Need Help -- New PCM, Now surging acceleration
2004 6.0L with 150k miles. Need some help here. I think my shop is clueless. It's a long story to how I got here, so let me cut to the chase with what's going on currently and then explain more if needed. I've had ALOT of work done on it in the past -- New FICM, oil cooler, EGR cooler, turbo, #8 injector, and more but it's been a while since I've had any engine trouble.
Had a new PCM & instrument cluster installed to address an issue with the gauges. ($1700 so far!) It was running perfectly when I dropped it off except for the random instrumentation issue. Now, after the instrument cluster & PCM replacement, it's surging when accelerating. What I mean is that you step on the throttle (doesn't matter how hard) and it powers forward (surge) and then lays back for a split second like you backed off the throttle some. It does this in a very patterned cycle throughout acceleration. It's like your moving the throttle up & down slightly.
At first it seemed reasonable to think the PCM needed to learn/calibrate to the truck, but I've driven it for over 150 miles and the surging is not getting any better at all. I took it back to the shop and now they're telling me that the diagnostics show EGR valve is going nuts (opening & closing) and they "believe" an EGR cooler leak is the cause. I strongly disagree with this diagnosis because it's not blowing white smoke and not using any coolant. Plus, remember, it was running perfectly when I took it in, so it would be too coincidental for the EGR cooler to happen to spring a leak right at the same time this work was done.
The shop will be doing some tests to see if they find the EGR cooler leaking today. I'll be taking it somewhere else if that's what they say and I'm hoping the gurus here might be able to point me in a more believable direction.