Odd symptoms P0336 Code

[m1949]

Since cold weather set in I occasionally experience rough idle at start up and hesitating acceleration for maybe 5 minutes. Then everything smooths out. This only happens when it's cold outside and the truck is cold, and not all the time even then. It runs and accertlates smoothly once the engine warms up. I ran an OBD and pulled code P0336, crankshaft position sensor. A new sensor was installed about 12K miles ago when the engine was installed and received a custom tune. But we used the old connector. Does this sound like a faulty connector, or have any of you had similar symptoms from a bad sensor? Thanks.

 

[MassHoe04]

There is a chance that the rough idle when cold could be unrelated to the P0336 code.

If you have a Tech 2 (or access to a bi-directional scanner) that will allow you to do a CPS re-learn, you might see if the code returns afterwards.

On rough idle when cold, there is often a condition that happens where there is a leak on the intake or exhaust manifold that allows extra air to enter the system. That can throw off the upstream O2 sensor readings of the MAF readings. Then the system thinks things are too lean, so starts pumping more fuel in. Too much fuel. Then whatever gap is there closes up when parts heat up and expand, cutting out the intake of excess outside air. After the airflow gets back to normal, things smooth out again.

Just a theory. But I can't see why the CPS would be having issues in cold weather and not when warmed up too...

I had an exhaust leak on my 05 Jeep Rubicon. It was at the at the flange between the manifold and the collector pipe (above the upstream #1 O2 sensor). Rough idle. Excess fuel burning and smooth after warm-up.
If any of this helps...

 

[MassHoe04]

I would look at STFT1 and STFT2 on a cold start to see if the system is drowning in excess fuel or not. Just to rule that out.

 

[m1949]

There is a chance that the rough idle when cold could be unrelated to the P0336 code.

If you have a Tech 2 (or access to a bi-directional scanner) that will allow you to do a CPS re-learn, you might see if the code returns afterwards.

On rough idle when cold, there is often a condition that happens where there is a leak on the intake or exhaust manifold that allows extra air to enter the system. That can throw off the upstream O2 sensor readings of the MAF readings. Then the system thinks things are too lean, so starts pumping more fuel in. Too much fuel. Then whatever gap is there closes up when parts heat up and expand, cutting out the intake of excess outside air. After the airflow gets back to normal, things smooth out again.

Just a theory. But I can't see why the CPS would be having issues in cod weather and not when warmed up too...

I had an exhaust leak on my 05 Jeep Rubicon. It was at the at the flange between the manifold and the collector pipe (above the upstream #1 O2 sensor). Rough idle. Excess fuel burning and smooth after warm-up.
If any of this helps...

I thought of an intake leak and had it smoke tested. Sure enough, there was a small leak from a port gasket. We installed all new gaskets, retested, and no leak. But we are still getting the P0336 Crankshaft sensor code. My thought is the connector wiring may be faulty and loses signal when cold weather causes a slight contraction in the wire. Then, when the engine warms up the wire/connection expands just enough to restablish signal.

 

[MassHoe04]

I thought of an intake leak and had it smoke tested. Sure enough, there was a small leak from a port gasket. We installed all new gaskets, retested, and no leak. But we are still getting the P0336 Crankshaft sensor code. My thought is the connector wiring may be faulty and loses signal when cold weather causes a slight contraction in the wire. Then, when the engine warms up the wire/connection expands just enough to restablish signal.

Certainly a possibility. New connector seems like it would be cheap enough to try.

 

[m1949]

I would look at STFT1 and STFT2 on a cold start to see if the system is drowning in excess fuel or not. Just to rule that out.

Wouldn't I be pulling an O2 sensor code if fuel trim is off?

 

[MassHoe04]

If it thinks the amount of fuel is within range for the amount of air maybe no code.

On my Jeep, I was not getting any O2 sensor code. I am guessing that because the excess air coming in (according to the upstream sensor readings) was making the computer think it was starving for fuel, it upped the fuel coming in. Possible the fuel/air ratios were still in the parameters of what the O2 sensors were expecting to see, but still making it run rough until the leak sealed itself when warmed up.

If air/fuel ratios are tweaked enough to make things the wrong amounts but right proportions, it is possible that it could escape without tripping a code.

I am sure there are other members more qualified than me to help you sort through the weeds on this.

Just relaying the little bit I experienced, with the chance it may help.

I would still be curious to see fuel trims during the first few minutes of the cold start. If nothing else, just to confirm there is nothing weird going on with air/fuel.
Cost nothing for that and might be helpful.

 

[m1949]

Took the Escalade back to the builder to correct a few issues. Among other things, he replaced the Crankshaft position sensor connector (pigtail) which cleared the p0336 code. He also did some paint correction and swapped out the Street Performance shocks for a set of Bilsteins. The ride is much smoother. Also had the tuner/programmer check the fuel trim and he tweaked the shift tables in the tranny. We talked about the good fuel economy the truck has. I averaged 20.6mpg for 650+ mile roundtrip with a stiff headwind going. Averaged 19.1 mpg for the tank of gas fighting the headwind. That was running ~75MPH most of the time. He told me since I mentioned wanting better fuel economy at the time he did the tune he did some "refining" of injector settings. I may not be saying this correctly, but I understood he tweaked for better fuel efficiency at low rpm cruising, for idling, and for slower rates of acceleration. Upshot is everything is working great! He told me he's not surprised at the mileage, nor that some folks think I'm lying!