Cylinder Contribution Test Failed?

[nexttimeforsure]

Earlier this week I had my 99 F250 Super Duty (7.3 diesel) to the Ford garage for diagnostic scoping. The truck has about 200,000 km (120,000 mi) and was idling and running rough. The technician found a Diablosport performance chip in the PCM - removed it and reset everything to factory settings. At the end of the day the truck runs beautifully - the idle is smooth and it runs out great.

The technician tells me that at the start of his scoping, AND after removing the chip and restoring to factory settings there was a CCT failure for cylinders 4 and 5. He recommends replacing injectors 4 and 5.

Here are my questions...
1. If I have an issue with the function of 2 injectors, shouldn't the truck at least be running rough?
2. Is there a problem driving the truck "as-is" if I assume that injectors 4 and 5 are malfunctioning?
3. Could something else other than injectors cause a CCT failure?

Thanks in advance all!

[HVAC SuperTech]

Well, sometimes you cannot tell if there is an injector falure while driving it. it may be intermittant and it may not fail at all times. slightly press on the throttle pedal to bring the rpms up to about 1200. do you hear a miss or a studder? lots of times the injector problem will show itself there.

theres not a real problem with driving the truck like that. I had 4 out on mine and it drove ok. just down on power when pulling a huge hill with a load behind it, EGTS go up too, but with you being stock, you should be ok in the egt dept.

I dont think CCT faiures can be comming from anything else but injector issues. it could be something with the Under valve cover harness thats causing those injectors to fail. the power for the injectors comes from this harness. sometimes they can become scuffed, and broken. or the clips that attach directly to the injectors can come off. but not really likely they fell off if the trucks not had any work done to it.

[Highwaywrench]

I recently spoke with a guy who has worked for ford, strictly on diesel pickups for 20+ years. He told me this:

The buzz test is accurate, however, the cylinder contribution test has been faulty since day 1, and so far nobody has built a scanner that makes it accurate.

I found that hard to believe, so I did a CCT. Well, number 3 failed. So, because I had it apart anyway, we swapped the IDM. Did another CCT. This time #2 failed. So we swapped in ANOTHER IDM, and this time #6 failed.

However, all three IDM's passed the buzz test. And the truck wasn't missing with any of the three. ( It had other issues )

Just food for thought

[Dave]

Do you have the black or gray cps in the truck?

[billelf123]

Originally Posted by Highwaywrench

I recently spoke with a guy who has worked for ford, strictly on diesel pickups for 20+ years. He told me this:

The buzz test is accurate, however, the cylinder contribution test has been faulty since day 1, and so far nobody has built a scanner that makes it accurate.

I found that hard to believe, so I did a CCT. Well, number 3 failed. So, because I had it apart anyway, we swapped the IDM. Did another CCT. This time #2 failed. So we swapped in ANOTHER IDM, and this time #6 failed.

However, all three IDM's passed the buzz test. And the truck wasn't missing with any of the three. ( It had other issues )

Just food for thought

Nice response! This is exactly why I became a member of this forum

[Dave]

Originally Posted by Highwaywrench

I recently spoke with a guy who has worked for ford, strictly on diesel pickups for 20+ years. He told me this:

The buzz test is accurate, however, the cylinder contribution test has been faulty since day 1, and so far nobody has built a scanner that makes it accurate.

I found that hard to believe, so I did a CCT. Well, number 3 failed. So, because I had it apart anyway, we swapped the IDM. Did another CCT. This time #2 failed. So we swapped in ANOTHER IDM, and this time #6 failed.

However, all three IDM's passed the buzz test. And the truck wasn't missing with any of the three. ( It had other issues )

Just food for thought

This is the first if have heard of the CCT being innacurate. Unless there was a gray CPS in the truck

[billelf123]

Originally Posted by Dave

This is the first if have heard of the CCT being innacurate. Unless there was a gray CPS in the truck

I am listening!

[SCUFFY828]

i will say this , i believe the injector buzz test is as accurate as it gets , as far as cylinder contribution test is concerned it is fairly accurate but can be a little misleading but id say 85% correct, with that said , if the cylinders 4 and 5 are showing bad on cct , doesnt mean injector is bad , any component can cause cct to fail injector , valve problem, low compression ,etc. when a cct is done , especially with 200,000 miles , a compression test needs to be the next step,and done on at least the side the skip is on to get a accurate reading of what is goin on inside the engine if compression is good on the engine , then address a injector issue , most of the time a cct test doesnt fail if the engine isnt skipping so i will have to disagree with you can have a problem with a injector and the engine run fine , if the engine is running fine and has good power then why even address it at all , in this case i would want to have it shown to me that those cylinders failed before buying any parts if there were any question at all

---

Last edited by SCUFFY828 : 07-03-2009 at 09:33 AM.

[billelf123]

Originally Posted by SCUFFY828

i will say this , i believe the injector buzz test is as accurate as it gets , as far as cylinder contribution test is concerned it is fairly accurate but can be a little misleading but id say 85% correct, with that said , if the cylinders 4 and 5 are showing bad on cct , doesnt mean injector is bad , any component can cause cct to fail injector , valve problem, low compression ,etc. when a cct is done , especially with 200,000 miles , a compression test needs to be the next step,and done on at least the side the skip is on to get a accurate reading of what is goin on inside the engine if compression is good on the engine , then address a injector issue , most of the time a cct test doesnt fail if the engine isnt skipping so i will have to disagree with you can have a problem with a injector and the engine run fine , if the engine is running fine and has good power then why even address it at all , in this case i would want to have it shown to me that those cylinders failed before buying any parts if there were any question at all

Good stuff!

[nexttimeforsure]

For Dave: The truck currently has a grey CPS in place. Does that affect any decision making?

Other notes - the truck currently has 120,000 miles (not 200,000 as was quoted earlier). It starts promptly hot and cold, and it uses no oil to speak of. This morning I had my son start it cold while I sat by the tail pipe. There was a split second tiny puff of blue, and then it went colorless.

After speaking with the technician again this morning and both of us listening to it run at different RPM's we have elected to leave it alone for now.

Thanks for the great responses. Feel free to add more if anything comes to mind!