Flashing Engine Light

[Daveos]

Shop foreman at the dealership said he thought it might be a leaking fuel injector. He told me to pull the rail off when it was hot and turn the key on to pressurize it. Put some cardboard under the injectors to see which one was leaking.

 

[JLRockies]

A flashing CEL means "hey, stop driving, your cat is melting" for realz.

 

[Daveos]

A flashing CEL means "hey, stop driving, your cat is melting" for realz.

Thanks for the obvious. I am fully aware that a flashing engine light means stop driving. Unfortunately it only flashed for about 2 or 3 seconds while I was losing power, then went back to running normal before I had a chance to pull over. I do believe I said that in my very first post.

Going to pull the fuel rail today and see if there is a leaking injector.

 

[Daveos]

new injector, new orings on all injectors, no change.

I am thinking it is electrical. When I was on the way home from class today it started cutting out bad like usual. I hit a red light, and turned it off, turned it back on, and whalaa, ran perfect. Maybe something is going screwy on the warmup cycle with some sensor I have not changed yet. About ready to sell it.

 

[pethichammer]

When the Examine Website lighting is blinking, this is the worldwide icon for "P0300-Random Cyndrical tube Misfire". Most generally, this will basically be a tune-up. If the lighting has JUST beginning blinking, this implies the on-board pc "sees" a misfire in several tubes, it just isn't sure as to "what" is producing the misfire. Before getting in touch with this a tune-up, your best bet is to have the "p-codes" study from your pc to see if there are any others besides the P0300. If there is, deal with those first. For example, if there is a P0304-Cylinder #4 Misifre, this could be a substandard key coils, petrol injector, etc... that is results the other tubes. If there are no other requirements besides the P0300, the best beginning point is with ignite attaches and a tune-up.

 

[Daveos]

Doing some reading, it sounds like something is going wrong when the PCM is going from open loop to closed loop on a hot start. The PCM doesn't go into closed loop until operating temperature is reached. This is exactly when the jeep starts to run rough and lose power on warm starts. If it cools off for a while it doesn't take long to warm back up. It starts cutting out right when the temp is at half way. This leads me to think sensor. I have changed most of the input sensors to the PCM.. ...

 

[Daveos]

Interpreter?

I picked up an autoscanner OBD II scan tool. Here is what I found during the cutout period of the warm - warmup cycle where my engine is cutting out bad.

The scan tool was working fine until the engine started to cut out, then it said
"Mod 10 not responding" "Mod 18 not responding"

Pulled from Autoscanners site.

"Mod $##
Appears only when viewing codes. Indicates the computer module that reported the code."

Which computer modules are 10 and 18?

Data Ranges:
TPS was 14.1 to 14.5
MAP hovered right at 10
Coolant was around 203
IAT (Intake Air Temp) was 154

These started to twig out bad when the engine was going rough:
ST FTRM1 was around 0.0 to -0.8
LT FTRM1 around -3.9
ST FTRM2 0.0 to 1.6
LT FTRM2 -3.9ish

Two of them started to throw out crazy values over 10 during the time the engine was cutting out. They are listed as the Short Term Fuel Trim Banks. I have no idea what that is.

All 4 of the O2 sensors seemed within range near warmup - from .2 - .8

I found it interesting that the scanner tossed out the error on Mod 10 and Mod 18 right when the engine started to run bad. Also, that the Fuel Trim Banks were twigging out. Any ideas???!??!!!!??

Thanks

 

[Daveos]

For round two I let it cool off more. Most sensors were the same.

Start Jeep:
ST FTRM1 = 0
LT FTRM1 = -10.2
ST FTRM2 0.0
LT FTRM2 -10.2

As it warms up, throws same error codes. Modules 10 and 18 stop reporting.

Warms up and runs like crap
ST FTRM1 = jumps from 0 to 10 to 13
LT FTRM1 = jumps around -10.2
ST FTRM2 = jumps from 0 to 13 then drops dramatically to -23 ish.
LT FTRM2 = jumps from -10.5 to -33 (jeep is running like crap by now)

Jeep starts to stabilize after about a minute:
ST FTRM1 = around -0.8
LT FTRM1 = around -3.9
ST FTRM2 = around 0.0 to 1.6
LT FTRM2 = around -3.9ish

I guess the question now is, what are modules 10 and 18, and why is the short term and long term fuel trim banks going crazy.

