Hey guys,
I'm looking for some opinions on this strange issue with my engine. The truck runs like a champ all day long every day. It starts right up, idles just fine, and sounds normal. However, when it's in gear and EOT is up to normal, I can lightly nudge the throttle and then engine drops rpm and starts shaking and knocking like its misfiring until it eventually dies a few seconds later. If I pop the throttle while it's doing that (say, up to 1500 rpm), then let it settle back down, it idles fine again.

I can reproduce this scenario almost every time. This is the only sequence that makes the engine run strange - plenty of power otherwise. I'm not entirely clear how this engine works, with the oil pump and the phasers, since I've had it less than a year and came from a 7.3 Powerstroke before it. But i figure there's a slight drop in oil pressure when I nudge the throttle, and this might affect the cam phasers somewhat. Then when I pop the throttle, the oil pressure increases enough to allow the phasers to adjust and settle back in. I've watched a ton of videos and read a bunch of forum posts about phasers and understand the basics of how they work. Nothing I've seen so far has been quite like my issue.

Does that make sense to anyone? Am I on the right track at least? I'm trying to plan for repairs and want to understand if I need to replace the oil pump or the phasers (or both maybe).

Thanks for any help...
2007 5.4L

 

Mellings just came out with a new oil pump for the 5.4 that has higher volume. To track down VCT solenoid, oil pressure issues drop the oil, put some thicker stuff in there and see if it does it again. it it does, then you're probably having return spring failure in the phasers themselves it sounds to me. There's a few non VCT issues to check as well however (spark plugs, coils, etc.)

 

I saw a vid on the high volume oil pump a while back: I definitely plan on doing that if I ever have to remove the front cover. I'm running 5w30 oil on a fresh oil change, but that doesn't affect the issue. I don't get any codes when it happens either. I'm planning on a plug change since I don't know when the last one was done. I'm just not the type to throw parts and money at a problem without knowing what's causing it. No codes seems strange to me though.

Another question about the thicker oil though: Is 5w30 thick enough to work as a VCT/oil pressure test? I have a couple gallons of new Rotella 15w40 left over form my 7.3 that I don't have a good use for. I was thinking phaser return springs as well initially, but felt some more opinions were worth it before I start sliding plastic.

 

5w30 is a good operating weight for the 5.4, but not really enough for diagnostics. It can get expensive, but better to drop the oil a couple times than tear into the engine looking for problems. 10w40 is what i used to diagnose mine, but i would imagine 15w would be fine as long as you drop it and replace with 5w30 after diagnostics.

Another thing to try is unplugging the VCT solenoids which will effectively shut off the VCT completely. It should stay at dead center this way, which can tell you if you have a phaser problem as well.

 

Thank you for the info. I'll try both this weekend while I'm on call. I'm stuck at the house and can't go anywhere anyway. Sucks that I just changed the oil about 500 miles ago though. I'll do the VCT test first.

 

if you just dropped oil in it, i would definitely try the solenoids first lol. if it runs fine with the solenoids unplugged (you will get a CEL with them unplugged just an fyi) you're looking at oil pump, oil galleries, and the solenoids themselves. if it still runs weird then that will be indicitave of the phaser return spring/phasers themselves or their oil channels in the top end.

 

take throttle body off engine to clean it. use throttle body cleaner , use maf cleaner on maf . Look at your foam seal around filter housing . What codes are you getting .

 

 

If you have android phone--- get bluetooth reader and 5 dollar app torque pro and watch realtime data .

 

That's a good idea. I have an iPhone but I'm looking at this thing for $20 that looks like it can give me real-time readings.