Valvetrain rattle-no power

[firedane]

Well, I guess I need to thing about the infamous chain problem. Fuel rail pressures are good, Ignition seems good, and no vacuum leaks from plenum job. When I rev engine above 1500rpm it sounds like an engine with no oil in lifters. I changed oil and checked for garbage-looks clean. Noise seems to be from pass. side bank. Other thought is collapsed lifters. I am going to check compression tonite and go from there. I know chain job can be accomplished in-frame, but can I pull the heads in-frame? I may need to inspect the valves. How much of a timing problem can these engines survive without fatal problems between the valves and pistons? Oh- fuel rail pressure 35 at idle and 44 without the vaccum connected

firedane

[Q45tech]

Each tooth on the cam gear is 10 degrees, on the crank gear it's 20 degrees. One cam tooth is no problem, 2 is iffy, 3 is 95% sure.

You can take the heads off with the engine in the bay but all in all dropping the engine doesn't add more than 4-5 hours and much easier on your back cause if you have bent valves good idea to change the rods for that cylinder and bearings as they may be bent/worn also. At the very least you should check them for straightness.

[firedane]

Q45tech- you are probably correct. If I have bent valves, I know that the bottom end may have sustained damage. I am hoping that it is a on tooth or one guide deal. The car starts and runs. I have not brought it above 3000 for more than a few seconds and it will reach 50mph, possibly more but I did not try. Accelleration is not bad, it did the above as easily as my 350cid pickup. Cold idle is also smooth yet. Noise starts at about 2000rpm. Related to advance on cams maybe? When I had the covers off the top sprockets looked good. Cam lobes were clean, and no sludge in upper end. Nice brown stain on aluminum and that was it. Stoopid questions- collapsed lifters? multiple bad injectors(never had bad injectors make this loud a rattle) And thanks for the technical info, I know people sometimes say you go a little deep on the answers, but I find the engineering data to be interesting and helpful. The info on fuel regulator was great. I actually put a vacuum source on and pulled it down and checked the inlet rail pressure vs. internal rail pressure.

firedane

[landtodd]

I think this is a really good time to suggest not running the motor, definitely not driving it.

If it's jumped one tooth already . . . you're playing with fire. When the engine grenades, it's not economical to repair. Replacement is about the only cost-effective option.

Your signature suggests you want to keep the car. Well, you need to do the guides anyway, so pop that cover off and confirm or deny that suspicion at least.

[firedane]

Once I confirmed the noise was mechanical I backed it in the garage and got ready to strip it down. Called Scottsdale and asked them to e-mail me a current price on the chains and guides etc. I will compare them to my prices at work and go from there. (Sometimes it can help to work at an auto parts store when you own a Q45!! ) The road back to new is strewn with broken parts but I'm sure the end is worth it. I have a new fuel pump on the back seat and am contemplating the best way to afford repair on the active suspension. However, The motor is first. I am trying to borrow a digital camera to record the effort in detail. If not I will go conventional and get the people at Kodak to do the honors for me. I look at this in a positive light. I have always wanted t see how the engine was constructed to understand it better. Now I have the chance

firedane

[maxnix]

Good attitude!

May the Shop Manual be with you. (It's not with me, yet.)

There are some photos around from Daedalus and I think LonAllen, but they haven't posted yet. A digital camera will save you a lot of frustration, film development costs and film processing time lag if you can get one. It doesn't have to be a killer 5MB one either.

[firedane]

Well, It looks like conventional camera, Kodak and my trusty scanner. Plus side- I have a VHS-C, a tripod, and a friend willing to convert to digital. Maybe you guys will be able to here me smacking my knuckles and sacrificing saki to the east. Yes, I have both the big and the small manuals for the Q. Everyone cross your fingers that the valves aren't bent. Otherwise I guess you'll see pictures of how to drop a drivetrain using a backhoe, big jackstands, and a fiew friends:ylsuper

firedane

[AZhitman]

Firedane - You're my HERO! A lesser Q owner would have given up by now. Here's wishing you Godspeed and no busted knuckles in your endeavour.

Looking forward to the video!

[Q451990]

Sounds like you may be in OK shape... did you hear any backfiring through the exhaust?? When my guides went it felt like I lost about 70% of my engine power and heard a lot of backfire, pinging, etc. One slightly bent valve. You may be fortunate enough to have only slipped a tooth. I think one tooth and you're OK, two and you have engine damage.

