KOHLER 26 EFI O2 sensor fouling

[Jet Mech]

Has anyone had a similar problem? I don't know if I can credit it to fuel addatives locally or what? I have had to clean carbon deposits off of my O2 sensor after only 15 hrs. from previous cleaning. (Engine has 260 hrs. on it total.) Engine R.P.M.'s will start to drop off from 3750, with blades ingaged, and not recover as they would with fresh plugs and clear O2 sensor. If I don't throttle down and imediatly bring the engine R.P.M. back up to full power with the blades disengaged, the engine seems to go to a "full rich" condition and foul both spark plugs and in time the O2 sensor. Other than this occasional condition, the mower runs like a scalded dog. Any help would be appreciated. :headscra:

[Lawn Tek]

Yep , been there done , that , Kohler has an up date ground kit for the bolt on the starter . And snap connections in the wiring harness should be unplugged and lubed with dieelectric grease , then zip tie them tight together . Last time mine did it there was a hair line crack in/the muffler , muffler was replaced ,and that fixed it

[nardharv]

I have the same issue. It acts as if the fuel system is not able to increase fueling with increased load demand.

Lawn Tek - What does the starter ground kit intail? Did this fix your issue?

Jet Mech - Have you found a solution to your issue?

[Jet Mech]

nardharv,

I have found by physically cleaning the carbon deposits off the O2 sensor "fins" with spray solvent & parts cleaning brush helps greatly. (I have even gone as far as using Grease Lightning brand spray cleaner rinsing off with water and blowing dry with compressed air. This method works rather well, believe it or not.) :laugh:
After re-installing the cleaned O2 sensor, I have taken a new approach to my starting up the motor. Upon start up, I go to 3/4 to almost full throttle (3500 R.P.M.) immediatly for approx. one minute. After the initial warm up of one minute, I find that the Engine Control Unit and the O2 sensor are in sink, (that being the O2 sensor is "HOT" enough and the Engine Control Unit has stabilized and not in a "Full Rich" condition.) In the past I found that if the motor was not taxed enough at start up, the O2 sensor would work as it was supposed to and give an input to the Engine Control Unit to go "Full Rich" condition, thus, fouling the O2 sensor & causing more problems/loss of power.
I have had no need to replace my factory installed O2 sensor since I have used the above cleaning/start-up method. It's been over 250 hrs. since I last had to clean the O2 sensor. The initial fouling of my O2 sensor probably occurred with only 150 hrs. on the engine.
Hope this gives you some ideas that might work for your motor. Good Luck!

[nardharv]

Thanks for the info! I pulled a plug last night and sure enough it looks like the engine has been running extremely rich... I can imagine the O2 sensor is looking pretty bad. I attempted to pull it out but couldn't. I gave it a good shot with penetrating oil. Hopefully I will be able to get it out tonight to clean it.

Thanks again.

[nardharv]

I was able to fix the issue this weekend. Here's the story...

I down loaded the service manual off the Kohler website. Thank you to Kohler for actually having the a service manual available. I went through their O2 sensor diagnostic steps and wrongfully concluded I had a bad O2 sensor. After checking the voltage output of the sensor to be in the correct range they suggest to check the resistance across the sensor both hot and cold. Hot, I was reading a resistance of 20+ Kohm. As it is written the manual, any resistance above 2 Kohm means you have a bad sensor even if the voltage readings are correct. So I replaced the sensor and tried it out... still had the power loss issue. At that point I started into the trouble shooting section of the Kohler manual where they suggest properly adjusting low and high idle engine speeds. I found I was running ~3450 rpm under no load, suggestion is 3750rpm.

After making the proper engine speed adjustments my problem was solved. My guess is that continuously operating at low engine speeds caused the engine to run excessively hot and there is an algorithm in the control system that de-rates fueling to protect the engine which would appear as loss in power.

[DanK]

I had my right wheel motor on a xt3200 go out at 180 hours so the dealer loaned me a Kohler 26 efi to use. I wish I woulda known this last Saturday. Maybe I coulda mowed it faster than 12 hours if the engine wouldn't bog. I think it was mainly evident Sunday mowing my own lawn. I noticed with the blades on and not touching uncut grass I was at about 3450 rpms. Kinda low isn't it? Oh well, I hope I get my mower back tomorrow. Mo Power...arghhh...arghhh...arghhh.

[dixieseller]

You need to see if the wiring ground kit has been installed on those 26HP units. Kohler # 24 755 134S

[nardharv]

I bought the unit used... is there a quick way to determine if I have the ground kit. Can I get it a my local Dixie dealer?

[DC Service]

Your local Dixie Chopper dealer either has the part,or can get it quickly.Check with them to see if it is in stock. :)