strange knocking noise above 2,000 rpm (5.0 efi 95')

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Well, I got it out for a test run. The pump no longer whines and it has more power at lower rpms, but the misfire still exists. I found a few new facts though. When it was just starting up, it got up on a plane and was running pretty good with very little miss. As it warmed up, it missed more often. In fact, after it warmed up, I couldn't get it on a plane because of the miss. I know it isn't with the fuel demand because the engine required more fuel since the air is colder. I know it isn't with the fuel delivery because it is less restrictive when it is warmer. There is no loop in idle to signify a vacuum leak. I'm thinking it may be a sensor that effects fuel/air or timing. I'm about to test the MAP sensor to see if it varies with pressure. Maybe it isn't registering at higher rpms (lower vacuum) and not adjusting the fuel curve making it miss?? Otherwise, maybe the knock sensor is malfunctioning making the timing adjust?? Any hints?

 

[Don S]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Probably your home cleaned injectors plugging back up.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

I really hope that isn't the case. The idle is smoother, the pumps don't whine anymore, and they don't heat up like before.

Someone told me I might have a broken valve spring causing the engine to backfire through the intake and would only effect it under load/higher rpm. Is this a possibility that would be likely?

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

The more I look into it, the more I believe a broken spring, worn cam, or something else mechanical with an intake valve is my problem. It makes sense, it operates fine under light load but backfires back through the intake manifold when pushed. Something is letting that backfire come back into the plenum instead of through the exhaust. I just need time to break it down now.

 

[RogersJetboat454]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

The more I look into it, the more I believe a broken spring, worn cam, or something else mechanical with an intake valve is my problem. It makes sense, it operates fine under light load but backfires back through the intake manifold when pushed. Something is letting that backfire come back into the plenum instead of through the exhaust. I just need time to break it down now.

Just out of curiosity, did you ever check compression? Cover the very basics first before you start ripping the engine apart, and make it so you can't turn the engine over. If your compression results show issues, it would give you the right hole(s) to focus on rather than playing the guessing game with all 8. If a compression test looks relatively normal, pull your valve covers first and have a look.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

I never did a compression test when I got it because I believed the guy that sold me it. I figured it was a small problem that arose from sitting out of water for a few seasons. I never believed it was a scam (if it is). I just found out a family member has less that a week of life left so it'll be a little bit before I return to the boat. I'm going to keep updating this until I figure it out.

My next test was going to run it with each plug wire off "one at a time" and see if my miss is caused my one particular cylinder or all cylinders to narrow it down. If you know the 5.0's, it is practically impossible to remove the plugs without taking off the exhaust manifolds. So it is not the easiest task to do a comp. test on each cylinder.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

And so the problem is drastically narrowed down! I took the boat out and found that all my backfire is coming from one cylinder. I took off the plug wires one at a time to test it. When I took the one plug wire off for a minute it went away completely. All my problems are from one cylinder. I also found that it isn't the temp that affects the backfire. It is the oil pressure. When I start out and the oil pressure is high (gauge maxed), it hardly backfires at all. When it warms up the the oil pressure regulates (around 60psi), it backfires more consistantly. Since the oil was so bad in the engine when I got the boat (had to change it completely 2 times to get a decently clean color), I'm thinking maybe I'll get lucky and it will only be a sticking lifter. What do you guys think?

 

[Bondo]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

I never did a compression test when I got it because I believed the guy that sold me it. I figured it was a small problem that arose from sitting out of water for a few seasons. I never believed it was a scam (if it is). I just found out a family member has less that a week of life left so it'll be a little bit before I return to the boat. I'm going to keep updating this until I figure it out.

My next test was going to run it with each plug wire off "one at a time" and see if my miss is caused my one particular cylinder or all cylinders to narrow it down. If you know the 5.0's, it is practically impossible to remove the plugs without taking off the exhaust manifolds. So it is not the easiest task to do a comp. test on each cylinder.

Ayuh,.... No Wonder yer up to nearly 70 posts, Without an Answer.....
Are ya tryin' to Fix this thing,..?? or write a Book,..??

You've completely Skipped the most basic of diagnostic Tests....

'n there's instructions all over the internet, 'bout grindin' down a socket wrench to get to those darn Ford sparkplugs...

