Intermittent CEL Code 186

[ddenton749]

Stock 94 Explorer XLT 4.0L Auto 176,000 miles.

The CEL comes on after about 15 minutes of driving. Sometimes it goes off for seconds to minutes then comes on again. Then it usually stays on. I shut the engine off and restart, and the same CEL sequence repeats. There appears to be no difference in how the engine runs either way.

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

Absolutely meaningless. I tried searching for "Code 186" but the search results give me every post with "Code" in it. Does anyone have any ideas?

 

[ddenton749]

Update:

CEL still comes on. Now I have codes 181 and 186 in stored memory. Both suggest the fuel mixture is lean and the computer has made the fuel mixture as rich as it can. KOEO test is fine.

This past Sunday:

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 line to the accessories (vacuum reservoir, air cleaner box, heater valve, etc.) and plugged the tree.
Started it and no CEL. Drove it and at 1.5 miles the CEL came on.
At that point I gave up for the day.

Here it is: The Explorer runs great even with the CEL on. I can start it and let it idle - no CEL. Once I start driving and it reaches operating temperature, CEL comes on. I can shut it off and restart it, and the CEL is off. I drive 1.5 miles and the light comes back on. Occasionally the light will turn off for a minute or two and then come back on and then it stays on until I shut the car off and start it again.

If it is a vacuum leak it is very small and only occurs when the engine is warm and the car is moving. (Which is why I thought Evap system and the air box.) It doesn't affect driveability at all. Does anyone have any other suggestions for where to look?. I have no idea how old the O2 sensors are. They could be original for all I know. The car has 146,000 miles.

Anyone?

 

[MrQ]

Hmm, could be a stuck or slow injector. The computer controls the injectors so it sounds like its commanding the injector to activate and it's staying open longer than it should. Try running some injector cleaner through the tank and see if that helps. Otherwise you will need to pull the upper intake off, disconnect the fuel rail and inspect the injectors for clogs. New ones aren't horrendously expensive.

Also get that vacuum leak fixed. Even a small one can cause issues. And since you are running lean you are dumping quite a bit of fuel into the cats which can cause them to burn up.

 

[ddenton749]

Update Sunday 2/9:

I still have code 186 The CEL comes on a few minutes into driving, after the engine gets to operating temperature. I shut the car off, start it, and drive it for a few minutes and the light comes on again. Somtimes the light goes off for a short time but then comes back on.

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 is new.

I have gone through the Emissions Manual Pinpoint Procedures with a breakout box.

MAF voltage good.
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,

The purge valve was broken but I plugged the purge system at the throttle body.

The car runs extremely well except for a slight rolling idle when I start it cold. This clears up in about 60 seconds.

I replaced the valve cover gaskets a couple of months ago and the PCV valve is new. I replaced the upper plenum gasket at that time.

I have had this code since I bought the car last August.

The O2 sensors could be original for all I know. The car has 147,000 miles.

 

[ddenton749]

Update 2/21/2020

I am still looking for some help.

The CEL still comes on after the engine reaches operating temperature. It will sometimes go off and then back on again randomly, or off after coasting downhill.

I still have Code 186 in KOEO stored memory but not in Continuous memory.

I replaced the Canister Purge Valve. Prior to 2/9 update I removed the purge valve and plugged the port in the throttle body. I replaced it because the plastic hose nipples were cracked. The new valve didn't make any difference.

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.

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.)

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 running at higher-than-normal RPM cause code 186?

 

[ddenton749]

Yep.... I'm still trying to figure this out.

This morning I drove around town. I was easy on the throttle and the car never got above 40 mph. Engine was at normal temperature and the air temperature today is in the fifties. The CEL did not come on in 30 or so minutes of driving.

I know of two things that occur under 40 mph:

The canister purge valve opens only slightly. Pin 11 was between 7 volts and VPWR. At highway speed it should be much lower as the CANP operates more.

The torque converter will be unlocked at this speed range.

When I parked there was a slight odor of gas at the rear of the car. This means there is likely a leak in the vapor lines back there. However, I drove the car with the evap system plugged a couple of weeks ago and the CEL still came on.

I believe the lack of converter lock-up is due to a faulty solenoid. Pin 53 is 14.2 volts (VPWR) normally. It should drop to 0.3 when it locks up but I only see 13.8 volts as if the EEC is trying to engage it. The 3/4 shift solenoid (Pin 51) has correct voltage readings. Perhaps I should check the continuity of the TCC solenoid before I replace it.

