Ignition timing- what's normal?

Ignition timing- what's normal?

Postby Clevis [OP] » April 10th 2014, 5:32pm

Hi all, I know I can't adjust the timing on my 99. But what does normal advance look like. I may be having some pining and I want to rule out timing. Reading my cheap-o OBD2 it looks like my highest advance is around 38 deg and idle can be around 18.
Are these high? The numbers read from my OBD2 I can assume to mean before TDC, correct?
One last question- how is the advance controlled on these vans? Somewhere in the distributor based on electrical signal? Thanks
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Re: Ignition timing- what's normal?

Postby chevymaher » April 10th 2014, 6:19pm

Idle is about right. and the 38 is a couple degrees to much. But in the realm of normal. 34-36 total 12-16 initial.
It is in the ballpark but a tad high.
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Re: Ignition timing- what's normal?

Postby Corsemoto » April 10th 2014, 6:37pm

FSM description:

Enhanced Ignition System Description

The ignition system initiates combustion by providing a spark to ignite the compressed air and fuel mixture at the correct time. In order to provide an improved engine performance, fuel economy, and control of exhaust emissions, the control module controls the distributor spark advance, or timing, with the ignition control (IC) system.

The ignition system uses a primary and secondary sub system in order to accomplish the timed spark distribution. The primary system consists of a low voltage trigger device which determines the base timing. This signal is modified by the ignition control driver (ICD) module. The signal travels to either or both the engine and transmission processor (control module) for base timing reference. Another signal is sent back to the ignition control driver (ICD) module, which has been adjusted by the control module (advanced or retarded) in order to trigger the coil, according to the requirements of the engine.

The secondary system consists of the ignition coil which has primary, or low voltage, windings and secondary, or high voltage, windings. The secondary side of the ignition coil generates a high voltage which high tension spark plug wires deliver to the spark plugs.

The control module controller now controls the ignition control (IC) and bypass functions.

In order to properly control the ignition and combustion timing, the control module needs to know the following things:

The crankshaft position
The engine speed or RPM
The engine load -- manifold pressure or vacuum
The atmospheric or barometric pressure
The engine coolant temperature
The camshaft position sensor
System Operation

The enhanced ignition system used on all OBD II engines somewhat resembles the current distributor ignition (DI) system described in the ignition systems. However, the system has been greatly enhanced in order to make it compatible with the new OBD II regulations. The enhanced ignition system provides a spark at precisely the correct time in order to ignite the air and fuel mixture for optimum performance and fuel economy. The system consists of the following components:

Vehicle control module (VCM)
Distributor
Ignition coil driver module
Ignition coil
Crankshaft position (CKP) sensor
This system does not use the ignition module used on the DI systems in the past. The VCM controller now controls the ignition control (IC) and bypass functions.

The crankshaft sensor, located in the front engine cover, is perpendicular to a target wheel attached to the crankshaft. The target wheel is equipped with slots situated 60 degrees apart. As the crankshaft rotates, the target wheel rotates past the crankshaft position sensor. The rising and falling edges created by the slots cause a signal to be sent back to the VCM. This signal occurs three times per crankshaft revolution and is referred to as the 3x signal for V6 applications. The signal occurs four times per crankshaft revolution and is referred to as the 4x signal for V8 applications.

The VCM then utilizes this 3x (V6) or 4x (V8) signal in order to provide the correct spark to the engine by way of the single coil driver module. The single coil driver module is basically an electronic switch that when commanded by the VCM, causes the primary coil voltage to breakdown, energizing the secondary coil and providing a spark via the coil wire to the distributor cap. The distributor consists of the following components:

Cap and rotor
Camshaft position (CMP) sensor
Gear drive and shaft
The camshaft drives the distributor shaft which rotates providing a spark to the correct cylinder by way of the cap and rotor. The camshaft position sensor functions much like the crankshaft sensor previously described but provides only a 1x signal to the VCM. That is, for every 2 rotations of the crankshaft, there is 1 rotation of the camshaft. Note that the CMP sensor will not affect driveability. The sole purpose of the CMP sensor is to provide the VCM with the necessary information for the misfire DTCs.

Ignition Control (IC)

The vehicle control module (VCM) software controls all of the ignition control (IC) and bypass functions. This reduces the number of circuits outside of the controller and ultimately reduces the possibility for shorts or opens in those circuits that could result in driveability complaints or diagnostic trouble codes (DTCs).

System Components

Crankshaft Position Sensor
Object Number: 12798 Size: SH
Click here for detailed picture of above image.
The crankshaft position (CKP) sensor is located in the front engine cover and is perpendicular to the crankshaft target wheel. The air gap between the sensor and the wheel is preset and not adjustable. The target wheel has four slots 60 degrees apart and is keyed to the crankshaft. As the target wheel rotates, the slots passing by the sensor create a change in the magnetic field of the sensor which results in an induced voltage pulse. One revolution of the crankshaft results in four pulses (4x signal). Based on these pulses, the VCM is able to determine crankshaft position and engine speed. The VCM then activates the fuel injector and provides a spark to the distributor. The relation between the CKP sensor and the target wheel is crucial. The sensor must be exactly perpendicular to the target wheel with the correct air gap.

Distributor
Object Number: 12796 Size: MH
Click here for detailed picture of above image.
The distributor is actually an assembly that contains the camshaft position (CMP) sensor, cap, rotor, and shaft. The distributor is splined by a helical gear to the camshaft and rotates providing a spark to each spark plug wire. When servicing the distributor, it is critical to ensure proper cap sealing to the distributor body and correct installation to the camshaft. If the distributor is installed a tooth off in relation to the camshaft, a DTC sets. The distributor is repairable.

