Jumping timing
Thread Starter
6th Gear
Joined: Aug 2022
Posts: 6
Likes: 0
From: Norway
Jumping timing
Hi everyone 
I’m new here and I hope it will be a fun adventure
I have a little problem with my C4 89
After I replaced the knock sensor I checked timing and I set it on 6 degrees before TDC.
I took a little ride and looks ok, but when I came back and opened the door I saw that the glass was shaking slightly on Parking.
I checked the ignition with the timing lamp again and found that the marker on the crankshaft wheel jumps and shows from 6 degrees to 8.
It fluctuates all the time between 6 and 8
Sometimes even to 9 degrees.
The engine runs fairly evenly, but it shakes slightly as well as the whole car (it's ok when driving).
I have a new distributor cap, new coil, new distributor control module.
Spark plugs and wires mounted year ago.
What can be a reason of that hesitating timing????
Help guys!!
(sorry for my english which is not perfect. I was learning English by listening to MTV and watching movies
)
I’m new here and I hope it will be a fun adventure
I have a little problem with my C4 89
After I replaced the knock sensor I checked timing and I set it on 6 degrees before TDC.
I took a little ride and looks ok, but when I came back and opened the door I saw that the glass was shaking slightly on Parking.
I checked the ignition with the timing lamp again and found that the marker on the crankshaft wheel jumps and shows from 6 degrees to 8.
It fluctuates all the time between 6 and 8
Sometimes even to 9 degrees.
The engine runs fairly evenly, but it shakes slightly as well as the whole car (it's ok when driving).
I have a new distributor cap, new coil, new distributor control module.
Spark plugs and wires mounted year ago.
What can be a reason of that hesitating timing????
Help guys!! (sorry for my english which is not perfect. I was learning English by listening to MTV and watching movies
)
Thread Starter
6th Gear
Joined: Aug 2022
Posts: 6
Likes: 0
From: Norway
yes, I set the ignition according to the process as it should be. From A to Z. Found instruction here in one post.(disconnect tan/black wire, put trans in Drive…everything as it should be
)It is possible that „pick up coil „ reads feil torque of rotor and thats why ignition is jumpin lil bit?????
Heel & Toe
Joined: May 2022
Posts: 18
Likes: 0
just retimed my 1990 l98 and noticed something very similar, im not too worried about it though. i still have full power and it isnt noticeable unless i pay attention to it. under a timing light it will also jump from about 6-8.
Race Director
Joined: Nov 2003
Posts: 12,220
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
I assume you are "reading" the timing with the EST wire unplugged too. Seems likely since it would jump to the mid 20's (or higher) with it plugged in. It almost sounds like it might be hunting for the correct idle? Vacuum leak? IAC fluctuation? Is the timing the ONLY thing moving? Just because you put a new ignition module in -- doesn't mean it's a "good one". Same with the plug wires....maybe they've touched something and have a bare spot? Is the distributor hold-down tight?
How does it run otherwise?
How does it run otherwise?
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
Wow congratulations on learning English by watching movies! Any way, I think a little jumping of the timing mark can be simply normal wear in the timing components. Timing chain and gears, cam and distributor gears, and the distributor shaft endplay are all involved. The shake you are seeing could be a misfire, but I think you would notice that while driving. Double check the wires are in the right firing order.