Does anyone know of anything else that only functions at higher speeds? That seems to be the only time the CEL comes on - engine at normal operating temperature and vehicle speed above 40 mph.

 

[Turdle]

Just a hunch,
check the TPS sensor for < 1v at idle position rising steady to 4.8v at Wide open throttle, key on engine off.

TPS tip in ( higher voltage) causes torque converter to "unlock" -- could be the TPS output is too high.

If your truck has egr, check the egr tube to intake junction for leaks. I use an un lit propane torch to inject raw propane to the suspected areas while engine is idling, listen for the engine speed to change.

 

[ddenton749]

Right. Good call.

The EGR also functions at higher loads. I will check for vacuum leaks there using a propane torch. Although, when I had the upper plenum off to replace the valve cover gaskets, I replaced the EGR gasket as well. Is that the connection you describe? I have a propane torch.

I still have the breakout box connected so verifying the TPS voltage will be simple.

I will post an update later.

 

[ddenton749]

Just a hunch,
check the TPS sensor for < 1v at idle position rising steady to 4.8v at Wide open throttle, key on engine off.

TPS tip in ( higher voltage) causes torque converter to "unlock" -- could be the TPS output is too high.

If your truck has egr, check the egr tube to intake junction for leaks. I use an un lit propane torch to inject raw propane to the suspected areas while engine is idling, listen for the engine speed to change.

TPS voltage 0.95 to 4.8v KOEO. 0.95v at throttle closed is a little high. It should be 0.8 to 0.9v but I am using an accurate digital volt meter so it is probably close enough.

Running:
0.95v at hot idle, 1.0-1.2v at 30 mph, 1.2-1.5v at 50 mph when the TC should lock up.

I probed all around the EGR (and the rest of the engine) with the unlit torch. I didn't find any vacuum leaks.

I checked the EGR voltages at the breakout box and they are within specifications. All of the voltages appear to be within tolerances.

I drove home from work below 40 mph and light on the throttle. No CEL until I started up a hill. The light stayed on for a few minutes after the hill then it went off. It stayed off until it was under a load again. It stayed on until i got to the pharmacy and shut the car off. The light did not come back on for the ten minute trip home.

I cannot find any suspicious sensors or actuators, other than the TC Lockup solenoid, using the breakout box. I can't find any vacuum leaks either. I am at a loss.

Are the TC and the 186 code two separate problems or are they related?

 

[ddenton749]

Update:

Yes I am still trying to solve this.

Last weekend I replaced the negative battery cable. The old one was falling apart at the terminal. I didn't drive it at all this week. It did start better and idle better cold.

Today I started it to take it to put some gas in it. The CEL came on driving to the gas station but went off again. I got gas (I left it running) and when I drove away the light came on momentarily then I realized the torque converter locked up.

I drove it back and forth on the four-lane road for about a half hour. The CEL would come on at around 45 mph in 4th gear then the torque converter would lock up and the CEL would go off. I tried this several times and the same thing each time. It was working fine.

Then...

I got home shut if off thinking that I may have solved it but I decided to try it again. Now I am back to exactly where I was before. The light comes on a few minutes into driving and stays on. No TC lockup. I shut the engine off, restart it, no light for a few miles then it comes on again.

Code 186.

There has got to be someone out there who has an idea.

 

[ddenton749]

Today:

I disconnected the PCM at the BOB and replaced the IACV. It really didn't make much difference. I noticed the coolant was a little low so I drove it to Walmart a few miles away. It ran well and the torque converter locked up. A few minutes later the CEL came on at 50 mph, right at the time the TC should have locked up then when I slowed down it went off again.

I checked the codes and I now have 172 and 176 - HOS lean, left and right. No 186. If this thing has a vacuum leak it is the smallest leak in history. I can't find it. I assumed it was the CANP system so I plugged it and drove it. The CEL came on in minutes.

It idles perfectly, has plenty of power, and generally runs great.

Ideas, anyone?

 

[ddenton749]

The saga continues...

The good news: Code 186 is gone - for now anyway. I haven't driven it more than a few miles.
The bad news: I now have codes 172 and 176, which I didn't have before.

I replaced the IACV. I replaced it last year but I was always suspicious of it. It gave me a rolling idle when it was cold. The cold rolling idle is gone. (Although it is spring here in PA.)

I replaced the heater core and hoses because I noticed a leak in the core. I replaced the lower radiator hose (original factory hose). I replaced a severely crack radiator fan. (None of these should have anything to do with the codes.)

