Export thread

Hello!

I just picked up a "new to me" Lazer Z 60" with Kohler EFI engine. This is my first time into the EFI world for mowers so bare with me.

It was only running on one cylinder. Found a coil pack arcing at the boot to the block. I put some heat shrink on the boot and it stopped the arcing. New coils are on the way.

It seemed to run fine at an idle so I took it out for a test run in the yard. Found that it has a significant bog/rich condition under load. You can slowly creep the throttle up and achieve full throttle without the blades on but as soon as it senses a certain load percentage (this is a hunch) it skips a beat and bogs hard and blows some black smoke. You can throttle down and bring the rpm back up slowly and get back to previous rpm but any obscure load and it does the same thing. If you creep the throttle up with the blades on, you can get roughly half throttle before it dives hard.

Fuel pressure was out of spec low by 2 psi so ordered new pump. Running pressure seems low with new pump when looping in pressure gauge to pump outlet but not sure what this spec should be as I cant find any reference in the service manual. I took off the throttle body and intake and ran through the ultrasonic cleaner since the previous owner was also running it without any intake filter.... checked compression, both cylinders at 150 psi. Replaced spark plugs. Hooked the injectors up to a 12v pulse machine and also ran them through the ultra sonic cleaner while pulsing to clear them out of any deposits. reassembled everything with new fuel filter, checked all fuel lines were clear and lift pump was working properly. Had to rebuild the starter so the grounds and power supply were checked, cleaned and reinstalled. Once the intake was put back together with air filters, I did an ECU reset and TPS relearn to the best of my ability and still the bog persists...

I have yet to check the O2 sensor for proper functionality but the check engine light is not on. I have verified the CEL does work properly. Although I am curious, when I unplug the O2 sensor, it does not seem to affect the condition of the engine while running. Nothing changes and no CEL so I am assuming it does not continuously check the sensor signal, rather, the heater circuit within the sensor? Makes me question if the O2 sensor is bad but not bad enough to trip a CEL or code.

Any help would be appreciated.

mczar07 said:

as soon as it senses a certain load percentage (this is a hunch) it skips a beat and bogs hard and blows some black smoke.

Click to expand...

She's running rich. Look for vacuum leaks. EFI might be trying to over compensate for a vacuum leak.

mczar07 said:

Fuel pressure was out of spec low by 2 psi so ordered new pump.

Click to expand...

2psi? Don't think it required replacement. Unless is was deficient in fuel volume??. This is what you need to check, volume. Also your gauge probably isn't calibrated. Yup 2psi is low per the spec per your words. Is it enough to cause your issue??

mczar07 said:

I took off the throttle body and intake and ran through the ultrasonic cleaner since the previous owner was also running it without any intake filter.

Click to expand...

Ummm, ummm, ummmm. Do we need to touch on this one?

I would look into your O2 sensor. Need to get a wideband O2 meter. See what the A/F ratio really is. Again from up top you said it was lazy and puffing black smoke.

Or that is some dumb EFI system that doesn't read the O2?? Like an old school mechanical FI.

39 psi +or-3 psi Most of the time when you unplug the O2 sensor it will run ok.

I would fondle the wires from the O2 back up to where it originated from. Feel for zips in the wire. Computer and any EFI modules grounded cleanly. Main battery ground supreme.

Is this liquid cooled? Is there an engine temp or coolant temp sensor on this hooptie?

It would not read anything as it is running in open loop only reads through O2 sensor in closed loop

hlw49 said:

39 psi +or-3 psi Most of the time when you unplug the O2 sensor it will run ok.

Click to expand...

Take the vent hose off the top of the fuel pump module and see if it has fuel in it. Should not have, vents into the intake and would cause this problem.

hlw49 said:

It would not read anything as it is running in open loop only reads through O2 sensor in closed loop

Take the vent hose off the top of the fuel pump module and see if it has fuel in it. Should not have, vents into the intake and would cause this problem.

Click to expand...

you might take a hose and put it on the vent fitting and put it in a bottle or something and start and run the engine and see if it clears up.

slomo said:

She's running rich. Look for vacuum leaks. EFI might be trying to over compensate for a vacuum leak.

2psi? Don't think it required replacement. Unless is was deficient in fuel volume??. This is what you need to check, volume. Also your gauge probably isn't calibrated. Yup 2psi is low per the spec per your words. Is it enough to cause your issue??

Ummm, ummm, ummmm. Do we need to touch on this one?

I would look into your O2 sensor. Need to get a wideband O2 meter. See what the A/F ratio really is. Again from up top you said it was lazy and puffing black smoke.

Or that is some dumb EFI system that doesn't read the O2?? Like an old school mechanical FI.

Click to expand...

Ok so I replaced the O2 sensor and no change, installed the new injectors, no change, coils came in so those as well, no change. Did an ether test to find vacuum leaks with no indication of a leak.

slomo said:

I would fondle the wires from the O2 back up to where it originated from. Feel for zips in the wire. Computer and any EFI modules grounded cleanly. Main battery ground supreme.

Is this liquid cooled? Is there an engine temp or coolant temp sensor on this hooptie?

Click to expand...

