| Author |
Message |
JM
Guest
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 Posted:
Thu Dec 02, 2004 4:56 am Post subject:
Idle and Timing question |
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Hi folks,
I've asked before I think about the idle in my 99 Altima. It seems to
consitently idle between 800 and 900 rpm, usually around 820 or so according
to the timing light/tach I bought. I checked the timing at idle today and
it seemed to be quite retarded from where it's supposed to be. According to
my service manual it should be at 20 deg. BTDC at idle, which is the mark
closest to the front of the engine on the flywheel, but when I checked it,
it was at least 2 marks (10 deg.) back.
So, I advanced the timing by turning the distributor, and this made the idle
run up to about 930 rpm. But, it seemed to fix a slight slugishness I've
been noticing, and a slight stumble at a few rpm ranges below 2500 rpm.
I'm guessing that the previous owner had it to some "mechanic" that
compensated for the idle by cranking the timing back instead of fixing it
properly. Would you guys agree? I'm going to try and get hold of the
dealer service manager tomorrow and run that by him. My only point of
confusion is the fact that the timing affects the idle at all.. In my '94 I
adjusted the timing ahead after it had been set back (due to a bad knock
sensor which I had replaced) and I didn't notice any change in idle. I
haven't had a chance to go out and test both extremes with it just yet
though, so I could be wrong on that point.
Any thoughts?
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Woody
Guest
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| Posted:
Thu Dec 02, 2004 7:11 pm Post subject:
Re: Idle and Timing question |
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You are adjusting the timing while it is under control of the computer.
There are special procedures to disable it and set base timing. Get a
service manual and follow the correct procedure....
"JM" <jmsn@ns.ns.sympatico.ca> wrote in message
news:aTsrd.188989$Np3.7696497@ursa-nb00s0.nbnet.nb.ca...
| Quote: | Hi folks,
I've asked before I think about the idle in my 99 Altima. It seems to
consitently idle between 800 and 900 rpm, usually around 820 or so
according
to the timing light/tach I bought. I checked the timing at idle today and
it seemed to be quite retarded from where it's supposed to be. According
to
my service manual it should be at 20 deg. BTDC at idle, which is the mark
closest to the front of the engine on the flywheel, but when I checked it,
it was at least 2 marks (10 deg.) back.
So, I advanced the timing by turning the distributor, and this made the
idle
run up to about 930 rpm. But, it seemed to fix a slight slugishness I've
been noticing, and a slight stumble at a few rpm ranges below 2500 rpm.
I'm guessing that the previous owner had it to some "mechanic" that
compensated for the idle by cranking the timing back instead of fixing it
properly. Would you guys agree? I'm going to try and get hold of the
dealer service manager tomorrow and run that by him. My only point of
confusion is the fact that the timing affects the idle at all.. In my '94
I
adjusted the timing ahead after it had been set back (due to a bad knock
sensor which I had replaced) and I didn't notice any change in idle. I
haven't had a chance to go out and test both extremes with it just yet
though, so I could be wrong on that point.
Any thoughts?
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Steve
Guest
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| Posted:
Thu Dec 02, 2004 8:43 pm Post subject:
Re: Idle and Timing question |
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JM wrote:
| Quote: | Hi folks,
I've asked before I think about the idle in my 99 Altima. It seems to
consitently idle between 800 and 900 rpm, usually around 820 or so according
to the timing light/tach I bought. I checked the timing at idle today and
it seemed to be quite retarded from where it's supposed to be. According to
my service manual it should be at 20 deg. BTDC at idle, which is the mark
closest to the front of the engine on the flywheel, but when I checked it,
it was at least 2 marks (10 deg.) back.
So, I advanced the timing by turning the distributor, and this made the idle
run up to about 930 rpm. But, it seemed to fix a slight slugishness I've
been noticing, and a slight stumble at a few rpm ranges below 2500 rpm.
