cold drivability

[Sherman Bird]

I have a 2012 Ram 1500 with an interesting problem, well for me anyway.
It starts normally and well cold or hot. But with cold start, and starting to drive, it has almost no power and there feels to be a slight miss. If it was a carburetted vehicle, I would think that the power valve was stuck closed. Once it warms up it appears to run fine. The other interesting part is that the fuel economy dropped from 21 -22 MPG on the highway down to 14 MPG highway.
The spark plugs were recently replaced with no improvement. Air filter is clean.
Any ideas much appreciated.

It's time for a good scanner to map Fuel control. However, there are 3 things which must be looked at.
1) Air
2) Fuel
3)Correction

A scanner with a VE (Volumetric Efficiency) function can narrow it down in a short test drive.

All PIDs should be evaluated in that there are so many possible culprits. If it only occurs cold, my very first look would be at the value read-out of the coolant temperature sensor and the ambient air temperature value.

get an inexpensive vacuum gauge and read idle vacuum, snap the throttle for a split second to over 2000 RPM and make sure vacuum drops to under 4 inches right quickly. Upon letting the throttle snap back to idle position, you should see over 20 inches of vacuum. This will check for exhaust restriction such as a clogged cat or muffler.

 

[Hagar1]

It's time for a good scanner to map Fuel control. However, there are 3 things which must be looked at.
1) Air
2) Fuel
3)Correction

A scanner with a VE (Volumetric Efficiency) function can narrow it down in a short test drive.

All PIDs should be evaluated in that there are so many possible culprits. If it only occurs cold, my very first look would be at the value read-out of the coolant temperature sensor and the ambient air temperature value.

get an inexpensive vacuum gauge and read idle vacuum, snap the throttle for a split second to over 2000 RPM and make sure vacuum drops to under 4 inches right quickly. Upon letting the throttle snap back to idle position, you should see over 20 inches of vacuum. This will check for exhaust restriction such as a clogged cat or muffler.

Thank you for the info, here is what I've found so far: the coolant ambient and intake air temp are all within a degree after a cold soak over night. The short term on both banks is pretty close to zero, fluctuates +or - about 3 . But, now that I think of it, the long term doesn't make sense .... 12795 on each bank.
The cam is in good shape, recent lifters and a cam inspection. There is no metal in oil, I cut every filter and use a magnetic oil plug.
The interesting thing is, it that happened from one fill up to the next. I always do the math for fuel efficiency every thankful. Like I mentioned previously, I could almost live with the drivability but the fuel consumption is a tough. I suspect that they are related.

 

[Hagar1]

I have a 2012 Ram 1500 with an interesting problem, well for me anyway.
It starts normally and well cold or hot. But with cold start, and starting to drive, it has almost no power and there feels to be a slight miss. If it was a carburetted vehicle, I would think that the power valve was stuck closed. Once it warms up it appears to run fine. The other interesting part is that the fuel economy dropped from 21 -22 MPG on the highway down to 14 MPG highway.
The spark plugs were recently replaced with no improvement. Air filter is clean.
Any ideas much appreciated.

Update .... after much testing and head scratching here is the problem. First of all, yesterday I decided to get to the bottom of this one way or another. I drove the truck on about a 30 mile trip all the while monitoring MAP and a few other sensors. Everything started out fairly normal but as time went by I noticed at steady cruise, the map reading was all over the place. Often dropping to1 inch or less of vacuum with a corresponding change in map voltage.
Now, being a speed density system, it relies on accurate map reading. This would explain the fuel economy problem as well as the cold drivability. I had another tech cross check my diagnosis and he agreed.
Interestingly, it behaved properly at curb idle but acted up when on the road.
Why no code? Well, thevacuum and voltage stayed proportional so the pump didn't ever see "a change to great to be real."
New sensor on its way....

 

[Hagar1]

I have finally made some progress in this headache. Interestingly, I had NO codes until I changed all 4 O2 sensors. Then I started getting some interesting codes so I cleared them, disconnected the battery for overnight and then hooked the battery up and started driving. There it was ..... P0158 the downstream O2 sensor. Now, if you read up on it, the authors of various publications will lead you to believe it is either a bad sensor or a short in the wiring.
Some of my old "diagnostic" ideas crept in and told me to check the injectors on the passenger side. I pulled the fuel rail and looked at the injectors and #6 just didn't look like the rest. I changed them all with some used ones that I had laying around. Took it for a drive and low and behold ......... NO fault codes, no check engine light. And another interesting thing, the "random misfires" are now almost completely gone. Before I did the change, I had random misfires so bad the vehicle would shake.
So, so far, I've changed out all four O2 sensors AND the injectors on the right side.
I'll see what the cold driveability is like tomorrow morning.

