I have a 1994 Explorer, the Ranger's brother. I have had no success on the Explorer forum.

Stock 94 Explorer XLT 4X4 4.0L A4LD 147,000 miles. This is not my daily driver. It is more of a backup/bad weather/utility vehicle. I have all of the original 1994 factory service manuals including the Powertrain Control/Emissions Diagnostic Service Manual. (Thanks to eBay.)

The CEL comes on after about 15 minutes of driving (after the engine reaches operating temperature. Sometimes it goes off for seconds or minutes then comes on again at which point it stays on. I can shut the engine off and restart, and the same CEL sequence repeats. I have had this code since I bought the car last August.

Only one code is stored in memory: 186 - Injector pulse width higher than expected.

There appears to be no difference in how the engine runs either way. The car runs extremely well except for a slight rolling idle when I start it cold. This clears up after about 60 seconds.

I realized that if I drive it very light on the throttle the CEL does not come on. It comes on when the engine is under a load.

I also realized the torque converter does not lock up, even when the CEL is off. The voltage at the breakout box does not change to indicate TC lock-up at speed. Also, there is no difference in RPM at 55 mph when I step on the brake. (The BOO switch works.)

Thinking that I have a small vacuum leak and the leak only appears at normal operating temperature and the car is moving:

I found a leak in the vapor line between the canister and the tank. Fixed it. Started the car, let it warm up. No CEL. Drove it and at 1.5 miles the CEL came on.

Returned to the garage and I disconnected the EVAP system at the manifold and plugged the manifold port. Started it and no CEL. Drove it and at 1.5 miles the CEL came on.

Returned to the garage and I disconnected the vacuum lines to all of the accessories (vacuum reservoir, air cleaner box, heater valve, etc.) and plugged the manifold tree. Started it and no CEL. I drove it and at 1.5 miles the CEL came on again.

At that point I gave up for the day.

Next attempt:

KOEO - Code 186
KEOR - no codes
Cylinder Balance test - ok (90)

I have checked every vacuum system I can find. I am 99.99% sure that there are no vacuum leaks. The intake tube (MAF to throttle body) is new.

I have gone through the Powertrain Control/Emissions Diagnostic Service Manual Pinpoint Procedures with a breakout box:

MAF voltage good and all other voltage readings appear good.

Fuel pressure 30 psig regulator connected, 40 psig regulator disconnected. Fuel pressure holds at 30 psig for more than a minute after I shut the car off.

IACV is new enough.

I replaced the power brake booster check valve and grommet,

I replaced the Canister Purge Valve. I replaced it because the plastic hose nipples were cracked. The new valve didn't make any difference.

I replaced the valve cover gaskets a couple of months ago because of oil leaks. I replaced the PCV valve at the same time. I replaced the upper plenum gasket as part of the valve cover gasket replacement.

The O2 sensors could be original for all I know. They are difficult to test since the voltage switches during operation.

I have been driving around with the breakout box connected and I have been checking all of the sensor and actuator voltages. All of the readings seem to be within 0.5 volts of what they should be according to the Powertrain Control/Emissions Diagnostic Service Manual.

Are these two (code 186 and no TC lock-up) related? I would understand no TC lock-up with the CEL on, but it should work when the CEL is not on (the EEC does not see a problem). I am thinking I may have a bad TC lockup solenoid in the valve body. Could the engine operating at higher-than-normal RPM cause code 186?

Does anyone have any ideas as to the cause of code 186?

After doing a Google search I found these posts, check out these posts from the Escort forum about that same code.
https://www.feoa.net/threads/error-c...rcuit-h.71168/
In this next link the last post he explains what fixed the code.
https://www.feoa.net/threads/fault-c...6.86143/page-4
Check this post from 2009 on the Explorer forum with the same complaints you described you are experiencing. Post #-3 explains what he did to fix the problem
https://www.explorerforum.com/forums...de-186.256453/
I hope this helps you fix your problem.

__________________
2000 Ranger Extd Cab XLT, 4X4 Off Road, 4.0L, Auto, 8.8 - 4.10's, 01 grille & lights swap.
69 Mustang, modified 5.0, & 5spd.(project)
99 Explorer Sport, 4.0 SOHC, Auto, 8.8 - 4.10's, PW, PL, PM, Cruise, Tilt. (Wife's DD)
05 F-150 2WD Regular Cab. ( My DD)