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What is that clicking sound every 3 seconds or so that I hear in the background of your PERDEL test?
Truck has a smooth idle from the sound.
It has one of those aftermarket hour meters installed. I’ve gotten so used to it I had to listen to see what it was….
Originally Posted by BWST
These tests are good to have in your pocket now. Nice strong buzz test. That lines up with the rig running ok at idle or low power settings, right? The low power/miss has been occurring at higher loads that these tests may not see. Confirming no codes after the buzz test?
Yeah it runs fine at idle and lower power. It does fairly decent at mid to high throttle but the miss starts to show up at higher throttle. Not much but a little bit. Now if you stick a trailer behind it it gets noticeable quickly especially pulling hills. But no no codes that relate to the contribution test.
Maybe keep one eye on the fuel pressure gauge when towing hard - wondering if 1-2 cylinders can miss when fuel pressure is borderline (under 45psi).
Can a CPS cause a miss and not trigger a code? Trying to brainstorm other possible causes.
If the signal was somehow delayed a ms or 2. Not sure what would slow down an electrical signal though. From what I've read the CPS is sending a 12v burst every time it picks up the "marks" on the cam gear with a shorter or longer burst at the #1 tdc. So even an increase in resistance would only drop current in turn voltage too a certain amount, the PCM should still get the signal in the same speed.
A bent pushrod or sticking valve can cause a miss. I would kind of expect those to show themselves at idle too though, but anything is possible. Maybe the valve would only gang when under load and temps are higher. All completely hypothetical btw.
I have been slowly picking away at trying to fix it. Trying to go on a remote haul trip with it in a week and a half so still wanting to make sure it’s good by then and have to fix a broken leaf spring also. Anyway today driving I would see as low as 37psi on the fuel side when hammering it(once it was warmed up). Usually averaged around 50-55psi driving normally. But when sitting idling it would go down to around 34-45. Very strange it varies with rpm. Voltage stays the same. I swapped the FPR spring to the black one this evening and now pressure stays low of 54 and stays around 60-62. I’m wondering if having the FRX is messing with the fuel pressures.
I did set off a new code today though. P1670. Further research shows it’s possible to be the CPS or a IDM issue…..
That fuel pump behavior sounds like you've got a weak connection somewhere along the line. A voltage drop test will give you a pass/fail for the wiring and they're simple enough to do. Here's a video explaining how to go about it.
You might have had the wrong spring in there for the FRX. Varying fuel pressure with load would be normal, if in the 54 to 62psi range you are seeing now.
That P1670 could certainly cause the miss. With the buzz test telling us the IDM is working, check the wiring/connections while wiggling for shorts/opens between the IDM and PCM. If the wiring comes up good, it might be time to send the PCM/IDM to dieseltechchatt.com for checkup/repair.
Take a look at the attached troubleshooting for P1670 for wiring checks. If you just have P1670, and not other related codes, start at FJ10:
You might have had the wrong spring in there for the FRX. Varying fuel pressure with load would be normal, if in the 54 to 62psi range you are seeing now.
That P1670 could certainly cause the miss. With the buzz test telling us the IDM is working, check the wiring/connections while wiggling for shorts/opens between the IDM and PCM. If the wiring comes up good, it might be time to send the PCM/IDM to dieseltechchatt.com for checkup/repair.
Take a look at the attached troubleshooting for P1670 for wiring checks. If you just have P1670, and not other related codes, start at FJ10:
Thanks for the attachment. That’s a pretty handy test. Im kind of leaning towards PCM/IDM issue now. With the miss at higher rpms, the engine code that points towards it, my obd reader having a really hard time staying connected to the pcm or not connecting at all and the fuel pump pressure not stay consistent sounds all like computer to me.
That fuel pump behavior sounds like you've got a weak connection somewhere along the line. A voltage drop test will give you a pass/fail for the wiring and they're simple enough to do. Here's a video explaining how to go about it.
well I did this test and got
0.7 on the positive side and 0.6 on the negative.
That would indicate a problem for sure. Considering it's on both sides of the circuit I'd start looking at main power supply. Easy stuff first, how's the terminal ends and cables look? From there I'd go to the starter relay where the main power cable hooks up and keep working down the line. It's possible this ties in with your stumbling and other symptoms. Electronics like the PCM and IDM are even more sensitive to voltage fluctuations. I was reading last light while finding that video that as little as 0.1-0.2v of drop is enough to cause problem with that kind of stuff.
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