 

[Daveos]

Well, for anyone still following this. I believe the problem has been located. Hopefully be able to confirm tomorrow.

It was pointed out on another forum that if the voltages of the O2 sensors are not dropping to between .2 - .8 before it enters closed loop operation, it will think the engine is running way to rich and lean it out. This is what is happening. My short term fuel trim dropped to -33 for the time the engine was cutting out. On my scan tool, my O2S22 sensor was hovering at 1.6 volts when it entered closed loop, the engine immediately started to run like crap when it hit closed loop because of the bad reading from the O2 sensor. Within about a minute the O2 had dropped down to the values the others were at hovering at .2 - .8 and the engine was running fine. I am going to swap out this O2 tomorrow and see if that fixes it.

Also explains why it is only happening on a warm start. On a cold start, it takes longer for the PCM to enter closed loop operation (at operating temp) and the faulty O2 has time for the voltage to drop before the PCM starts getting data from it. On a warm start, it enters closed loop operation sooner, and the faulty O2's voltage is still too high, making the PCM think the engine is running way to rich, so it cuts fuel.

Fingers Crossed.

 

[TwoBobsKJ]

Gotta say, you've been tenacious with the diagnosis of this problem. If the O2 sensors are it you've helped a lot of Jeepers here in the future.

Thanks for your posts.arty52:

Bob

 

[Snail Farmer]

I've come to the same conclusion myself. I'm gonna be replacing my o2 sensors for the second time tomorrow morning, this time using the OEM NTK sensors. I'll post also if it fixes my problems.

 

[JLRockies]

Thanks for the obvious. I am fully aware that a flashing engine light means stop driving.

Then stop driving.

 

[Daveos]

Gotta say, you've been tenacious with the diagnosis of this problem. If the O2 sensors are it you've helped a lot of Jeepers here in the future.

Thanks for your posts.arty52:

Bob

I replaced the 2/2 and 2/1 o2 sensors. Did the trick. Went with NTK as suggested. Both of them were hovering well over 1 volt when the system went into closed loop operation. This sent the fuel trim strategies way out of whack, cutting fuel to the engine.

 

[Daveos]

Then stop driving.

Again, thanks for your pointless contribution.

 

[rockymountain]

No CEL for the O2 sensors? I think this may rule out always getting a CEL from a lazy O2 sensor.

I must say, your diligence has really paid off. Just ignore mr bad ass. Everyone else does.

 

[Daveos]

No CEL for the O2 sensors? I think this may rule out always getting a CEL from a lazy O2 sensor.

I must say, your diligence has really paid off. Just ignore mr bad ass. Everyone else does.

I cant take all the credit, not sure what forum policies are about mentioning other forums, but a member on another forum was very helpful and gave me the diagnosis even before I was able to test it.

He said he has seen the o2 sensors go lazy enough to screw with fuel strategies but not to the point where they throw a code. I think this was happening with mine. I have to say, this little el cheapo 140$ scan tool has helped me out a lot.

 

[Daveos]

I've come to the same conclusion myself. I'm gonna be replacing my o2 sensors for the second time tomorrow morning, this time using the OEM NTK sensors. I'll post also if it fixes my problems.

Napa had a neat o2 removal slit beefy socket for the job. Made it way easy. The bottom ones are easy. For the up stream right (2/1) I had to use two long extensions, take out the air intake box, and it was easy from there. I haven't changed the 1/1 and 1/2 yet. They look easy to get to as well.

Hope it solves any issues you're having.

 

[Snail Farmer]

Well I replaced both upstream o2 sensors this morning with OEM NTK's, and just drove around for an hour. Everything seems to be good now. Gotta make another 200 mile trip tomorrow. If it handles that fine, I'm gonna call it fixed

 

[Daveos]

Few days of driving, no power loss on warm starts. Can report it was the upstream 2/1 O2 causing my problems.

What about you Snail Farmer?

 

[Snail Farmer]

Replaced my upstreams yesterday morning, been driving a good bit, running like a dream so far.