Cummins ISX CM871 Regen Temps Question

Check the ECM calibration version. Most calibrations are version 43 or higher by now. Version 42 was a big one that dealt specifically with 1691 being generated falsely.

 

I cannot get a good regen so I just hooked up to my Insite to monitor during a parked regen and got some bad readings according to you. Everything you listed was within parameters except;

Percent load was 5 with a low of 4 and a high of 11.

Turbo charger speed was high at 59344 with a low of 54719 and a high of 62219

Most notably my dosing command stayed in the closed position the entire time which makes sense since my DOC intake temp never got above 485. This is not the 525-550 needed to activate the doser. DPF intake temp never got above 451 which goes without saying. So it appears my engine cannot generate the high temps necessary during catalyst warmup to activate dosing. You mentioned the turbo vanes causing this. Is there anything else I should also check and does the high turbo speed I am getting have anything to do with it? I recently replaced my turbo mounting gasket because it blew out and I suspect my exhaust manifold gasket is also bad based on the sound. I also have very little engine braking any more. If back pressure is escaping through a bad gasket will that not prevent the turbo vanes from building the required back pressure necessary to reach the proper temperature? In fact, could not back pressure escaping through a bad gasket cause the abnormally high turbo RPMs?

 

Where can I get the latest calibrations and how do you upload them?

 

Your problems may be a result of other things,...I have seen these scenario's before. I know the ISX very well, so don't take this lightly...

First of all, here are some reference points to check for when everything is actually running right, an EGR tuneup has been performed, there are no coolant leak problems, and there is a brand new doser injector...

A) A forced regen will take approximately 40 minutes. It will cycle through 6 stages during this 40 minute period. If the Regen cycle takes longer than this, something else is still wrong.

b) During a forced regen cycle, The DOC will get to about 550F, and the doser will activate, first, usually in short intervals, then come on solid. If everythig is working very well, the inlet tamp of the DPF will climb rapidly to 1000+F (within a couple minute or so). If it climbs slowly, say over the coarse of 8+ minutes, its still probably ok, but not that healthy (exh. leak, EGR leak, turbo out of cal., DOC ash buildup, crack, etc.).

c) When the inlet temp is 1000+F, if the doer shuts off, then stays off, and the temp falls off to 500+F early on in the regen cycle, this is usually a very good sign. What usually has happened, is that the DPF was cleaned quickly, and the regen cycle will just run out the rest of its 6 cycles without the doser at that point.

d) Anything above about 2.5-3.0 hpa on the DPF, and it is going to lower fuel mileage for the engine and is not good. If after a forced regen, the hpa is still above this range, it is cheaper to clean the DPF/DOC out than to send the truck down the road with its lowered fuel mileage.

e) I have seen a new doser injector clean out DPF's that had readings of 4,7,and even 9+ down to 0.8, 1.2, 1.1 before within a single cleaning cycle when everything is right and a new doer was installed.

Most of the time, it is in fact the doser, combined with the lack of an EGR tuneup. Doser injectors only last 250k miles, then clog up. Cleaning them usually only improves the regen cycle but does not cure the problems long term. Replacing them every 250k miles during a tuneup will always keep the DPF from giving problems, assuming there are no other related problems like a cracked DOC/DPF, no EGR, EGR cooler, excess soot problems, etc.

Typical DOC/DPF lifespan when kept healthy is about 700-800K miles where ash itself will cause a permanent 3.0+ hpa reading. At this point, it must be removed and cleaned to prevent fuel mileage losses on the engine. If there is ash buildup before this mileage range, then it was likely caused by oil-consumption, coolant consumption, or excess addatives being put into fuel system.

After the engine gets 250+k miles on it, the entire EGR system starts to deteriate, causing a 'Runnaway Effect' problem of soot. 90% of the engines I have solved DPF/DOC problems on were in fact caused by the EGR system caught in this runnaway-effect cycle, where nothing on the engine seems to act quite right, yet there are little or no faults. Rapacing a component here and there sometimes seems to solve it, but it comes back in short order, making most mechanics 'chase their tail', you might say. Insite, the enging itself, and other DIAG software will only confuse the situation further, because it cannot detect this runnaway soot problem. Performing an EGR tuneup will stop this.

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Here is how to stop it in its tracks, assuming here that there are no problems with the intercooler, engine timing, or other outside influences...

This is a repost from helping an Owner-op on another thread...


Determine the health of these systems and see what needs to be done...

<> EGR cooler, make sure it is not leaking, and has less than 600k miles on it. Above 600k miles, it will become restricted and cause many EGR and Turbo problems if it is not cleaned out or replaced.

<> EGR piping behind the engine. The flex hose on the back side of the engine can easily get a hole in it, or beciome daamaged from heat. Check it, and the joint behind the EGR cooler, to ensure they are in fact in good shape.

