Aaroneous

Hey guys,

I've spent some time searching on fuel delivery, and I'm having some trouble diagnosing the issue I'm having. Over the course of the last 2 months I've been having intermittent issues that present like fuel pump failure, but have persisted since replacing the pumps.

Truck is an '05 CTT with 123k miles.

Early Symptoms:

• In the beginning, maybe 20% of the time I would get a lazy start and once it fired, it would have an almost complete loss of power when driving. The thing would hardly get out of its own way. If I restarted, it would start on the first crank and I would have normal power. The pump would prime when the driver door opened and did not appear to be linked to the lazy start.
• The next symptom was that I started to have the same loss of power intermittently regardless of the lazy start, and that progressed into occasional stalling when idling at stoplights or when parked after driving. The truck would start back up lazily and run again with poor power.
• When the power starts to come back, it pulses and surges when accelerating (without turbo pressure change) even at under 50% power.
• Slowing to a stop, there is a rough dip in RPM before the engine will settle at normal idle.
• Shifts are rough when in this condition.

Diagnostics completed:

• Pulled fuse 14 and idled fine. Drove to get some coffee and while idling waiting for my wife to come back out, it stalled. Restarted, and had the same loss of power as before.
• Replaced fuse 14 and removed fuse 13 and idled fine. I did not drive around with the secondary pump disabled.

Because pumps are a "when" and not "if" failure and I'm around the right mileage for them to fail, I replaced them last weekend and got 4 days of perfect performance before today when the symptoms listed below returned exactly as they presented before. I stopped at a stoplight this morning and the truck shut down as if I had turned the key off. Very lazy start, then almost complete lack of power when driving -- could barely get up a moderate hill. Pulled over, shut down, restarted, totally fine.

Thoughts/questions...

• The fact that the problem presented with both the primary and secondary pumps isolated pre-replacement proves that the pumps were not in a "failed" or "failing" state.
• Other potential culprits? FPR? MAF? Sensors?
• Is there any information that could be pulled from the computer at Autozone that would help diagnose? If not, would Durametric expose anything different?

Thanks for any insight you can provide. I'm close to just taking it to a shop, but I'd really like to understand the problem before throwing in the towel.

Cheers,

Aaron

Aaroneous

UPDATE:

I've never been so happy to see a CEL in my life. FINALLY some direction!

P0335 - Crankshaft Position Sensor "A" Circuit
P0335 - Crankshaft Position Sensor "A" Circuit Range/Performance
P1175 - Intake air temperature sensor – over limit value

The CPS is an easy fix - pretty inexpensive for the Bosch part from Pelican. Does the IAT code indicate a MAF issue? Do I need to plug into a Durametric to figure out which bank to clean/replace?

Thanks!

Aaroneous

I know I'm super active on my own thread here, but in case it helps anyone with the same issue it turned out to be the CPS. Took about an hour to get the old one out and new one in (didn't have to remove the intake manifold), and the symptoms have disappeared (knock on wood).

Will report back if that changes.

wrinkledpants

*pokes head in. Sees Aaron playing with himself in the corner. Nods approvingly*

Rotmilky

Aaron,

Did your symptoms first start with intermittent loss of power while cruising? My 2008 S today started to act a bit weird. First I was crusing at about 60 on the interstate when I felt a loss of power. It was as if I was coasting for a few seconds. Then everything normal. Pulled off the interstate and had to stop at an intersection. When I went to go through the intersection, there was a loss of power. The engine did nothing for a second or two, even with the throttle to the floor. Then a bit of a burble and then it roared back to live. Since I had the throttle to the floor, I roared through the intersection like an idiot. Then crusing about 30 mph it lost power a couple more times. Same thing...loss of power for a second and then it seemed normal.

Did yours by chance start out this way before it started stalling? I've not had any stalling issues yet.

--Von

Aaroneous

Nope. Symptoms started with intermittent lazy starts and loss of power any time the start was lazy - restarting the car would generally temporarily fix the problem (until it got much worse).

AO

This EXACTLY describes what's going on with my 05TT. Scanned the car today and got P0335 Just ordered a replacement sensor. Will report back if it solves issues like it did for Aaron.

DWPC

Did you replace the fuel filters?

AO

No. My issue is intermittent, just like the OP's, but it's getting worse (more frequent) - plus I just threw a code for this sensor like the OP.