Does anyone have any ideas about why my cat diesel runs at low rpms like it has a miss. I have changed fuel filter no help. I have used injector cleaner no help. Generator runs fine on same fuel supply and I have used over one hundred gallons of diesel (trip) Miss is still there no better no worse

tripleesignature, welcome to iRV2.com. We are glad to have you join us here and we look forward to reading of your adventures and experiences. Sorry to hear of the Cat issue. I am going to put in a short cut to the Cat Owners section of the forum so we can get you some asnwers. Good luck and keep us posted. Have a great summer.

I forgot to add it is a 2004 C7 300 HP Diesel Pusher motorhome

Hope it is not an injector. $$$$

check for broken or missing blades on the engine fan. it happened to me.

It is most likely an injector problem. When an ijector is leaking it will cause a miss at idle.

Try someplace like this...

http://www.accurateis.com/

From a CAT site re: the C7 engine and it's injectors...

Improved HEUI Fuel Injectors
The Cat C7 has proven high-pressure, direct injection fuel system electronically monitors operator demands and sensors optimize engine performance.
Hydraulically actuated electronic fuel injection (or HEUI™) is a Caterpillar-exclusive technology with a proven track record built by millions of engine hours. The refined HEUI design delivers multiple microbursts of fuel during the engine’s compression stroke, precisely regulating the combustion cycle. The improved HEUI design also enhances combustion and “rate shaping” of fuel delivery, which helps control engine sound and vibration levels. The HEUI system continues to offer excellent reliability because it has fewer moving parts than mechanical unit injection and requires very few adjustments, reducing maintenance costs and increasing machine availability.

Here is a link to a description of the C7 setup from an off-road CAT equipment site but I suspect it is similar if not exactly the same engine.

C7 INFO

...and yet another blurb about the CAT HEUI injection system

HEUI™ Fuel Injection System
• HEUI fuel system fully integrated with ADEM
advanced electronics
• Cross-flow cylinder head with integral fuel and oil
manifolds — completely rebuildable
• Improved cold startability (down to 0° F) — with
standard air inlet heater
• Caterpillar designed combustion technology and
performance criteria for superior fuel economy and
greater performance over a wider operating range
• Higher injection pressures for better fuel economy
and performance while meeting latest emissions
standards
• Adjustment-free HEUI fuel injector with stainless
steel sleeve for greater reliability
• HEUI oil rail integrated into cylinder head provides
high-pressure oil to power the HEUI injectors

Per Johnson CAT, they are about $450 each

Their number is (951)683-5960. I realize you are in MN but maybe give a call to your local CAT dealer. Johnson is a HD machinery dealer but they also have a truck division/shop on site to deal with on-the-road rigs including MH's. You should first bring it to a shop so they can put it "on a scope" and diagnose the source of the miss before you shell out that kind of $$$.

Just my $.02 Pesos

This is a site that provides a very good document regarding the HUEI fuel delivery system: pump, injectors, diagrams and explanations.
Here

At present my 2004 330 HP C7 engine shutters at take off and has depowered twice, but clears it self and then runs well the rest of the day. Next morning the same thing happens again; this has been going on since early June. A CAT dealer has replaced injector #1 and the fuel regulator valve (fuel line check valve) and has now ordered a second injector for cyclinder #2. Apparently, in my case, trouble shooting the problem is an expensive hard guess as even the ECM snap-shot while the shutter occurrs is not providing a specific clue. The cost of the injector replacement is included in the CAT five year warranty which ends in December. SteveG

Yes it sounds like a bad injector, or blocked feed line to an injector.

What is the likelyhood that CAT will replace all of the injectors in case your batch was defective? With two being replaced, it could be a godd enough reason for requesting all be replaced JIC.