Camshaft Position Sensor
Object Number: 12799 Size: MH
Click here for detailed picture of above image.
The camshaft position (CMP) sensor is located within the distributor. The operation is very similar to the crankshaft position (CKP) sensor however it provides one pulse per camshaft revolution (1x signal). This signal is not detrimental to the driveability of the vehicle. The VCM utilizes this signal in conjunction with the crankshaft position to determine which cylinders are misfiring.

Ignition Coil Driver Module and Ignition Coil
The ignition coil driver module is mounted on a bracket next to the coil. The VCM signals the ICD to turn ON primary current to the ignition coil by pulling the IC line high (4 volts). The ICD turns the primary current ON and OFF by applying and removing the ground to the primary winding at the appropriate time. This module is of minimum function. The module does not contain backup calibrations that allows the engine to continue to run if the IC signal is lost.

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Re: Ignition timing- what's normal?

Postby Clevis [OP] » April 10th 2014, 8:00pm

Thanks guys that's a big help. Timing is about normal...and advance is controlled by the ICM module that lives near the coils. When things are controlled by electronic modules it's just hard for me to visualize. Especially because the distributor is mechanical, the engine can't offset it's rotation does it? It just changes when it sends the spark through the coils? I guess I am thinking of the distributor like points, which set timing based on proximity, but maybe in the distributor the spark is allowed to jump different gap lengths.
So pinging sounds like "marbles in a coffee can"? I think I am going to hook up a voltmeter to my knock sensor and see if it thinks there is pinging at the same time I hear the sound.
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Re: Ignition timing- what's normal?

Postby chevymaher » April 10th 2014, 9:09pm

Clevis wrote:So pinging sounds like "marbles in a coffee can"?

Rattle, knock, marbles in a coffee can, Hammer beating on the side of the engine.
If your hearing something. Well your timing is in the detonation zone even if you were running the right gas. And for the engines compression with iron heads. 87 isn't it.
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Re: Ignition timing- what's normal?

Postby Corsemoto » April 10th 2014, 10:19pm

You don't say the mileage on your van but could be play in distributor, worn gear, etc. Also, if it just started recently it could be as simple as bad tank of gas.
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Re: Ignition timing- what's normal?

Postby Clevis [OP] » April 11th 2014, 12:05am

Corsemoto wrote:You don't say the mileage on your van but could be play in distributor, worn gear, etc. Also, if it just started recently it could be as simple as bad tank of gas.

The van is new to me, so I am going through all systems with a high level of paranoia. We plan on going on a 3500 mile trip to Canada in it soon as a camper. The van has 140k, it's on my "extra info" but I could list it somewhere else as well.
I just pulled the distributor last weekend to fix a broken screw mount on the housing. the distributor and wires look to be aftermarket and in decent condition, though the distributor looks like a "more affordable" version. But no carbon trails or excess build-up on the contacts. By "worn gear" do you mean at the base of the distributor?
The other caveat is these are sounds I am observing with the doghouse off. Since i have been doing regular work on it I have had it off for about 3 weeks. It actually has been sounding better as the tune-ups continue. But there's a couple sounds that kick in under load which don't sound so good. BUT these wouldn't typically be audible with the engine compartment closed, it's not that big of a knock.
I just read this in the owner's manual:

"If you’re using fuel rated at 87 octane or higher and you
hear heavy knocking, your engine needs service. But
don’t worry if you hear a little pinging noise when
you’re accelerating or driving up a hill. That’s normal,
and you don’t have to buy a higher octane fuel to get rid
of pinging. It’s the heavy, constant knock that means
you have a problem."

The latter description is what I am getting, I think the manual is instructing me to chill the eff out :)
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Re: Ignition timing- what's normal?

Postby chevymaher » April 11th 2014, 12:25am

It is saying check your knock sensors.
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Re: Ignition timing- what's normal?

Postby Clevis [OP] » April 11th 2014, 12:58am

how many do I have? I replaced one already that lives near the distributor
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Re: Ignition timing- what's normal?

Postby Corsemoto » April 11th 2014, 1:06am

Clevis wrote:The van has 140k, it's on my "extra info" but I could list it somewhere else as well.


Guess I missed that! :geek: :mrgreen:

[quote="Clevis"I just pulled the distributor last weekend to fix a broken screw mount on the housing. the distributor and wires look to be aftermarket and in decent condition, though the distributor looks like a "more affordable" version. But no carbon trails or excess build-up on the contacts. By "worn gear" do you mean at the base of the distributor?
[/quote]

Yeah, the cam gear at base of distributor. Since you pulled distributor, you would have noticed a chewed up gear I'm sure.

Not sure about early years, yours only has one the knock sensor I believe.

Check/clean EGR?
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Re: Ignition timing- what's normal?

Postby Clevis [OP] » April 11th 2014, 4:18pm

EGR- great minds think alike. I had pulled it at lunch yesterday and sat it in some carb cleaner for the afternoon, just the base. Which didn't work too well because the carb cleaner evaprorated. Finished the cleaning and installed last night.
We will see the effects.
If i test the condition through knock sensor (never done it), I guess I would create a wire setup so I can get the knock signal from positive wire while it's plugged in.
This van has been fun, I didn't know what PCV or EGR were a couple months ago. I have just been doing so much research.
Speaking of PCV- slight vacuum leak around it, I was thinking of replacing the rubber connector at the top of the PCV with 3/8" fuel line, I couldn't find a part for that.
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Re: Ignition timing- what's normal?

Postby ANTIQUECASTLE » November 5th 2014, 10:47pm

Doesn't the base timing have to be set? You know,,,tdc on #1 ,valves closed,rotor at #1 plug wire contact,,,,,
I have a old millennium Jeep and the base timing(engine off) was off.
I set it,and pick up was better.Perhaps apples and oranges......
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