I'm guessing that the previous owner had it to some "mechanic" that
compensated for the idle by cranking the timing back instead of fixing it
properly. Would you guys agree? I'm going to try and get hold of the
dealer service manager tomorrow and run that by him. My only point of
confusion is the fact that the timing affects the idle at all.. In my '94 I
adjusted the timing ahead after it had been set back (due to a bad knock
sensor which I had replaced) and I didn't notice any change in idle. I
haven't had a chance to go out and test both extremes with it just yet
though, so I could be wrong on that point.
Any thoughts?
|
When you checked the timing at idle, did you follow the factory
recommended procecure? MOST vehicles that still had adjustable timing
and computer controlled ignition (its really a '99? I can't believe
anything that late still had distributor-adjustable timing!) require
that you either disconnect a sensor, jumper a wire, or do SOMETHING to
override the computer and just check the basic mechanical timing.
Otherwise, you get into a shoving match with the computer and who knows
WHAT you do to the actual timing curve.
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SteveB
Guest
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| Posted:
Fri Dec 03, 2004 12:30 am Post subject:
Re: Idle and Timing question |
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"Steve" <no@spam.thanks> wrote in message
news:KPudnVwrjpSCpTLcRVn-1Q@texas.net...
its really a '99? I can't believe anything that late still had
distributor-adjustable timing!
Nissans never had any problems with their distributor endowed ECU systems.
Just because something new comes along it doesn't necessarily mean it's
better, it could just be cheaper to make, hence more profit.
I used to have a '50s motorbike 20 yrs ago with magneto ignition and the
spark on that was phenomenal compared with the later battery/coil ignition
systems of the pre-electronic era. They dropped magnetos because they were
very expensive to manufacture, not because of poor performance. |
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Steve
Guest
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| Posted:
Fri Dec 03, 2004 1:27 am Post subject:
Re: Idle and Timing question |
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SteveB wrote:
| Quote: | "Steve" <no@spam.thanks> wrote in message
news:KPudnVwrjpSCpTLcRVn-1Q@texas.net...
its really a '99? I can't believe anything that late still had
distributor-adjustable timing!
Nissans never had any problems with their distributor endowed ECU systems.
|
Its not the question of having a distributor- lots of EFI/ECU systems
have distributors, but its been > 10 years since *most* of them used the
distributor to set or adjust the base timing. That's generally done with
a crank position sensor (fixed timing reference) and then the advance
curve is adjusted entirely in software. The distributor then does
nothing except direct the spark to the correct cylinder, and rotating it
in the block does nothing to the timing (but can screw up the phasing of
the cap to the rotor, but thats another issue...). The last car I had
that used the distributor to control the ECU's view of timing was an 84
Cadillac.
| Quote: | Just because something new comes along it doesn't necessarily mean it's
better, it could just be cheaper to make, hence more profit.
|
Or the old way of doing it could even be better. Far be it from me to
EVER claim that "newer is always better." |
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JM
Guest
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| Posted:
Fri Dec 03, 2004 2:55 am Post subject:
Re: Idle and Timing question |
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Well I do have the factory service manual, but I missed the part where you
have to unplug the TPS before checking the timing the first time around.. I
guess that's one of the perils of doing this kind of stuff at night in the
dark (gotta love winter!). I did it properly tonight and it looks like the
timing was set pretty much in the right place anyway, but the idle is still
a problem.
I did notice that after disabling the TPS, changing the angle of the
distributor still affected the idle speed.. is there any way around this in
this car, or is the proper procedure, if one wanted to advance the base
timing a little bit, to set timing "to taste" and then set the idle speed to
factory spec?
"Woody" <TheDuck@pond.net> wrote in message
news:7oFrd.1437$nE7.617@newssvr17.news.prodigy.com...
| Quote: | You are adjusting the timing while it is under control of the computer.
There are special procedures to disable it and set base timing. Get a
service manual and follow the correct procedure.... |
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