intermittent spn 0102 fmi 18 cm871

[jgriffin812]

howdy yall, I have a 2009 Pete with a cm871 1.47 million miles. I am getting an intermittent low boost code, I have an aftermarket boost and pyro gauge that shows low boost, I haven't seen over 21psi since the code first showed up. When the code pops up my egts get very high 1200+ and my boost doesn't get over 17 to 18 usually lower. I can hear almost a screech from what sounds like the EGR. after a bit the screech will go away and then it builds up to 21 psi. My inline 6 box didn't want to connect to my truck the last time i tried it but my nexlink code reader has some live data if needed. any other info needed let me know and i will try to get it as soon as possible. thanks for your help.

[Rawze]

CM871 should be making 36-37 psi boost in a hard sustained pull.

check CAC and other related systems for reason why such low boost.

[jgriffin812]

I had some small leaks at the CAC boots, those were replaced, no more leaks there. i changed the imap sensor about a month ago when the problem started. I recently, after the code popped up, had the exhaust manifold off to change out 2 broken bolts on cylinder 1. My thought was i was loosing pressure before the turbo so it had low boost. not the case same problem after, but at least I have no broken manifold bolts and i was able to drill out and tap the egt sensor with the manifold off to make sure it was clean and also blow through the back pressure tube that was clear. when the code is active I have boost at idle so it makes it easier to check for leaks, when I spray the CAC itself with my soap water mix i cant see any bubbles. I've sprayed the soapy water around the egr crossover as best as I can but access is limited. thanks again.

[Rawze]

Also, if the engine is de-mandated (deleted) then copy the program out and e-mail it to me for a proper review of what someone might have done in there.

is the CAC an OEM unit?.. or an after-garbage brand?... most after-market brand of CAC are very restrictive and can cause boost problems.

[jgriffin812]

Unfortunately it is mandated, has the "upgraded" dpf not sure what year the recall was I've only had the truck 3 years or so, esn 79290289 cpl 2733. the cac says paccar close to the boots. I would love to de mandate it but i need to fix the issues first, i think.

[Rawze]

Check the EGR soft boot that is on the back side of the head behind cylinder #6 exhaust side. It tends to burn out a hole between the head and the boot, making it hard to spot when they get old and then cause low boost.

Also take the hard pipe on the drivers side where it comes off the top of the EGR valve (intake side at cylinder #6 area) , and give it a good yank. They rust out internally there, and then it lifts off the egr valve slightly when under higher boost, because it has rusted apart internally.

[jgriffin812]

Okay, I changed to crossover tube behind the engine in April or may of 2023, last time I took the egr off was earlier this year nothing seemed off or rusted, but ill go out and check those again today and get back to you.

[jgriffin812]

Okay so this was a bit loose, looks like I didn't tighten it down enough last time? We shall see if it stays away and what my bost gets up to when I take her back out.

[jgriffin812]

That still doesn't explain the boost pressure at idle sometimes does it?