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Extreme Frustration

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Morris

Morris

Yoda
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My car is still running like pooh!

I have thoroughly checked for vacuum leaks. Pulled the throttle body and inspected. Replaced my ignition system. Set my valve clearances... twice! Plugged my EGR system. And I am sure many more things I can't remember right now.

Now I have noticed my timing floating a bit. Roughly 2 degrees in either direction at idle. And my engine vaccum flutters at all speeds all the time. Previously it would have moments of clarity.

What is going on?????
 
Yes they can leak, but my spark advance is now computer controlled, so I no longer have a vacuum advance diaphram.

Could these problems be caused by a loose timing chain?


How bout an exhaust obstruction?
 
What do you use to determine crank position / input for spark control? I know you have a different system, but it sounds like my car before I repaired the mounting plate for the points. The plate would wobble around instead of rotating in a constant plane. As it wobbled it would change the points’ gap and thus the timing. When I went to Pertronix this was lessoned because it is less sensitive to position, but wasn't truly fixed until I got around to replacing the mounting plate. Look for a loose mount somewhere in your system.
 
[ QUOTE ]
My car is still running like pooh!
And my engine vaccum flutters at all speeds all the time. Previously it would have moments of clarity.
What is going on?????

[/ QUOTE ]
I haven't been following your problem closely, forgive me if this has already been covered.
A distinct possibility is that the valves are leaking or sticking. I would run a compression test, or better yet a cylinder leak test to determine if compression is adequate & even on all cylinders. All the tuning in the world wont help if a valve or two are screwed up. The vacuum "flutter" is a pretty good indication. It may be that a sticking valve has finally stuck often enough to permanently burn it.

A couple of degrees of timing variation, while not desirable, certainly won't make an engine run really bad.
D
 
Thanks guys.

Chris, I am triggering from an optical sensor salvaged from my Lumenition system. I had a spare distributor which I "locked out" by drilling a hole in the plate and fitting a screw. I also welded the mechanical advance weights together. I can grab the rotor in turn it roughly 1.5 degree with the dizzy mounted in the car. I assume this is due to slop where the drive dog and dizzy join.

Would a thinner gasket between the block and the dizzy mount fix this?

Dave, I really think it must be a valve problem. My compression reads 140-155#s. But I get a different reading on each cylinder each time I check. My compression tester is a fine Chinese made tool. Regardless, I think you are right and this must be a valve issue. Especially since I have been having sticky valve problems since I had the head rebuilt.

I did not want to believe that valves were the problem because 1) Denial and 2) For a long time the vacuum signal would level out at idle or at cruise. It seemed very unlikely that a burnt/sticking valve would allow that to happen.
 
Do you have a partly sheared cam drive key (or loose cam sprocket bolts)? Maybe the chain too.
 
You have checked the valves, right? New guides right? And a valve still sitcks, right? Or does it just stick a bit? and cause problems running smoothly.

Can you identify the valve in question? If so I am afraid I would pull the head and have a new valve and guide both.

Not the answer you wanted to hear I am sure. But a valve sticking even a bit is big problems. By a bit I mean not closing as fast as it might.
 
Again, I don't know the 1500 at all, but in the A series the distributor drive gear is a worm gear drive off the camshaft. That being said, the cam can turn the dizzy gear, but not vice versa so you should not be picking up timing chain slop (but you still may have it). The dizzy gear will walk up and down the cam gear if it is rotated by hand which may be what you are seeing. This is normal as far as I know - anyone, please chime in if you know otherwise.

What I'm wondering is if your system is too "fast" for the input. What I'm saying is you are driving a computer controller with something that will have a lag to it due to the hysteresis of the mechanical parts (timing chain, dizzy gear, dizzy internals). Most modern systems take the timing input off the crank or camshaft end. Could the computer controller be adjusting too much to the hysteresis and actually compounding the problem? What does a strobe light tell you while accelerating, at constant speed and while decelerating? It should move but not jump back and forth. Also, check it on all four plug wires, you can usually reference something on the pulley (usually oil in my case) and get an idea if there is an intermittent miss fire of something else odd going on. Hopefully we have not gone off topic here, just some thoughts.
 
Just out of curiosity, fire her up &, with it idling, squirt WD-40 all along the head where it meets the block...see if anything changes in the way it idles.
 
Thanks for all the input, guys.

I tried your trick with the WD40, Tony. Nothing changed, but I can't get to the seam beneath the exhaust manifold.
Chris, I will try your suggestions this weekend.

I guess I am down to pulling the head. Though, I have figured out a way to smooth out my vacuum signal so my ECU won't freak out on me.

I have another head. I may just get that one rebuilt (by a machine shop that doesn't SUCK this time) while I keep on driving her.

Nial, are there any symptoms I can look for that will tell me if the problem is somewhere in my timing chain? I reeeeeeeeeally don't want to pull that timing cover.
 
Finally got around to pulling the head.

If you answered sticking valve as the source of my problem, then you win a cupie doll.


What are the odds? 8 new guides and 2 bad ones over the same cylinder. Chewed up the stems real nice.

Now I get to think about all the time and money I spent avoiding pulling the head.

I have got to talk to a shrink about this denial thing.
 
Oh, do you want an address for the cupie doll.

At least it is an easy, cheep fix. Good on ya.

I really hate to say I told ya so but I told ya so.

If it was me I would go with all new guides, valves, and hardened valve seats. Now that's just me you understand. Would also look real close at pushrods and lifters. Just to satisify myself that all was ok you understand.

Think your machine shop owes you some help with this one.
 
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