need some help diagnosing a rough idle after rebuild

[smaring]

Hey guys,

I'm new to the forums here. I have a 2001 4.6L that I recently finished "refreshing" after a loud bang and smoke pouring out the exhaust like crazy. I figured I was lucky to make it in the driveway.

It had a broken timing chain guide and a valve that was a bit bent. I presume the later happened when the chain jumped what appeared to be a few sprocket teeth and got out of timing. That would certainly explain how terrible it was running before barely getting it home.

I gave it new head gaskets and bolts, a replacement valve, new valve seals, new valve springs, a few new rocker arms, new plenum gasket, new valve cover gaskets, new timing cover gasket, new timing chain guides and tensioners, new oil pump, new water pump, new oil adapter gasket, oil pressure sensor, new head temperature sensor, new thermostat, new egr valve and tube, new exhaust manifolds, new oil pan gasket, new transmission fluid filter, new air and oil filters, new spark plugs, a few new hoses, and a new idle air controller.

I WISH while I had the engine lifted a bit to get the oil pan out I would have replaced the engine mounts. It was a poor choice not to.

I cleaned up the top of the pistons, the heads, and lapped the valves. They were in pretty rough shape. I sprayed carb cleaner through the fuel injectors to ensure they were clean. I ensured the timing was proper for a Romeo.

After starting the engine it would still blow some white smoke for about 10 seconds and the idle after putting it in gear was pretty rough. My basic ODB scanner said the system was running lean.

I made a smoke machine and ensured there were no vacuum leaks. I did not test in the direction of the EVAP system. I then guessed at some possible reasons for the poor idle and smoke and I put in a new fuel pressure regulator, new fuel injectors, and a new mass airflow sensor. That seems to have helped the white smoke, but the idle is still a bit rough.

I got tired of throwing money at the wrong problem and picked up a Veepeak bluetooth ODB scanner.

The "FREEZE FRAME - FIRST OCCURRENCE" below was likely before I changed the fuel injectors, fuel regulator, and mass airflow sensor. The other two screens were taken at idle this morning. It is still idling pretty rough (too lean) and doesn't have much power to accelerate. I'll admit I'm a noob when it comes to understanding the significance of the O2 and fuel trim values.

Any opinions with regard to what this is telling me would be greatly appreciated. I would guess O2 sensors but my wallet is getting pretty tired of the guess-work that doesn't pan out.

Thanks,
Steve
Titusville, FL

 

[Hamfisted]

So you know you bent a valve(s), and you didn't have the heads rebuilt at a machine shop ? How many miles on the motor ?
The rear oxygen sensor on the driver's side is dead too. Is it plugged in ? You can swap 'em from side to side and see if the zero voltage follows the oxygen sensor. Then replace it with a new one if it does. Or you can just replace it with a new one rather than move it to the other side. Whatever you feel like doing. Any new DTC codes ?






.

 

[smaring]

280K miles on it. The degree to which the valve was bent only created a bit of resistance in the valve guide. I noticed it while lapping the valves. I saw no impact marks on the top of the piston so I don't know if maybe it hadn't always been that way. I put a straight-edge all over the block and head surfaces, but the feeler gauges said it was within tolerance.

It looks like I can get all (4) for $41 on Amazon. https://a.co/d/9s0LJG3 I may give that a try.

Nothing else too shocking on the codes. I'm aware that my "check engine" light does not work.

 

[smaring]

You would think running lean would cause you to have good gas mileage. I just logged a trip with ODB Fusion and this Veepeak and I'm getting 12.6 MPG. I read somebody suggesting that if its so lean that you aren't getting combustion that that can happen. I guess that's because you then have to run at a higher RPM than you normally would to go the same distance. Its a bit hard for me to wrap my head around.

 

[Vincent Vega]

Steve, In addition to what Hamfisted said, check the MAF sensor and make sure it is clean. You said you replaced the MAF - if the old one was not bad and you kept it, try installing it and see if it helps. Did you replace the intake manifold, and if so did you tighten it per the Ford torquing sequence? The 5.4L uses a plastic manifold that warps over time and causes lean codes and/or coolant leaks, not sure if your 4.6 uses the same manifold.
I know you did a smoke test but Make sure the PCV tubing is ok. Very very common cause of lean codes for both banks on these. Did you do a visual check on all the vacuum hosing? Does it all fit tight? Autozone and cheap hosing may not (I found this out the hard way). Were you able to hit the new EGR with the smoke test?
Did you replace the injector o-rings? Did the fuel rail get a tight fit on the injectors?
Did you use Motorcraft parts, or cheap Amazon stuff. I have been burned several times by new cheap parts that were bad right out of the box. And it sounds like you replaced several parts that have vac connections.
These are basic/obvious ideas, but on the 5.4/4.6 are the most common reasons for 2 banks lean. And revisiting basics helps after being frustrated by this stuff for days or weeks. Good luck.

