pedals have worn linkage that created a gap of 1/16". A temporary shim got the cart back back to 19 mph, and solenoid now clicks after 1.5" of pedal travel. I found posts where BGW members are using fuel hose or zip ties to solve the issue, so I'll try that as a more lasting repair.

TahoeDawgZ71