NEED LT5 TIMING FAIL HELP!!!!

[oricale]

Yes i did just buy it,...just trying to get a game plan,...

PETE:,..LOL!,..yes I certainly agree,..I work on 35 million dollar airplanes daily and I am NOT yet qualified to rip ANYTHING apart!,...

I mostly want to get a few ideas to check without tearing the engine apart to make sure I didnt buy a dead vette,..but I am prepared either way,..this is my only chance to own such a great car...($$$)

Also this car just came back from california in 06 and had $4000.00 in exhaust upgrades for the smog requirements,..I cant imagine i need or want all that on for MD or DC..

[tccrab]

My diagnosis is a bad misfire and what you're hearing is the dual mass flywheel rattle.
It can be really scary, especially if the misfire is a bad one.
Misfires typically caused by:
1. Bad Injectors
2. Ignition (plugs, wires, coils)

If I were to be a gambling man, my bet would be on bad primary fuel injectors.

Your car came from the Sacramento CA area, I saw it a couple of years ago on the road not far from my house in Folsom.
Couldn't catch up with him in traffic, never got the chance to talk with the owner.

TomC
'Crabs

[oricale]

**YES**..YOU ARE CORRECT SIR!!!!..I have all the documents from the folsom dealer that did all the work on the smog!!...WOW small world!....

[Pete]

Does the rattle/knock only happen at shut down?

If so that's just the dual mass flywheel no biggie,flywheel just getting old.
If it rattles/knocks at idle and motor shakes,most likely you have a miss.

Before you go any further check MAP sensor back of plenum make sure vacuum hose is connected,easy and free.

Somebody post picture location of MAP.

Pete

[bdw18_123]

I agree with what the rest of the guys here are saying. I just recently finished reassembling/repairing the LT5 in the project '90 ZR-1 I bought over 2 years ago, so I am pretty familiar with the internals of this engine.

Like has already been said, probably not the chains; especially if it looks tight and the compression is good on all the cylinders. They can't 'jump' teeth like a belt can, there would have to be major things broken for that to happen (missing/broken chain guides, etc). Things are too tight in there, they either work, or they break (which was the case with mine, driver's side timing chain was broken when I bought the car).

Yeah, don't try messing with the timing, it is a VERY complicated process and it is not easy, especially if your not familiar with this engine. Not to mention the new parts & special tools you need you need. The whole front end of the engine has to be disassemble to do the timing.

Just get that cam cover back on with anaerobic sealant (Permabond A136 or Loctite 518) and clean the sealing surfaces really good as was suggested. It is VERY important that you follow the torque amounts and sequence in the service manual exactly (see my next post below), due to the cover having the bearing surfaces that the cams ride on built into it.

Also as has already been said, check the MAP sensor hose, coils, plug wires, spark plugs, injectors (if these are still original and your ZR-1 is a 90-92, they are definitely bad or going bad, the original injectors of those years can't handle the ethanol in today's fuel). Can't rule out the ECM as a cause either, as I had that problem; but that is a last resort after checking the usual stuff.


Here are a couple of pics to show where the MAP sensor is and hose that Pete is talking about:

[oricale]

Awesome,..Thank you for the info,...I will do just that,...

I will look into injectors, plugs and wires!,...

I am wondering if there is tell-tale signs of a major issue ?..I am assuming that if its running rough and the timing cannot go out,..then it has to be a spark-fuel-miss- ISSUE?

OR a tell-tale sign that there isint a major issue?

[Kevin]

it's probably an injector or more going bad. i doubt there's any real issue

[bdw18_123]

I would check that MAP sensor hose first, as it is common for it to come off. When it does it makes the engine sound like it has a bad miss or something.

Here are two pages from the LT5 service manual supplement that shows the torque procedure and tightening sequence for the camshaft covers.

[secondchance]

May I ask where the car is at? Call me at 703 980 8814.

[tccrab]

Originally Posted by oricale

<snip>
I am wondering if there is tell-tale signs of a major issue ?
<snip>

Not likely.
The LT5 was "Purpose Engineered and Built".
In plain English, it means that they designed it and built it to be "rode hard and put to bed wet", often.
She's a thoroughbred that was made to run, and built strong enough to take it all and ask for more.
Very few stock LT5's have detonated over the years.
As long as they are properly maintained, they just keep on running.
There are ZR1's out there with well over 100k miles that just keep on keeping on.
You need to read this book, "Heart of the Beast" by Anthony Young:
http://www.amazon.com/Heart-Beast-An.../dp/0971146845
It will give you a real understanding of the Beast that you know own.

Fear not, the Brotherhood of the Beast will help you out.
I absolutely guarantee that a local Brother will be willing to stop in and help out.

For the love of god and everything holy, do not, and I repeat, do not take it to the local Chebby Stealership.
It's highly unlikely that they've ever seen a ZR1, much less diagnose and repair one.
It would be money and time wasted.
Trust me on this.

TomC
'Crabs