 

[RamDiver]

I have finally made some progress in this headache. Interestingly, I had NO codes until I changed all 4 O2 sensors. Then I started getting some interesting codes so I cleared them, disconnected the battery for overnight and then hooked the battery up and started driving. There it was ..... P0158 the downstream O2 sensor. Now, if you read up on it, the authors of various publications will lead you to believe it is either a bad sensor or a short in the wiring.
Some of my old "diagnostic" ideas crept in and told me to check the injectors on the passenger side. I pulled the fuel rail and looked at the injectors and #6 just didn't look like the rest. I changed them all with some used ones that I had laying around. Took it for a drive and low and behold ......... NO fault codes, no check engine light. And another interesting thing, the "random misfires" are now almost completely gone. Before I did the change, I had random misfires so bad the vehicle would shake.
So, so far, I've changed out all four O2 sensors AND the injectors on the right side.
I'll see what the cold driveability is like tomorrow morning.

Awesome and congrats!

And thanks for sharing the information so that someone else might benefit. Please keep up with your updates. They're always greatly appreciated here.

.

 

[Sherman Bird]

I have finally made some progress in this headache. Interestingly, I had NO codes until I changed all 4 O2 sensors. Then I started getting some interesting codes so I cleared them, disconnected the battery for overnight and then hooked the battery up and started driving. There it was ..... P0158 the downstream O2 sensor. Now, if you read up on it, the authors of various publications will lead you to believe it is either a bad sensor or a short in the wiring.
Some of my old "diagnostic" ideas crept in and told me to check the injectors on the passenger side. I pulled the fuel rail and looked at the injectors and #6 just didn't look like the rest. I changed them all with some used ones that I had laying around. Took it for a drive and low and behold ......... NO fault codes, no check engine light. And another interesting thing, the "random misfires" are now almost completely gone. Before I did the change, I had random misfires so bad the vehicle would shake.
So, so far, I've changed out all four O2 sensors AND the injectors on the right side.
I'll see what the cold driveability is like tomorrow morning.

.....and THAT proves that a DTC doesn't mean that particular component is the problem! I deal with this diagnostic reality on a daily basis. The computer is just smart, and stupid enough to report only the DATA! It's up to the mechanic to FOLLOW the data and develop a diagnostic strategy in order to have success in the service bay..

 

[Hagar1]

Another interesting thing is, after I swapped out the injectors on the right side, the misfires decreased dramatically. Next step is to buy a complete set and change them all.

 

[Hagar1]

.....and THAT proves that a DTC doesn't mean that particular component is the problem! I deal with this diagnostic reality on a daily basis. The computer is just smart, and stupid enough to report only the DATA! It's up to the mechanic to FOLLOW the data and develop a diagnostic strategy in order to have success in the service bay..

I always said that the DTC refers to the "circuit" not to the specific component. I was a big advocate on "test" don't "guess."
Just when I think I have solved the problem, after a few days of running sort of ok except for the fuel economy, it jumps up and bites me again.

 

[Hagar1]

I can confirm that the problem started a moth or so before the plug change.
The PCV valve was clean and rattled when I gave it a shake.
In regards to the plugs, I checked the gap on all of them prior to installation. I'm kind of old school that way.
I looked at the adaptives and they flip back and forth between about +2 and -4 on both sides. On a cold soak overnight, both the intake air temp and coolant temp read the same.

Well, I am totally beaten with this problem, there is something that I'm missing. I changed all 4 O2 sensors and started getting O2 sensor codes. These were 100% state of the art Chinesium from Amazon. I pulled them and put in 4 NTK from Auto Value. The O2 codes "seems" to be resolved. The drivability when cold is not great. I drive about 300 yards or so, them come to a stop, make a left turn and start up a hill ....... THAT is where the stumble takes place. It I hold the throttle at that spot, it will eventually resume accelerating. ..... As I have said before, it feels like a stuck power valve on a carburetted engine. No codes now. The fuel economy is down to about 11 to 12 MPG ..... and that is Imperial Gallons. 400 kilometers is the outer edge of range now. I used to run 22 to 23 MPG on highway.
I have spoken with dealership techs and they say, "without codes, we likely won't find anything."
Didn't do an actual compression test but from my years of working around engines, I know the compression is even as in no weak cylinder. I run a magnetic oil drain plug and cut every filter, no metal. I run 5w20 Castrol and add a can of Liquid Moly on every oil change.
Everything we test comes up normal.
So far: New plugs from Auto Value
New lifters, cam was OK
4 new O2 sensors
Test run injectors on right hand side
Retorque intake
checked exhaust for leaks
Installed a "bonding" wire between engine and frame
As I'm sitting here writing this, I think back to the underside of the truck and the "bonding" wires from the exhaust to the frame are corroded off. Could static electricity build "that " fast in the exhaust?

 

[Hagar1]

Well, finally some codes but nothing in the PCM ....... Lots of "communication" codes U0100, U0101, U0401, U0415, U1197 and C2206 ...... All point to a "Comm" problem, possibly the S130 or S131 splice gone bad is my first thought. It seems that they are all common to the PCM, TCM and ABS