Ok, had a bad exhaust gasket. Bolts broke and had to have the head pulled on the passenger side to get them drilled out. Put in a new timing chain set at the time. All new gaskets, plugs, and coil packs. Has a new battery, starter, belt, upper control arms and lower ball joints. Getting ready for a 700 mile drive to Florida pulling a trailer. Once done the truck ran like crap. Mechanic determined it was the fuel pump with only 20 pounds of pressure. So replaced the fuel pump, regulator, and filter. Runs better until a bit warm. Then startshe idling bad again. Seems ok after 2000 rpms. Lower runs bad again. Went to a different mechanic after finding loose vacuum lines that did not fix the issue. Got a code for coil pack 8. Moved the #8 plug and coil pack to 7. Basically switched them. Still intermittent code on #8. So I replaced all the fuel injectors. Still the same thing. Also changed egr valve when it was apart, oh, and the exhaust manifold itself was replaced.

The original mechanic has to fix an oil leak on the drivers side valve cover (taken off due to timing cover removal)...but I'm not sure I can get the truck to him. Runsure better with overdrive off as the rpms are higher. I need to drive this truck next week 100 miles to a social security doctor. Any ideas what it could be? Do you think he missed something else like messing up the intake or head gasket?

Again it's a 5.4l. And it has 205k on it. Ran fine prior to the exhaust gasket issue. Other weird thing was once this work was done the heater blower went out too. I replaced that as well. Suspect that is a coincidence but still strange.

Oh and I thought I had it solved as the #8 injector was missing it's top fuel rail o ring. But replacing all 8 did not correct the issue.

 

Welcome to the site..

Ran fine before breaking it down..

So, it would seem that coils, injectors, fuel pump 'should' not have been a contributor unless damaged or a coincidence since it ran fine prior. That said, T chains and gaskets,, were replaced and probably more of a potential for cause..

Fuel pressure and volume, you never mentioned values after replacement. If it were chained up wrong it could/would certainly affect bottom end or over all performance. Did you/they install a vacuum gauge and see what it produces at idle?

 

I know it was 20 pounds prior to the new fuel pump. I'm not 100% Sure what it is now. The CEL indicates #8 cylinder misfiring. So that's why #7 and #8 plug and coil were swapped. Problem code stated with #8. That is also the side the head was off.

I only had the plugs and coils changed to basically do a tune up at the same time exhaust manifold gasket was to be changed. Then ran into all the issues with the broken bolts. Figured change the timing set while it was open too, made sense with 205k on it.

I really thought I had it when #8 fuel injector was missing the o ring.

 

Also, before the fuel pump was changed the truck took like 6 times to get it started. The guage showed the pressure drop from 20 lbs when it was finally started and gas was applied. It was also backfiring really bad with the old fuel pump. With the new pump, no backfiring and always starts on the first try. Idles at about 700 rpms pretty much all the time. But when it warms up, it idles rough even though rpms stay pretty constant.

 

It seems possible you have more than one issue..

I'd start with checking for spec fuel pressure.
S/B...
35-45 with Key On, engine Off
28-45 with it running ( pressure should increase with the regulator unplugged and hose blocked off)

Then, Put a vacuum gauge on it and see what it produces at idle. If you should have a compression issue or its chained incorrectly it will show up on the vacuum reading values as low, or a cyl. comp issue may show as an unstable needle reading. Although a valve timing issue would affect more than one cylinder. Just something to rule out if the vacuum if 'off' due to any conditions for cause like gaskets, EGR, PCV, comp, and of course valve timing.

During Open Loop, the cold condition mixture will be commanded richer and a Lean condition (vacuum leak, pressure to a degree) won't be as prominent. Same goes with valve timing, richer can mask a mistake. Backfire can occur in a lean condition (closed loop) and can be a symptom of lower fuel pressure. Low pressure/ volume should show up more as a random or global misfire if a lean condition is present due to low pressure and volume. But again, should show up as a more of a random or multiple cylinders and generally O2 DTC's would be set for no/slow ranging if the lean condition persists. Backfire is through the intake on a throttle snap?