I was really lucky to get out with $2800. They replaced guides, chains, sprockets, valves, seals, etc, on one cylinder, and put it back together. It's been fine for 60K!

Heath

[firedane]

Heath - loss of power, slappy rattle reminding one of the sound a set of lifters make when out of oil. No backfire!! A bit hard to start and erattic idle. Will stall after warming up as soon as it is put into gear. The rattle started out at 2000 and up. I believe it comes in at that speed due to chain slack and tension against the guide. Hydraulic advance system may also come into play. I also noticed my fuel rail bleeding off pressure from 37psi to 10 in about 3-5 hours. This may be why I see a bit of blue smoke from the exhaust. That and the extended crank (7-10 sec.) AZ- don't label me a hero. I just refuse to quit. Remember, it is all a matter of perspective. An ace Infiniti mechanic is still a person. They just have the advantage of a consult, a better garage, and specialized training. We are fortunate that they choose to share the last item with us. Ask any one of them how they got good at what they do. Training-training-training. And familiarity with the product.

firedaneMedina, Ohio

[firedane]

Just looked at my post. Guess being tired has a disadvantage. I see a few errors here and there. Oh well, you all get the idea.

firedane

[Q451990]

Heath - loss of power, slappy rattle reminding one of the sound a set of lifters make when out of oil.

Does your low oil pressure light come on? Your oil pump chain my be damaged as well. In any case I'd say that starting the car is a bad idea... if your engine is still running and the guides have self destructed, then you're the only other case I've heard of other than mine! Usually they just stop.

Heath

[landtodd]

I am trying to borrow a digital camera to record the effort in detail. If not I will go conventional and get the people at Kodak to do the honors for me. I look at this in a positive light. I have always wanted t see how the engine was constructed to understand it better. Now I have the chance

firedane

The Kodak disposible is a great solution -- I'm usually too greasy to want to touch an expensive digital, and geting clean enough takes too much time/effort. I speak from experience -- when I did my chain guides, I got my digital camera out, and didn't touch it again until the job was done.

I know what you mean about the positive light. I have much less fear & trepidation, much more "intimate" understanding of that great motor now. Best of luck! May the Dennis be with you!

[landtodd]

if your engine is still running and the guides have self destructed, then you're the only other case I've heard of other than mine! Usually they just stop.

Heath

Remember the guy from Pensacola who said he did his chain guides in a couple of hours, back on the old group (maybe even back in Yahoo days)? His guides had completely deserted him, but he never jumped time, either, so there's another example for you.

This guy was the one with a girlfriend whose son "borrowed" the Q, then did burnouts until a piston exited the motor. I saw the damage for myself. Nice guy, but I don't think he ever got another Q. Last I heard, he was going to do something wild like put a 427 he had on hand in the Q-carcass. He made me laugh. In a good way.

[DAEDALUS]

My driver-side guide was in the oil pan when it was replaced at 213K. The way I see it, a chain will jump time only if derailed by a foreign object, or when given the right combination of crankshaft deceleration and vertical acceleration (it is nominally under tension, after all). For example, letting completely off the gas from 6000RPM in 3rd gear while hitting a bump might cause a derailement. Given good roads and smooth operating conditions, I don't see any reason for the chain to jump even without a tension guide in place.Todd, you don't wear gloves when you work on the car? I get 200 latex gloves for $8 from Costco. Just tear them off to take a few pics, then put them back on. It is so convenient being able to see the pic when you snap it and to not have to wait for development.

[landtodd]

A while back, I believe Dennis said that it's usually the driver's side that goes. Yup, the theory is that the plastic pieces wedge between chain and sprocket where they cause broken chain or just skipped teeth.

So, a big piece lets go, and it's like a pinball game whether it lodges or falls through "safely." Of course, even if it falls through, you still have to worry about larger pieces in the pan clogging the oil pickup, or smaller pieces getting sucked up and scoring the oil pump vanes. Either scenerio can result in dangerously low oil pressure.

My suspicion, and that's all it really is without forensic investigation, is that this is what happened to the friend mentioned above -- oil starvation. His guides were gnawed down to nothing, and to my knowledge, he never accounted for all the pieces.