Checked all grounds with none looking corroded or loose. O2 wires wiggled while running well and while running poorly with no change in either circumstance. No coolant but it does have an external oil cooler.

hlw49 said:

It would not read anything as it is running in open loop only reads through O2 sensor in closed loop

Take the vent hose off the top of the fuel pump module and see if it has fuel in it. Should not have, vents into the intake and would cause this problem.

Click to expand...

I checked the vent hose and it appeared damp but no fuel running out. I ran the engine with the vent hose removed and it acted exactly the same. Could this indicate there is a vacuum leak somewhere in the vent line to throttle body? I did replace this hose due to it breaking upon disassembly. Inspecting now

mczar07 said:

I checked the vent hose and it appeared damp but no fuel running out. I ran the engine with the vent hose removed and it acted exactly the same. Could this indicate there is a vacuum leak somewhere in the vent line to throttle body? I did replace this hose due to it breaking upon disassembly. Inspecting now

Click to expand...

Ok the hose is before the butterfly valve so it doesn't see vacuum really. I did find a chewed up oring on the map sensor. Attempted repair with slightly bigger oring and now I have a map sensor on order ?‍

This is there trouble shooting guide out of the service manual for this engine. Engine Loses Power ● Dirty air cleaner element. ● Engine overheated. ● Excessive engine load. ● Restricted exhaust. ● Faulty spark plug(s). ● High crankcase oil level. ● Incorrect governor setting (on engines equipped with electronic throttle body governor is digitally controlled and not adjustable). ● Low battery. ● Low compression. ● Low crankcase oil level. ● Quality of fuel (dirt, water, stale, mixture).

hlw49 said:

This is there trouble shooting guide out of the service manual for this engine. Engine Loses Power ● Dirty air cleaner element. ● Engine overheated. ● Excessive engine load. ● Restricted exhaust. ● Faulty spark plug(s). ● High crankcase oil level. ● Incorrect governor setting (on engines equipped with electronic throttle body governor is digitally controlled and not adjustable). ● Low battery. ● Low compression. ● Low crankcase oil level. ● Quality of fuel (dirt, water, stale, mixture).

Click to expand...

Thanks for the info. Iv'e been going through it as well and have done the following:

- installed air filter, changed oil and filter to proper level, checked compression, new spark plugs, new coils, reset the governor adjustment, charged and load tested battery, changed fuel, fuel filter, fuel pump, injectors, ECU reset, TPS relearn, new O2 sensor. MAP sensor is on the way since I damaged it when reinstalling it. There was a smashed O-ring on it which could have been causing the air leak, I just figured that it would have more of an issue at idle when vacuum is at it greatest. At idle, it runs perfect only has an issue when you load it up at high RPM.

When you are saying CEL I assume you are saying check engine light. Does this mower have a MIL light malfunction indicator light that will blink codes or are they calling it a check engine light. Anyway will it blink codes?

hlw49 said:

When you are saying CEL I assume you are saying check engine light. Does this mower have a MIL light malfunction indicator light that will blink codes or are they calling it a check engine light. Anyway will it blink codes?

Click to expand...

It will blink codes if I unplug a sensor but there are currently no codes flashing on the MIL or CEL as I was calling it. I changed the broken map sensor with new and still has same issue. I'm not sure what else to do.

If this mower is running that bad and is throwing no code how are you trying to read the codes.

hlw49 said:

If this mower is running that bad and is throwing no code how are you trying to read the codes.

Click to expand...

There aren't any codes unless I unplug a sensor. At that point, I read the flash codes from cycling the key to get them to flash. After I know those codes aren't causing an issue, I do an ECU reset and a TPS relearn

mczar07 said:

There aren't any codes unless I unplug a sensor. At that point, I read the flash codes from cycling the key to get them to flash. After I know those codes aren't causing an issue, I do an ECU reset and a TPS relearn

Click to expand...

What procedure are you using to read the codes????

hlw49 said:

What procedure are you using to read the codes???

Click to expand...

the procedure from the manual.
1. Check that the batt ery voltage is above 11 volts.
2. Start with the key switch OFF.
3. Turn the key switch to the ON and OFF, then ON
and OFF, then ON, leaving it on in the third
sequence. Do not start the engine. The time
between sequences must be less than 2.5 seconds.

Check computer ground and power.

new map sensor replaced. I ended up getting the Kohler diagnostic software for the live data views. looks like when the engine goes into "power enrichment" in the ecu, the issues start to happen until the throttle is dropped down and "power enrichment" becomes disabled.

slomo said:

Check computer ground and power.

Click to expand...

power and ground are ground are good. I ended up getting the Kohler diagnostic software and I am seeing that the engine wont stay in closed loop at high rpm. could this be causing the issue? also seeing on the software that when the engine goes into "power enrichment" is when the engine starts having issues. if i lower the rpm until the engine comes out of "power enrichment" mode, then it smooths out.

Some engines don't look at the O2 under full beans. I don't know about yours. Power enrichment I would think, would be increased rpm's or engine load. Sounds like more fuel is being dumped by the computer.

Are there any computer upgrades offered for this?

First post from google. On another site.