altima 93 unstable ignition timing


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altima 93 unstable ignition timing

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ioanmachiman
Novice

Feb 9, 2006, 9:20 PM

Post #1 of 4 (4733 views)

altima 93 unstable ignition timing	Sign In

hi

I started to have troubles with poor gas mileage. I checked the ignition timing using a timing light, and
a haynes repair manual. The mark (20 btdc) on the crankshaft pulley is aligned with the timing pointer but:
for a while with a random duration they are aligned, then for another while with a random duration the mark disappears; then again appears and they are aligned, then disappears again, all of them with random durations.
These random durations suggest something wrong but i don't know what can it be
The rmp looks to be constant around 700.

any help appreciated

ty

DanD
Veteran / Moderator
DanD profile image

Feb 10, 2006, 4:53 AM

Post #2 of 4 (4724 views)

Re: altima 93 unstable ignition timing	Sign In

Did you disconnect the TPS while you did the check? They want that done to take timing control away from the computer.
I’ve had this happen that the inductive pick-up of the timing light will be picking up interference from another ignition wire; try moving the pick-up to a different location along the wire.
Also if the ignition wires have very high resistance maybe the pick-up is just loosing its signal. Rule of thumb 10.000 ohms per foot of ignition wire maximum.
I don’t know what brand of timing light you have but if it’s a walmart special that’s the problem right there.
I don’t think it’s the actual timing changing that much; if it were changing to the point of not seeing the mark you would hear and see a change in the engines running.
Dan.

Canadian "EH"

Guest
Anonymous Poster

Feb 10, 2006, 8:05 AM

Post #3 of 4 (4722 views)

Re: altima 93 unstable ignition timing	Sign In

Ty for your reply Dan.
I disconnected the tps sensor. Interference with another wire cant be while I took the signal from the first cylinder near the spark plug (maybe losing the signal through the ground?). The timing light flashes so it has signal but at the wrong moment. I will go and check the timing light.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 10, 2006, 9:01 AM

Post #4 of 4 (4721 views)

Re: altima 93 unstable ignition timing	Sign In

I have a wicked cool Snap-On Advance timing light now about 30 years old but awesome tool. I like to work outdoors when I can so I just put a dot of white auto touch up paint on the marks which helps. Also cleaning the wire and with a Q-tip the contacts of the pick up with like rubbing alcholol has helped me. I suppose carb cleaner or brake cleaner would work but I chosen for milder stuff.

Also: If you have a rubber timing belt and can't tell how old it is trash it NOW! If your timing is jumping around with it jumping around you are in trouble.!! T

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