 

[rothstar]

Steve, I just finished almost the same saga with my 1999 5.4L; I refreshed and replaced almost all the same things you did. When I fired it up (it took me one year to complete), I expected a brand new engine, but there were some hiccups. Here are some thoughts for you based on my very recent experience:
1) White smoke-- When I lifted my heads, some coolant poured down into the crankcase, and I didn't find it until I was about to fill up the oil to start the vehicle. I had to waste one oil change in one day to get the coolant rinsed out of the crankcase. Check your oil to make sure it's not milky or brown--it should be clear. You may need to loosen your drain plug and let some oil drain into a glass jar to look at it.
2) Rough idle-- Mine stumbled, hesitated, and misfired like crazy. Finally I got a misfire code on #3; I moved the #3 coil to #2 and the misfire code followed. I had replaced all the spark plugs but reused the original Motorcraft coils. Replacing the bad coil fixed my misfires. You didn't mention coils and plugs; did you replace the coils and plugs with Motorcraft parts?
3) Lean condition-- Before finding the bad coil I replaced my fuel filter; it was full of cinder like black stuff. That didn't fix my misfire, but I was glad I put a clean one in.
4) Scan data-- Your Sensor 1 O2s should be constantly switching between roughly 0.1 and 0.8. Your Sensor 2 O2s should be staying fairly constant somewhere around 0.5. You deffinately have an O2 problem, but whether the O2s are doing their job and detecting a lean/rich problem, or the O2s are bad is beyond my skill level to know.
4) Big bang-- You did not mention what the initial big bang was. Are you sure you didn't blow a spark plug?

 

[studabaker]

I can say a few things with certainty. If your vehicle is in one gear and you are going a specific speed the rpm will be constant. Transmission issues aside, you will not rev at higher rpm due to lean condition at a specific speed. If you were revving at a higher rpm, at a specific speed, than before you would have catastrophic drive line issue. Lean is your stoichiometry is off, this is the air fuel ratio. What would happen is you would have power loss at lower rpm and a slow acceleration but once you gained rpm it might smooth out a bit.


You seem knowledgeable on a lot of these issues. I think you could benefit from a more scientific approach. Systematically identify the work that you have done and what would be the most likely thing to double check?

Exhaust manifold for example is an interesting swap. I have had the bolts break and I have had a bad seal from my exhaust manifold to the block. Put a wrench on those exhaust manifold bolts. If one of those is loose then torque it to spec. Also consider that those get really hot and what may have been torqued previously, may not be anymore.

I did not see coil packs on your list. Technically a coil over plug would cause a rich condition because it would misfire (not spark - but it may still inject fuel). I have had issues with this because they do not always throw a code. They are fifty bucks, so get one and move it around to look for change, if you suspect that. Again look for a failure before spending money. I have also learned this lesson. The spark plug failure is a common issue as well and makes a loud noise. I have had one blow out. I did not have smoke. i shut my engine off right away, which is something I would advise someone to do if their engine starts making very loud noises.

There are two ways to repair a blown out plug and one of them is from the top. It involves drilling out the threads and installing a new thread (helicoil). The other way is "time-sert" which involves the head being removed, they drill it the threads again but it is installed from inside. The helicoil could get you to the point where you are ready to do the "time-sert". I bring this up because of the loud noise you heard.

Lean code suggests a fuel issue such as the pump. It is not as bad as it seems to do this job. I just did not want to work on the fuel system. I hired a guy once who hit the tank with a wrench and broke my plastic thing over the throttle body and it actually started. Fuel pumps are finicky. I can do better than that guy. It takes a few hours to replace the fuel pump.

you are right to look at vacuum because the egr and at least uses vacuum, i think iac uses vacuum also. I think you know that because you were doing the smoke test. you can use a gauge to measure the vacuum by disconnecting a hose and blocking it off...

I understand it appears to be a timing chain problem and I am not a mechanic. I am still trying to perfect my own engine. I hope I helped rather than made is worse. I didnt mean to suggest a transmission issue, just that the rpm and speed are a constant ratio... If you have higher rpm there would be slippage which would reduce mileage and increase with speed and you would not be able to go above a certain speed, probably.

 

[studabaker]

I also wanted to say o2 sensors a different up by the block (it should go up and down) and be steady back by the muffler, on a graph. So a screen shot of values does not tell you anything, anything g is wrong anyway. It's says they're working. You can tell more from the o2 sensors such as rich or lean. Bank one or two/ left or right.