What was the #8 coil DTC?

Compression check going back together never hurts to verify its spec as well. More so if everything else proves and a misfire is present, and can help to prove correct/incorrect valve timing. If you get a hard code on 8, something is wrong. Either a fuel drop issue there (with old and new injectors w/same results, would be suspect, more so with new coils, plugs etc) injector connector, coil connector/coil, compression, spark drops out, vacuum leak. Being it ran fine prior, doubt it would be any kind of coil driver/ distribution issue.

Bring it ran good prior to breaking it down, doesn't make sense that the pump happened to fail within that window of time, or, that an injector/ coil went south unless some sort of damage.

But with new components across the board as it seems, would lead me back to making sure of the basics first. Fuel delivery within specs, compression, spec vacuum ( you found some issue there already) and correct any issues you find before moving forward or adding parts. Verifying COP input and output as well since a coil DTC exists. Even if just installing a plug into a loose mounted coil, grounded plug base, an visually checking a healthy spark during idle...

 

I don't know what the dtc was/is. I thought it was strange the fuel pump went bad too.. but the field guage was broken anyway so figured what the heck. I was going to have that fixed anyway. I do know that the same code was thrown for #8 when the plug and coil were swapped with #7. So I can rule out the coil and plug it think.

I'm gonna have some one pressure test it and get me the code. I have no choice but to drive it 40 miles round trip today. I have no choice but to go to this appt.

I would think that the head gasket leaking or put on wrong would affect all the cylinders. But only 8 is throwing the code. I'm wondering if they didn't tighten down the head right or a bolt is loose in the back of that head. I did find loose valve cover bolts so that has a concern for me.

No other work was done to the head other than drilling out the 4 broken bolts. One was helicoiled (spelling?).

I wondering if it's the wire to the coil myself or the head or vacuum. I did also have the egr changed too. I really like this truck, and need it. I'm thinking it's got to be something that was done wrong or missed.

The head was not machined or anything other than drilling the bolts out. I would think if something had to be done to the head it would affect the entire head or it'd be leaking oil or antifreeze.

It was for sure a lean condition before the new fuel pump, backfiring real bad. Just weird it's just #8 now. With no injector, plug, aND coil...I would expect it to be fine now.

 

I just remembered too...the code on #8 comes and goes. It seems fine then comes back again. It goes back and forth like it clears then comes back. So we thought fuel injector issue. And when I found the missing o ring on top of the injector I thought for sure it was the injector. I dug all around the fuel rail and no o ring.

 

I just realized today that the guy looking at the misfire issues was on the passenger side of the truck not the drivers side when he looed at the issue.

The 5.4L Triton engine has cylinders 1 - 4 on the passenger side and 5 - 8 on the drivers side. So what I was told was #8 was in fact #4 (according to the diagrams I Found online). So I am going to change the plug on the true #8 and move the COP from 8 to 5 and see where the code goes from there (or if changing the plug on the true #8 cyl fixes the issue).

I even went back to the shop to double check with them; they said that #8 is on the passenger side not the drivers side. I said all diagrams show #8 as the last cylinder on the drivers side. He stated I was wrong; so I'm going with all the diagrams out on the internet...and try changing the plug and move the coil pack.

Weird thing is that #4 was not throwing a code but (according to the diagram) that was the one missing the o-ring.

I also picked up a compression tester just in case - I'm thinking that I will most likely return that if the plug fixes the issue or the code moves to #5 instead of #8.

Keep you posted.

 

Update - issue appears to be resolved.

The first mechanic who was to change all the plugs and cop did not change the plugs. Only changed the cop out.

I bought bosch plugs and he wouldn't put them in and asked my neighbor (I was in the hospital) to get champion plugs, which he did. Today we decided to go with the iridium bosch plugs I still had. We pulled out the auto lite platinum plugs I put in 100k miles ago. He never changed the plugs. You could see the plugs were old.

Also found a burnt vacuum hose going to the fuel regulator as well. Appears to be running a lot better now.

 

As I was reading through this I was wondering about the plugs. I am happy to hear that everything seems to be resolved.