Loose Timing chain

[jd0g19]

I have a 91 q45 that was making a knocking noise on the passenger side on the engine. Decided to remove valve cover to investigate. Notice a very loose timing chain. It would only go 45 mph tops. 1): What is the cause of this?2)Where can I find a reapir manual? 3) Can this be repaired or should I replace the engine? Any assistance would be greatly appreciated...

[Jesda]

Was there a severe chain guide failure?

Here's some photos:http://www.q45.org/guidereplacement.html

I apologize for not offering more useful information. Someone else will chime in.

Please stop driving it for now.

-Jesda

[911/Q45]

Was it the large chain at the front of the cams, or the smaller chain in the middle? The one in the middle is normally loose and that doesn't indicate trouble.

[jd0g19]

It's the outter one.

[jd0g19]

My next question is whether or not the knocking noise is the result of the chain jumping off and/or one of the piston are banging around the block?

[DAEDALUS]

Can't rule anything out, but a loose timing chain while stopped doesn't say much about the valvetrain. The crank pulls the chain to the intake cam. The intake cam pulls the chain to the exhaust cam. The slack is taken up by the tensioner. No matter how off the timing might be, the 2 taught legs of the chain will always be taught when the engine is running. After you shut the engine off this can change. The exhaust cam could rotate more than the intake cam, causing slack between the 2. Or both cams could rotate more than the crankshaft, causing slack in the other leg.Of course, if it's *really* loose something's wrong since the tensioner shouldn't allow too much play in it regardless; is it so loose you can change the timing of the chain on the cam by hand?Do a compression check and/or pull off the front cover to see if the chain is aligned right. If it is, then it's something else. Bad bearing? That would be a bad situation. Rebuilding a VH45 would be challenging, but if that's your hobby, you might enjoy it.

[jd0g19]

Thanks for the info. I am currently taking everthing off up front to have a look. I amsupecting that I may have a bent valve or something. Do you any ideas as to where I can get a repair manual. I try some of the auto stores. I still searching. Thanks for the help.

[DAEDALUS]

But have you done enough diagnosis? Have you done the compression check and checked the oil pressure? These things take less time and effort, and in some cases will pinpoint the problem with more certainty than disassembly and observation/measurement. A bent valve, especially, will show up on a compression check.

[jd0g19]

Thanks ...thats what I'll do....

[tonyp71]

Email me if you're interested. It's in Adobe PDF format...and it's GREAT! If anyone else needs a copy, let me know.

-Tony

[jd0g19]

That will Great....!!!!I really appreciate that...

[jd0g19]

I'm not sure how to email you ...but here is my email "[email protected] again....

[pito11213]

Hey if you could also send that service manual to [email protected]

it would be greatly appreciated

[rg541]

I'll take a copy thanks!

e-mail address: [email protected]

[Jesda]

[email protected]

[drftnassmofo]

can anybody here help me w/my 91 fastback's loose chain..i think its loose neways...its like a ticking noise and im sure its the chain b/c the sound is coming from where the chain is..and a mechanic told me itd be about $650 for labor...i CANT pay someone else to do something for my car that i may be able to do..if anybody's got pics or just so happens to have a service manual for a 91 240sx (which i cant find anywhere) that'd be friggin sweet! also..i heard about people advancing the timing a couple degrees...i wouldnt mind pics of that either

[Q45tech]

I assume you have a Nissan [fastback] WRONG Form! DRFTN - *** - MOFO definitely belongs in 240sx land or Nissan Mechanic you might try there, as loose chains are common.

[rg541]

ill take a copy. thanks!!!

[email protected]