Jumpy timing????
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 858
Likes: 5
From: Fl,USA
Jumpy timing????
I just noticed while trying to set the base timing on my 89 (est wire disconnected) that the timing jumps back and forth erratically 2 degrees for no apparent reason. Any idea what would cause this? I have long tube headers with dual exhaust. I know the knock sensor does read some false knocks when driving normally but I didn't think the computer could retard timing with the est wire disconnected. Any ideas on this? The timing also seems to jump when the est wire is connected as well.
Thanks for your help!
John
Thanks for your help!
John
Burning Brakes
Joined: Sep 2000
Posts: 1,199
Likes: 1
From: NewCastle IN. USA
Re: Jumpy timing???? (JOHN89)
2 degrees dosn't seem real bad, but if it is doing it alot and making it hard to set the timing, then it could be a problem. (that is if it's idling steady, because if the rpm changes the timing may change even with the est wire disconnected).
here's a few of idea's:
worn distributor drive gear.
worn bushings in distributor housing.
loose / bad rotor or cap
here's a few of idea's:
worn distributor drive gear.
worn bushings in distributor housing.
loose / bad rotor or cap
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
Re: Jumpy timing???? (Greg Johnson)
Greg's got a pretty good guess if you are regularly saying your prayers.
If the rubber has deteriorated in the harmonic balancer the outside ring with the timing mark "could" be moving.....not likely but "could".
If not here's a couple other possibilities.
(Not in any order of probably.)
1)The timing chain/gear may have excessive play/wear. (maybe not)
2)The timing gear on the bottom of the distributor may be worn.
3)A spring (or two) may be off the advance weights in the distributor allowing the weights to move at idle speedsand advance the timing a small amount.
4) The pin in the distributor gear may have somehow worked loose allowing the gear to rock back and forth some. (not likely but possible)
5) Your timing light may be flaking out, try another one.
If it's a high mileage engine and the timing gears/chain hasn't been changed in a long time, I'd highly suspect it.
Can't think of any other things right now.If you want details on how to check any of these things there's lots of folks on here that can explain how to do it including me.
Good luck with it.
If the rubber has deteriorated in the harmonic balancer the outside ring with the timing mark "could" be moving.....not likely but "could".
If not here's a couple other possibilities.
(Not in any order of probably.)
1)The timing chain/gear may have excessive play/wear. (maybe not)
2)The timing gear on the bottom of the distributor may be worn.
3)A spring (or two) may be off the advance weights in the distributor allowing the weights to move at idle speedsand advance the timing a small amount.
4) The pin in the distributor gear may have somehow worked loose allowing the gear to rock back and forth some. (not likely but possible)
5) Your timing light may be flaking out, try another one.
If it's a high mileage engine and the timing gears/chain hasn't been changed in a long time, I'd highly suspect it.
Can't think of any other things right now.If you want details on how to check any of these things there's lots of folks on here that can explain how to do it including me.
Good luck with it.
Instructor
Joined: Mar 2001
Posts: 230
Likes: 1
From: Phila. Pa.
Re: Jumpy timing???? (JOHN89)
Check for exessive play where the distributor fits into the intake manifold. See if it will wobble around alot.I think it's Mr. Gasket that makes a sleeve that fits between the base of the distributor and the manifold that will eliminate this. Summit stocks this part. This problem is most common on aftermarket manifolds but it wouldn't hurt to check it out on a stocker either. If it has been wobbling be sure to check the distributor gear for exessive wear.