I tried a different PCM. It made no real difference except:

Now the CEL comes on only briefly, at 50 MPH and normal throttle, just at the moment before the toque converter should lock, then it goes out again and everything works fine TC and all.

I know 172 and 176 are lean O2 sensors which would suggest a vacuum leak. The thing is this Explorer runs REALLY well. It starts right up, has a smooth idle, plenty of power, and no knocking.

A vacuum leak at 50 mph at normal throttle??

This car has 146,000 miles. I am finding that many of the parts are original from the assembly line. I am sure the O2 sensors are old, possible original as well.

I have looked everywhere for a vacuum leak but I can't find it, and the engine runs too well to suggest a leak. The only other thing I can think of is a leak in the EVAP line back near the gas tank. I tried plugging the vapor line to the tank at the canister but it made no difference.

I may try replacing the O2 sensors and see what happens. If nothing else I can rule them out.

 

[ddenton749]

I appears to be fixed.

The truth is, I really don't know what I did to fix it.

The last thing I did was replace the fuel filter. My thinking was that maybe the fuel flow was restricted enough at higher RPM's to cause a lean condition and trigger the 172/176 codes. When I drained the old filter black (yes, black) gas came out. I thought I was onto something. However, I test drove it and sure enough, the CEL came on after about ten minutes.

Two days later (last Sunday) I needed the Explorer to haul some scrap out of my yard. I needed the passenger seat for my helper so I removed the break-out box and re-connected the ECM normally back in it's plastic bracket. It was only a few miles so I figured I would drive it anyway. Low and behold, after two trips to the scrap yard and back the CEL did not come on and the torque converter locked up as it should.

I took it out today (Friday) and drove it about twenty miles in a combination of city, highway, and country roads. It ran perfectly with no CEL. I believe it was either the filter or there was a poor connection in one of the BOB connector pins.

I guess that's it. Kind of anticlimactic, really.

 

[Roadrunner777]

Huh.... I wonder if something else changed, weather warmed up? I have a real question though. On the black gas, in your memory, have you ever used a gas treatment, and if so, which one and how long ago? Just curious...

 

[ddenton749]

Huh.... I wonder if something else changed, weather warmed up? I have a real question though. On the black gas, in your memory, have you ever used a gas treatment, and if so, which one and how long ago? Just curious...

The weather hasn't changed all that much. I bought the car last August. The CEL came on when I was driving it home and I have been chasing the CEL since then. (Here and there. It is not my daily driver.) Last weekend it was in the seventies. This weekend it is in the fifties. I drove it about 25 miles today and it is all good.

As I said, I bought the car last August and I have never used any kind of gas treatment. It is not to say that the previous owner didn't.

 

[bigfoot17]

The weather hasn't changed all that much. I bought the car last August. The CEL came on when I was driving it home and I have been chasing the CEL since then. (Here and there. It is not my daily driver.) Last weekend it was in the seventies. This weekend it is in the fifties. I drove it about 25 miles today and it is all good.

As I said, I bought the car last August and I have never used any kind of gas treatment. It is not to say that the previous owner didn't.

I have intermittent code 181 on 1993 E250. Did your fuel filter change still seem to fix the problem? My van sat for several years. I've run 3 cans of seafoam through it and replaced vacuum lines and other items. Haven't done the fuel filter yet.

 

[Nadams01]

The weather hasn't changed all that much. I bought the car last August. The CEL came on when I was driving it home and I have been chasing the CEL since then. (Here and there. It is not my daily driver.) Last weekend it was in the seventies. This weekend it is in the fifties. I drove it about 25 miles today and it is all good.

As I said, I bought the car last August and I have never used any kind of gas treatment. It is not to say that the previous owner didn't.

Its interesting how you bring up the TCC solenoid. The TCC solenoid has a bunch of different parameters that need to check out before it engages or disengages. (Speed 50, engine temp, brake pressure, vacuum, tps sensor voltage etc.) obd1 is pretty stupid and the voltages set in the PCM that would trigger a CEL are pretty wide. for example using theoretical numbers the acceptable voltage range for a MAF at idle is .2v to 1.3v but in reality a deviation from the .7 volts by .2 volts is enough to cause a rough idle but not trip a code. That's just a simplified example of why OBD1 are so hard to diagnose, so what most likely happened is you had a sensor reading a weird improper voltage that was not enough to set a code for it but enough out of wack that it would upset the TCC solenoid and cause the computer to trip a code for that TCC solenoid. Im thinking about making a post about diagnosing OBD1 through my experience and endevours.