2010 SHO Running Rough...

[gdavenport]

All, I've been working through a bug that has my 2010 running rough. According to the codes, it had low starting fuel rail pressure (lift pump) and a cylinder misfire. I changed the plugs, and cleaned the injectors. The car is still running rough(rich?) and is showing 10"Hg (PID through the OBDII scan read). It smokes copiously, especially underload.

I pulled the upstream O2s to check function in Open Loop and the car runs better, but still smokes. In closed loop, the fuel trims quickly run to -30 (maximum allowed) on both banks.

What could be causing this?

The OBDII ports show full function (sensors vary based on conditions) for:

Throttle position(all sensors)
MAP - varies between boost and up to 28"Hg, settles at 10 at Idle
Fuel rail pressure (High side) varies from 65psi up to 1500 (maximum I can see at light/medium throttle)
IAT reads through the range
ECT reads through the range


Does this sound like a mechanical problem or a faulty sensor? I welcome your thoughts.

[SHOdded]

Smoke color/smell?  Thinking bad/leaky fuel injector or possibly blown gasket.

When did this problem begin, and how much has the car been driven since?  Hopefully the O2 sensors & cats are not fouled.

[BiGMaC]

Smoke color/smell?  Thinking bad/leaky fuel injector or possibly blown gasket.

When did this problem begin, and how much has the car been driven since?  Hopefully the O2 sensors & cats are not fouled.

Same questions and Manu... and is the smoke equally from both tailpipes?   AC on vs AC off? On a cold start does the engine slow after O2 sensors warm up... or stay in open loop?

[Courier6]

What are your mods?

[gdavenport]

The car is stock.

The smoke started immediately (5 miles) after addition of fuel injector cleaner was added to the fuel system.

The smoke smells rich, and is like cold operation OL conditions (which it is). I'll throw the new HEGO sensors in there to let it go closed loop and see what happens.

Here is a video showing it:
http://youtu.be/0QIgHP9UwiY

Incidentally, the cause of tearing down the car to the intake ports were the following:

1. Fuel rail pressure was instantly dropping to zero at key off
2. Engine was flooding to the point of hydrolock on start
3. MIL codes for low cranking fuel pressure
4. soiled plugs
5. rough idle/stall
6. copious acrid smoke from exhaust

After the tear down, I found standing fuel on the port side of the intake valves on Cylinder 2 and 5. (other cylinders were ridiculously coked up, but dry).

I replaced the fuel injectors on 2 and 5.

Example of coking on intake port of head (Typical for all ports)

http://1drv.ms/1Bd4OVa

Here is the driest port in the engine(still heavy coking)

http://1drv.ms/1Bd53Qc 

[gdavenport]

Smoke color/smell?  Thinking bad/leaky fuel injector or possibly blown gasket.

When did this problem begin, and how much has the car been driven since?  Hopefully the O2 sensors & cats are not fouled.

Same questions and Manu... and is the smoke equally from both tailpipes?   AC on vs AC off? On a cold start does the engine slow after O2 sensors warm up... or stay in open loop?

Compression test numbers indicate (5 cycles, open cylinder, cold) 185-190psi across the board.

Car has been driven 12 miles (primarily testing) since the issue. I've replaced the fuel, injectors, and will replace HEGO sensors next. 

The smoke is not even and is 70% front (drivers tail pipe) 30% rear (passenger).

There is no smoke when cold, AC on/off makes no difference.

[SHOdded]

What cleaner did you use?  Techron, Seafoam, etc?  Since fuel goes directly into the combustion chamber, it does not wash the back of the valves like in port injected systems.  The more the PCV blowby, the more the coking you see.  Induction cleaning or walnut shell blasting can get at the builtup carbon though.

When you prime the fuel pump (without starting), how much pressure do you see at the rail?  Does it hold or drop right away?  Faulty LPFP or regulator are what I would consider culprits right now.

[gdavenport]

It was an autozone fuel based cleaner run through the tank.

Fuel rail pressure is 65psi at the rail and comes up pretty quickly from key off to RUN when cranking.

I can't figure how the Lift pump or the regulator are the issue as the LP system is rock solid when running?  The HP volume solenoid and sensor control the fuel delivery quality (with injector pulse width) to a much higher degree of accuracy.

With the WB HEGO sensors (Upstream) back in place, the car goes closed loop quickly when warm and fuel trims appear to be <5% unless load is put on the engine. 

When moving and loaded (any thing higher than 30% absolute), the STFTs go to max negative.

Thanks for the thoughts.

[gdavenport]

Follow up. After R&R the turbos and cleaning all the lines, I have the car assembled and back on the road.  The fuel trims are now back in line and it looks like I was just too premature on calling it fixed.


I found very little oil in any of the intake lines and I found that the turbine shaft radial and axial play within tolerance.

The car is running flawlessly now with no smoke, no drivability concerns and is allowing throttle, spark and fuel adjustments as expected.

Those two injectors fixed the issue.

[SHOdded]

Good to hear!  Fuel injectors need to be pushed higher up on the suspect list in such instances.

[gdavenport]

Indeed.  My issue was not trusting the 'fix'.  Allowing the car to "burn in" with new parts is a patience game.  Luckily, I decided to keep driving since the STFTs and LTFTs seemed to be semi-controlled.

Thanks for the help and suggestions, all!

[FoMoCoSHO]

Yeah, its gonna take the ecu some time to trim the fuel from the extreme conditions it was seeing.

Did you pull the battery cable after the repairs?

That would reset the trims and tell you pretty quick if the problem was persisting.

Glad it worked out for you.

[gdavenport]

Reset the battery:

Pull the cable, foot on the brake (drains the KAM capacitor in the PCM) for 30 seconds, reinstall the cable restart.

Or, if you have a tuner, flash to stock, flash to whichever tune is desired. (this is slower, but doesn't involve any wrenching... )