Rough running at idle, after 2 hour drive...

[RoReRi]

I have just recently gotten some Stage 1 type injectors, within the last 3 months. Lately it’s been running rough and I just passed it off as my imagination or it was just cold and damp.
Not so…
I have narrowed it down. I ran an AE, cylinder contribution test right after a three hour hard drive and it showed a couple of bad holes, #2 & 8, and I did it again same drive and it showed #3 & 7 bad. I do this every time I make a several hour drive, and have done it about 5 times. Every time I do the test, I get different injectors...
AND
Every time I let it cool down for an hour or so, crank it up and let the oil heat up to 160 degrees. The AE Cylinder contribution test will not run at a temp lower than that.
Guess what? Every time I let it cool down No problem cylinders shown, test passes.

My guess is that there is a problem with the injector’s tolerance somewhere? The heat expands the innards somewhat and gives problems.

I have changed out both Valve cover gaskets; (burnt pins) fixed the truck’s harness with new pigtails and installed 4 new UVC wiring harnesses. So all the wiring looks good

What are your thoughts on this??? I am stumped.

 

[95_stroker]

Who built your injectors?

 

[RoReRi]

I really don't want to say right now, until I find out what is really wrong...

RoReRi

 

[JOAT]

You can run the tests below 160* but you need to trick the PCM. Disconnect the EOT sensor and jumper across the connector a resistor, try 2k Ohm (I'm not positive on 96 but think that will work). May run a little rough tho as the PCM will be setting the injection for a hot engine, but it should allow you to run the tests.

BTW, try the tests with the chip removed too. I sometimes get funky results with the EASE if I run it on a truck with a chip.

When did you change the oil last? Aeration could cause weird injector issues after a long run...

 

[RoReRi]

You can run the tests below 160* but you need to trick the PCM. Disconnect the EOT sensor and jumper across the connector a resistor, try 2k Ohm (I'm not positive on 96 but think that will work). May run a little rough tho as the PCM will be setting the injection for a hot engine, but it should allow you to run the tests.

BTW, try the tests with the chip removed too. I sometimes get funky results with the EASE if I run it on a truck with a chip.

When did you change the oil last? Aeration could cause weird injector issues after a long run...

It seems like the test will run just fine once the engine has cooled down for an hour or so, its just when hot that I get the problems. If the engine oil has cooled below 160*F, I have to run the truck just enough to get past 160* and then it will run....and pass. But let me run the truck for an hour or so to really bring it up to operating temps, thats when I get the failures on the Cylinder Contribution tests...And these failures are wierd, on different injectors just about every time..

There is no chip to speak of, the PCM was just reflashed by Jody to an updated burn with an extra 40 hp.

I have about 1500 miles on this oil change.

 

[JOAT]

Strange that it's only when really heat soaked. I wonder if it could be a hot problem with the IDM?

 

[RoReRi]

Strange that it's only when really heat soaked. I wonder if it could be a hot problem with the IDM?

Hmmmm... I have gotten a couple of IDM errors in the past several months, but only two.
Maybe next time I've returned from a several hour trip, I'll test hot then test after I unload a CO2 fire extingusher on the IDM.
That'll cool her down... maybe not unload, just make sure its not hot anymore...

RoReRi

 

[KansasDiesel]

Are you still running WVO? Are the test while running WVO. Not saying this is a contributing issue. But if different injectors or getting carbon build up then burning off and the next time different injectors have build-up and the others are clean.

I have a similer problem but only at idle and intermittent. My AE test showed 3 cylinders a problem..
But I haven't checked it after different trips.

 

[RoReRi]

This is after a couple of hour trip, and I purge from WVO to Diesel about 35 miles before I get home, so I have run about two gallons of fuel through the system.

I have tried cooling down the IDM, no change in symptoms, other than it is a different injector all the time. But mostly its #5 #8 #7. Other than that it all across the board.

I clear out all codes before I start the tests every time.

I haven't checked when cold, haven't "tricked" the system into thinking the oil was up to temp. But with just a short drive to the store to pick up a gallon of milk, about a 4 mile round trip. The engine oil is up to temp and everything tests good...

I am befuddled, and confused. What/where do I check next? Or do I have bad injectors like I'm thinking???

thanks !!!

RoReRi

 

[action4478]

I f it were me I would look at the IPR orings....Its a cheap test, about $30.00


This is from D.M.'s page

If the concern is a jerky, irratic idle when hot, unplug the ICP sensor (will set a code, causes the PCM to default to a pre-selected IPR duty cycle) to see if it the idle stabilizes. If it does, check the ICP voltage with a scan tool or breakout box at pins 87 to 91 with the sensor plugged in and the key on/engine off. It should be .20-.25 volts. If the base ICP voltage is within specs, replace the IPR; If not, replace the ICP and retest.