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Bryanluster1 · 02-07-2019, **(Subject: RPM fluctuations )**

I am experiencing RPM fluctuations at idle. Not really bad spikes but run between 761 to 771 or it’ll fluctuate rapidly between numbers. What could be the reasons behind this? It doesn’t run off after I shut motor down. 04 ISX 871 EGR

Chamberpains · 02-07-2019, **(Subject: RPM fluctuations )**

O4 is not a cm871 its a cm870. And that kind of 10 rpm fluctuating is normal. My 06 does the exact same thing. But if your paranoid, check your actuators, run the over head, perform an injector bubble test, check and rebuild your IFSM if necessary, remove your fuel pump and ensure its in good condition and change your fuel filters. This may smooth it out some.

Bryanluster1 · 02-07-2019, **(Subject: RPM fluctuations )**

(02-07-2019 )Chamberpains Wrote: O4 is not a cm871 its a cm870. And that kind of 10 rpm fluctuating is normal. My 06 does the exact same thing. But if your paranoid, check your actuators, run the over head, perform an injector bubble test, check and rebuild your IFSM if necessary, remove your fuel pump and ensure its in good condition and change your fuel filters. This may smooth it out some.

I thought mine was an 871 cause the way the entake goes up and wraps around top of motor from off the drivers side. When did the 871’s come out.? 2008? I just read this ok I have a 870 and it doesn’t do much between the rpm’s.

MBlazevic · 02-07-2019, **(Subject: RPM fluctuations )**

Mine does same thing it is 06 I think it’s normal on these CM870.. Mine was doing it bad after demandate but after I replaced injectors it quit now it will spike up just little bit but nothing concerning.. Just keep on truckin..

Nilao · 02-07-2019, **(Subject: RPM fluctuations )**

Mine (2010 871) will bounce around 20 rpm...nothing to get worried about.

Rawze · 02-08-2019, **(Subject: RPM fluctuations )**

(02-07-2019 )Bryanluster1 Wrote:
(02-07-2019 )Chamberpains Wrote: O4 is not a cm871 its a cm870. And that kind of 10 rpm fluctuating is normal. My 06 does the exact same thing. But if your paranoid, check your actuators, run the over head, perform an injector bubble test, check and rebuild your IFSM if necessary, remove your fuel pump and ensure its in good condition and change your fuel filters. This may smooth it out some.

I thought mine was an 871 cause the way the entake goes up and wraps around top of motor from off the drivers side. When did the 871’s come out.? 2008? I just read this ok I have a 870 and it doesn’t do much between the rpm’s.

CM870 is EGR only.
CM871 has EGR + DPF/regen system.

Bryanluster1 · 02-08-2019, **(Subject: RPM fluctuations )**

Got it thanks for clarifying for me!