Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Yes, all fuel trims are in closed loop. I have actually put it back into open loop several times to see if there is any change during rough idle. But there was no change.
For GM vehicles I use tech2win with a vci for diagnostics. And I use the vci with ACDelco TDS for the stock programming of modules.
What a disappointment. Programmed the TCM, updated the BCM since it wasn't updated to latest from GM, drove the truck......... still runs amazing and then triggers. EVERY time it triggers, it's on deceleration. And it doesn't matter if the brake is applied or not, because I was wondering that and tested it out. I'm going to check the oil pressure, as suggested. I noticed a mild grinding type sound when this is acting up. I will also check and see if that sound is engine or transmission related when I get it acting up again.
So bummed over this. Gotta get it done and back to the owner!
Ok.... we may be onto something. Oil pressure cold start was around 14-16 I believe. Which seems about right to me. But I haven't had a chance to look up the spec. I'm going to retest after it cools down. Pressures would run up to around 35-40 under throttle while driving. After the truck got good and warm it was running 10psi at idle. Then dropped between 8-10 at idle. That seems low to me. But would love for someone to chime in on this make/model, as to normal range. This truck seems to really start acting up when the oil pressure gets down to 8psi.
Just to note: New oil pump from the mechanic who did the timing and phaser right before it came to me.
If you look up engine specs on FSM/Chilton/Mitchell, it should say the minimum oil pressure spec at hot idle. For Ford 5.4Ls, if they get below 13 psi, you have issues - spec is like 15 or 18. So I'm assuming that 8psi is way too low and that is your problem. Once again, find out what quality oil pump was installed. Otherwise, some research is in order for finding out what components besides bearing clearances cause oil pressure bleeding on this engine. For example, on the 5.4L, it's blown timing chain tensioner seals, oil pump, rocker arms, phasers, etc.
The problem might just be a faulty cheap exhaust cam phaser.
Another option to do is simply unplug the solenoid while running good. Then it won’t have a chance to allow the phaser to move. Then you’d basically have it narrowed down to the vvt system or oil pressure
Yes, that's a great idea. I remember doing that on the F-150 5.4L, and it would "cure" the VVT/oil pressure problem by not allowing timing to advance/retard. I believe what's happening is there is not enough oil pressure to lock the phaser/actuator back into base timing when you return to an idle when hot. So if you never leave base timing to begin with, it should not have this symptom.
Brilliant Cheryl. I have unhooked the solenoid in various scenarios. But I haven't done it prior to the issue happening and seeing if it continues to run clean. I'm a little leary to run it too much when warm now, knowing how low the oil pressure is getting. I was already skeptical, since I could hear the engine getting a little noisy when hot. But I may give that a shot today just to verify the theory.
I agree with you Joshua, that the low oil pressure is likely keeping the phaser from engaging. it seems like at 10psi and above the truck does ok until it drops below 8psi. Which would make sense with your theory.
I just got off the phone with the owner, and we are going to get the mechanic in the loop to see how everyone wants to proceed. I'll keep you all posted on how this goes. You all are awesome, and I'm greatly appreciative.
It could be that a gasket / o-ring was not installed where it should have been when installing the pick-up tube and oil pump.
It may be that the rebuilt engine had excessive bearing clearances. See if there's a TSB for low oil pressure. You might be able to purchase a high-volume oil pump for it. Check Rock Auto.
Thank you both for all of your help on this. I couldn't have finished it up without you. I hope I can pay it back some day.
Spoke with the owners mechanic yesterday when he came and picked the truck up. He will be pulling the oil pan to start from there in looking over why the oil pressure is staying so low. He was concerned about the crankshaft bearings, as he has had several with very high miles come through his shop with issues with the bearings. And this motor was put in just prior to this owner buying it several months ago. So no telling what miles this motor has on it.
One last note. When I drained oil from the pan it looked pretty clean and new. However, when I disconnected my oil gauge from above the oil filter, the oil looked very very used and dirty. Seems like it's not circulating to me. Never a good sign.
Anyhow.... This one is off my docket. So thanks again, genuinely. Today I play catch up and work on two RV leveling systems, and tomorrow I'm off to work on an International Prostar Tractor/Trailer. Never a dull moment!
The controllers I'm working on currently are for electric stabilizers. I just have the controllers in the shop. Sometimes I don't find issues with them, and they will have me come out and track the problem. But a lot of these systems have enough documentation that the RV mechanics can test and verify "voltage in, no activation, still not working. Get the electrical guy to look at it." LOL. And these can be pricey, with no parts available for many of them. So worth it for them to have me repair them. Same with the semis and heavy equipment. But more often than not, they bring me a bcm or ecm and it tests out fine on the bench. Which normally leads to them asking me to come out and trace the issue, since they are spinning their wheels (obviously not literally) with a truck that's losing the business money. Tons of wiring harness issues, and chaffing. You would thing the manufacturers would figure it out.
I'm not sure on the PM front. That definitely would be a nice feature. I'm in Florida. I'm easy to find with a quick google search..... I'm not famous and I'm not infamous. I'm just listed on google (under my business). So my info can be found that way, rather than posting it here. But definitely will buy you lunch if you are in the neighborhood on vacation.
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