The Very Important, EGR tuneup...
<>Determine/Remove the soot buildup in the EGR system: Remove the IMAP sensor from the intake manifold. Very easy to do, takes less than a minute. If it is buried in soot, and it will be, at 250k+ miles, it is, at the very least, costing you fuel mileage by now, or at its worst, causing turbo problems, power loss, hesitation in the acelerator, and/or excess soot problems. You will get turbo actuator alarms long before you get alarms for this sensor being cloged. Many mechanics are fooled by this, chasing ghost problems in the much more expensive components like the turbo, egr valve, etc. I have the Insite/ Fault tree software. On its best dsays, it is only about 30% acurate in dealing with these type of ptroblems. The IMAP sensor, most of the time, can simply be cleaned using a dry toothbrush and NO chemicals. This one sensor has actually put many O/o's out of buisness. I have witnessed trucks go from 4-mpg to 8-mpg, just from cleaning it. Asuming it was in fact covered in soot, you will need several cans of 'Carb and Choke' cleaner. NOT 'Brake cleaner'!!!. Brake cleaner turns everything into a soot magnet. You will have to remove the intake manifold, Venturi (egr mixer) pipe, and Delta-P crossover tubes, washing them out, to bring back the engine's full fuel mileage potential and New-running glory. The Delta-P (EGR Differential Pressure Sensor), if it is the origional from the factory (painted red), or it has more than 250k miles on it, will have to be replaced. It cannot be cleaned properly without it giving false readings afterards. As this sensor clogs up, it causes EGR valve and EGR actuator alarms and problems, power loss, fuel mileage loss, and 'turbo-coughig' problems, quite often without ever throwing a code for the sensor.

<>Clean/Replace Exhaust Manifold Backpressure sensor: This sensor usually lasts 400-600+k miles before giving problems. It can usually be just simply cleaned, along with its feeder tube, comming off the exhaust manifold. If it is going bad, the turbo will act up. Symptoms can be of,...Turbo-coughing, turbo-lag, actuator alarms, turbo overspin alarms, and/or even turbo inlet temperature alarms. This sensor can actually kill a turbocharger over time, and/or can cause a cracked head or gaskets from excess head pressures generted by the turbo acting up. This sensor can be cheked with Insite to see if is reading correctly if it is in question, but its a cheap sensor, so just replace it if its suspect.

<> The After-treatment injector (doser injector): It operates similar to a spray-can nozzle and is located at the turbo exhaust outlet. It is easy to inspect by simply removng the 2 exhaust clamps on either side of it and looking down into the pipe. They start clogging up at 250k+ miles like clockwork, even on engines that run well and have never been idled, causing many DPF and Regen problems when they do. They are easy to change, but only if your willing to drain your coolant into some buckets first (that kinda sucks). Yes it can be cleaned, and that helps the DPF a lot, but NO, most of the time, after cleaning it, will it last very long afterwards. It also costs you fuel and can leak coolant directly into your DPF as they go bad or fail. Not worth the risk of cleaning it if u ask me. The doser injector is also a money-maker for most of the dealers. They will almost always go straight for the DOC/DPF when you visit them, ignoring the injector because of the all-to-typical 'DOC/DPF Face-Pluged alarm' that is thrown by the engine, when there is little or nothing much wrong. The engine likes to throw this code waay too aesily, and many O/o's fall victim to it when they visit the repair shop, many times, repeatedly, before the actual, more minor problem is found.

<> DPF, Visual: Look for signs to see if it has been removed/replaced. If it HAS, this is a red flag. The DPF on a cummins is big enough to sustain a healthy exhaust flow for about 700k+ miles, where ASH, not soot or coolant, will finally cause it to read above 3.0hpa on a constant basis (above 3.0 costs fuel mileage). The only exception to this is if it gets cracked/damaged due to excess road stress or being impacted by road debris (not very common but can happen). Why then is it so common for it to fail or be replaced/cleaned before this mileage range?,...Outside problems, #1 being the after-treatment injector going bad, then second, a poorly running engine that produces a lot of excess soot, or a bad EGR cooler plugging it up with coolant. ALL of witch can be avoided, with good maintenence practices, long before it kills the DOC/DPF. Removing the DOC/DPF should only be a LAST-RESORT type item when everything else has been done to avoid it, and it is the only thing left, after replacing the injector/sensors with a new ones and force-regening it to determine its actual hpa.

To sum all this up,...

every 250-300k miles,...
Remove and clean the IMAP sensor, Intake manifold, Venturi pipe, Delta-P crossover tubes, Exh. backpressure sensor and feeder tube, and EGR temp. sensor.

Just replace the Delta-P sensor and After-Treatment injector. Then perform a DPF 'Forced Regen', ensuring the DPF is still below 3.0 hpa (it will almost always be below 2.0 hpa after a good cleaning by the regen with new after-treatment injector).

cost?,...$300-400 for after-treatment inj., $150-200 for Delta-P, 3 five-gallon buckets for holding your coolant, and a day of downtime, while drinking beer and getting very dirty. If you can change a spark plug for your car or lawn mower, then you are very likely capable of these things as well.

Gains?,...Better fuel mileage, less downtime, less problems, increased engine longevity more than outweighing the costs or headache of doing it.

Can a shop do this for you?,...well,...possibly for a few thousand bucks. Not worth taking it to them if u ask me.

Ignoring it,...Countless truck problems, downtime, and thousands uppon thousands in repair bills by the truck steeler(dealer) because they will blame the bigger ticket items either out of ignorance, or for extra profit. Most will laugh at you for mentioning simply cleaning these things instead of replacing them as well.


Maybe this helps someone out there who is already having issues,...Rawze.

 

Rawze - Are you now or have you ever been a trained mechanic? Or did you learn all this stuff the hard way?

Regarding all of the items above you mentioned that needed to be clean can you describe how you clean each of these items? Do I need to soak them in carb cleaner or what do I do?

 

Sounds like your turbo is on its way out, check your turbo actuator position, it's should be 89% or higher. I've had them at 87% and just a tad shy of 500 degrees and not light up.