A compression tester with the rubber hose, screws in Easily....
'course, slippin' a piece of soft rubber fuel line onto the spark plug, makes them screw in easier too...

I'm thinking maybe I'll get lucky and it will only be a sticking lifter. What do you guys think?

Ayuh,.... I think yer Dreamin',.... til ya Test yer theory...

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

bond-o: Yeah, I should have done the compression test. It seemed like such a minor fix in the beginning, I almost rulled out the fact it could be something mechanical internally. I did find about 10 other things along the way that needed addressed with worn out parts. I regret not finding the problems earlier, but I'm glad I found out all the other wrong things that would have left me stranded.

Well, I got the valve cover off. No broken springs. No uneven play in the components. I took out the rods and lifters. Nothing looks worn or dished. I looked down through the lifter slot and checked out the cam. It doesn't look worn either. I removed the head and no damages to the walls or piston top. It was completely covered in black carbon. In that cylinder, my one new plug I just put in with less than 5 hours on it is completely blackened. It was black in the intake port as well so it has to be something with the valves/lifters. I planned on taking it to a machine shop to clean/check them out. I don't have the tools to go any further myself. Any thing you can suggest?

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Well, the machine shop said that the actual parts of the head (valves, springs, rocker arms, ec...) and still in tolerance but the head does need a valve job. The one cylinder was not closing all the way which he believes was a pumped up, stuck lifter. I'm getting new lifters and having a valve job done. He said $300 and he'd do both so I can't argue. So close to the end......

 

[Jammer864]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Make sure you let us know. I hoping there is no sequel to this novel though. Good luck.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Yeah, I'll definately keep everyone updated. I read as many trouble threads as I could when I first had this problem so hopefully my pages will help someone in the future. My biggest issues were not doing the basic tests, assuming, and believing the seller.

The heads are in the shop now. I might get it back by the end of this week or beginning of next week. I got everything ordered and ready to reinstall except for the exhaust manifold bolts. Some are looking rough and worn so I'll be replacing them. I just got to locate some (hopefully under the $11 each price tag I've found so far).

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Damn! I still have the misfire even with the new heads/seals. It is still in cylinder 4. I pulled off the spark plug wire, spark plug, and injector and changed them to different cylinders. The miss still stays in cylinder 4. That means it is wiring or what?

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

I forgot to mention, I did a compression test on cylinder 1, 4, and 8 (the easy ones to get to except my trouble cylinder 4). All reading came out between 115-120. I had to grind down the shaft on my compression tester because it was one with both size threads and the larger threads wouldn't let it thread into the recessed holes on the boat. Those readings were without being able to use the o-ring that came with it so I'm sure the actual readings are higher. . . yet consistant with each other.

 

[bruceb58]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Did you not do a compression test before you put the exhaust manifolds back on?

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

No, I didn't do the test with the manfolds off. I thought my problem was fixed. I would have had to grind the tester down anyways because of how mine was designed. Even though it made it harder for me to test, it still gave me reading within 5% of my trouble cylinder and the other properly working ones.

I was thinking it might have to do with the pip sensor in the distributor. If the wheel is damaged, worn, or corroded on the section that tells cylinder 4 to fire, it might be giving me my misfire under higher load/speed. It would also explain the higher trouble at hotter temperatures. What do you think?

Also, the injection system is bank injection? If so, that means that it can't be a loss of injection signal or it would effect other cylinders? I'm almost there!

 

[bruceb58]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Your readings of 115-120 are low to me. If it were my boat, I would be investigating these low readings.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

I took those reading with a very old, dusty gauge along with a grinded-down tip seal without an o-ring. I'll get a new tester (or rent one from autozone) to get a more accurate reading.

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

Well, just tested my ignition module and it read "fail" at autozone. I bought a new one with a new distributor w/ PIP since they usually work together and I still have my miss. The boat runs quite a bit better but still has the random miss in cylinder 4. I don't get it, the boat can get up on a plane, run to WOT, and is very smooth idle but has the strange miss. What else can it be?

Does the EFI 5.0 have bank injection and does the cylinder fire once or twice per cycle?

 

[perna00]

Re: strange knocking noise above 2,000 rpm (5.0 efi 95')

When I get my miss, the plugs are carbon files. . . if it helps.