My truck at idle feels like it's missing a cylinder because the whole damn truck is rocking. I've had this truck almost two years, so I know this isn't normal. The only thing that changed was I installed a DP tuner last sunday, and this started happening I guess yesterday. I try to keep it on the 60tow, but have run it on the 80 eco and 120 smoke.

I put my Predator on it to check for codes, but nothing came up. The truck has just about 195,000 miles on it. Also, you can make out a more pronounced knock every 5-6 seconds or so, which is why I'm thinking it's a fuel problem, and not something brought on by the tuner. Jody does nothing but great work so I'm pretty damn sure it's my truck.

Is there anything I should be looking for? Maybe one of my injectors is starting to take a crap on me? Maybe I should just run it down to about empty and dump 1 or 2 cans of seafoam in the tank??

Thanks for the advice- I'd prefer not to take it to the stealership....

 

BUMP

MY $.02 since I do they electrickyiar stuff at work:

I am thinking it has something to do with the install, But I ain't qualified to really comment. Problem did occur after a install and there has been trouble cleaning the contact pins in the past

 

Oil level and quality has caused some problems around here lately. If you think it could be tuner related, just uninstall and try it.

 

Did you by any chance test the new Tuner with a hard run ?....

May have finished off a ready to go Injector o ring ....Check the ICP with a scanner & IPR DC % ,,,or a guage set to isolate each of the heads & the HPOP ...

 

I'd go ahead and pull the chip too, just to see. Then you may need to hook it up to a scantool and datalog if the problem persists.

 

I'd follow Mike's advice. Remove the chip first to rule that out. Then get a scanner. You can do an injector buzz test and some data logging to narrow it down from there.

 

I did remove the tuner (just disconnected the control head from the wire) and it still runs kinda goofy. I guess tomorrow I should bring it by the dealership for a contribution or buzz test? Again, I'm getting no SES light or codes coming up on my Predator scanner, so I'm kinda stumped.

What kinda numbers should I be looking for on the IPC or IPR?

 

Remove the chip from the PCM and then proceed. DP stock tunes are not stock tunes.

 

UPDATE**** I hooked up the Predator just a while ago while idling, and it showed #6 and #8 cylinder at in between 2.7 and up to 4.3%. As soon as I barely stepped on the throttle, they went back to 0% What does that mean??

FYI- I had the Predator on this before at the 60hp setting. I also have my homemade cackle cure and I'm wondering why the #6&8 cyls are effected, could it just be coincidence?

 

See my last post. The velocity test on the predator is probably like the AE and will show zero as soon as you go above idle. I believe this is due to sampling rates.

 

Gotch Mike, thanks. But then what- if it runs fine, I guess I call Jody?

 

UPDATE #2- I took the tuner off the PCM completely, and it still shows #6 and #8 cylinder differential of about 1.2-2.5% (being back to stock).

I took it to the dealership and although they didn't hook it up as the mech said my Predator scanner is basically the same thing they have, he took the time to let me know the following

- it could be the wire loom under the valve cover (but it's not running as rough as if 2 cylinders were not firing at all)
- it could be two injectors not bleeding down enough to re-fill the proper amount of fuel (is that from the tuner boosting the ICP??)
- remote possibility of loss of compression (but I don't see how with no other press loss indicators)

So basically I have to drop it off monday, and I get to worry my whole vaction about how much it's gonna cost me, because as usual this thing goes down when I have the least amount of time to work on it.....

At least I get the "military discount" 'cause the service writers son and daughter in law are both Jarheads like me. I think I'll still need the vaseline though.....

 

Did they check poppet clearence or rule out Injector O rings ...( can be done visually)..Or a guage to isolate ICP on each head ,,,,,,,?

 

Nothing was done at the time I stopped in, but I'm trying to gather ideas or suggestions to have them look at to save me some man-hours and CA$H.

 

It sounds like Rick may be on the right track, but 6 & 8 going out together does sound like a fuel issue more than 2 injectors or o-rings next to each other. Can you monitor ICP with the predator? Since ICP & IPR usually throw their own codes and UVCH wires usually give you an IDM code, Injectors, o-rings, poppet valve all sound like logical possibilities.

Here's some info from the manual on ICP & IPR. Let me know if you need more.
DC1 CHECK FOR BIASED ICP SENSOR
• Warm up engine.
• Turn off engine for one minute.
• KOEO.
• Refer to Section 2 , Diagnostic Methods, Parameter Identification (PID), Selecting Parameter Identification (PID).
• Select PIDs ICP and ICP V.
Does ICP PID read greater than 0 kPa (0 psi) or ICP V PID read greater than 0.30 V?
Yes GO to DC2 .
No GO to Symptom Chart 7.


Output Functions
Injection Pressure Regulator (IPR) — A variable position valve that controls injection control pressure. The powertrain control module (PCM) uses many input variables to determine the desired injection control pressure.
Battery voltage is supplied to the IPR when the ignition key is in the ON position. Valve position is controlled by switching the output signal circuit to ground inside the PCM. ON/OFF time is modulated from 0 to 50% dependent upon the desired injection control pressure.
Detection/Management
An open or shorted to ground control circuit can be detected by an on demand output circuit check performed during the KOEO test. When the starter is engaged and the engine fails to start, the IPR command will increase toward its maximum until the engine starts. The normal range for the IPR at idle is between 8-16%. An above 16% range indicates high effort to achieve idle. A below 8% indicates low effort to achieve idle.
The PCM is capable of detecting whether desired injection control pressure is equal to measured injection control pressure while the engine is running. If the measured injection control pressure does not reasonably compare to the desired injection control pressure the PCM ignores the measured ICP sensor signal and attempts to control the engine with the desired value. (If the problem was in the sensor circuit this strategy causes little performance deterioration. If the problem is in the control circuit, engine performance will probably still be unsatisfactory).
An injection control pressure step test, in which the PCM commands and then measures specific preprogrammed pressures is performed during the KOER test.
The engine will not operate with an IPR circuit that is not functioning.