Please explain IGN ADV - Actron9180

[sunfire]

I have an 05 Corolla (1ZZFE VVTi) that rough idles about 4-6 miles ~10 minutes into city driving from cold start on cold days (< 50F).

I'm a novice scan tool user. I paid a little extra for the Actron CP9180 (AAP sale) because it can view real-time and record data. There were no error codes no CEL. But I'm hoping the scan tool can pin point or explain the cause of the rough idle. Most of the PID are self explanatory.

However, the IGN ADV PID is a bit confusing. But probably has something to do with the VVTi (Toyota's intelligent Variable Valve Timing). The IGN ADV read 15 - 16 through my 6 mile trip to work. Can someone explain what this metric means? What is the unit of measurement? Is a reading of 15 - 16 for a 6 mile drive, good or bad?

 

[cchase]

IGN ADV is most likely ignition timing and the units are usually in degrees, though on your scan tool I am not sure if that is a raw value or if it is converted to appropriate units already.

 

[440Magnum]

Ignition advance is a measure how far before the piston reaches top-dead-center the spark plug fires. It is measured in degrees of crankshaft rotation, with zero being right at top-dead-center, positive numbers being before TDC, and negative numbers after TDC. You might naively think that the plug should fire right at or after the end of the compression stroke, but it actually needs to fire BEFORE the end of the compression stroke because it takes time for the fuel in the chamber to ignite and burn. You want peak PRESSURE just after top dead center, so you "light the fire" before the piston gets there. The amount of ignition advance depends on many things, like combustion chamber shape, valve timing, valve lift, cylinder diameter, number of spark plugs per cylinder etc. Generally, most engines need between 10 and 30 degrees of ignition advance- more advance under light load like cruising, less advance under heavy load like acceleration or towing. Also you typically need to add more advance as the engine RPM increases, so you see more advance at 3000 RPM than you do at idle. Also, the advance will be reduced if the knock sensor detects detonation.

I don't know what's considered "normal" for your engine, and to me (being an old-school big-bore engine, carburetor guy) 16 degrees sounds low... but it may be perfectly normal for a VVT-equipped modern small-bore engine- especially in low-speed city driving..

 

[gathermewool]

The ignition advance is the degrees before the piston reaches top-dead-center that the spark plug will fire. The higher the load or lower the RPM, the less advance. In your case, 15-16 degrees of advance for around-town driving at low speeds is normal, IMO, though though it shouldn't stay constant. When you let off the gas or at highway speeds, you should notice the advance climb into the 20s, then 30s and then into the 40s for low load highway driving.

 

[sunfire]

I peeked at the scan tool usually when I'm at a red light. Maybe the ignition advance value does vary more, I just didn't noticed it.

I'm heading out for my break, I'll have the scan tool hooked up.

Many thanks for your help. Your explanations were better than stuff I found on google.

 

[440Magnum]

Just be sure to watch the road and not the scan tool! Those things are more distracting than cell phones.

 

[Vikas]

Use the record function of that scanner, log the data and look at it afterward. Better, dump it here for all the critics to comment on!

I am seeing timing on my car (2000 Maxima) as high as 48 degrees under certain condition. It goes as low as -7 degrees under off throttle deceleration. At idle it is around 16 degrees. My car has "Recommended Premium" but I run it with regular. I was not able to ascertain timing advance difference with a premium tank.

I have set my ultra-gauge to display the timing advance, MAF reading, TPS, coolant temperature and fuel consumption. It is great fun to monitor them. It is significantly easier than the scanner.

- Vikas

 

[mechtech2]

440 and gathermewool said about all there is.

So advance is normal, from about 10 degrees at idle, to maybe 30-35 max under high RPM power. Cruising will show varied advance depending on speed and load - maybe 20-35 or more.

 

[CBR.worm]

Originally Posted By: Vikas
Use the record function of that scanner, log the data and look at it afterward. Better, dump it here for all the critics to comment on!

I am seeing timing on my car (2000 Maxima) as high as 48 degrees under certain condition. It goes as low as -7 degrees under off throttle deceleration. At idle it is around 16 degrees. My car has "Recommended Premium" but I run it with regular. I was not able to ascertain timing advance difference with a premium tank.

I have set my ultra-gauge to display the timing advance, MAF reading, TPS, coolant temperature and fuel consumption. It is great fun to monitor them. It is significantly easier than the scanner.

- Vikas


I'm surprised your car runs well on regular. My wife had an '00 maxima SE, with 93 octane it ran to redline in any gear perfectly smoothly. With 89 it had flat spots in the mid-RPM range at WOT. With 87 it ran badly. Our '95 and '97 were the same way.

 

[sunfire]

Originally Posted By: mechtech2
440 and gathermewool said about all there is.

So advance is normal, from about 10 degrees at idle, to maybe 30-35 max under high RPM power. Cruising will show varied advance depending on speed and load - maybe 20-35 or more.


I was only looking while I was at a light. So I never noticed the advance degrees change.

But I figured out the record data function. And at idle its around 15-16. Cruising in the city is between 20-32. When I floor it ~4K RPMs the advance actually dropped to about 15-18 range. But I don't usually drive at 4K RPMs so I'm not 100% sure about how my engine advances at those speeds.

 

[sunfire]

Originally Posted By: Vikas
I have set my ultra-gauge to display the timing advance, MAF reading, TPS, coolant temperature and fuel consumption. It is great fun to monitor them. It is significantly easier than the scanner.


They have ultra-gauge on "sale" now for $60 AR. Is that how much you paid for yours?

 

[Vikas]

Your timing looks very similar to mine. On mine too when you put the car under load, the timing is backed off by the ECM.

I paid introductory price of $40 after rebate + $8 shipping. If it ever gets to $40 again, I will pick few more for my other cars and/or as holiday present to family members.

Re: 2000 Maxima; I have only fed it regular after its first year. I guess the car never got addicted to the premium If I push the car, it will slam against the redline in first two gears without any trouble. I actually hate how it cuts off so violently at the redline. All I am saying is that with 87 octane, it has no trouble getting there or past the redline.

Only thing which I do lot more than other Maxima owners is that I generally overdose my vehicles with fuel system cleaners. It is as if I have addiction for them

- Vikas

 

[mechtech2]

Stepping on the gas and cruising will have very different ignition advance settings for the same RPM.
This is true for old mechanical and vacuum types, or computer mapped modern systems.
When cruising, the mixture is much less dense than when you step on it. It is also leaner than full throttle. Because of these things, it takes longer to burn/propagate across the combustion chamber. 40+ degrees is very expected when cruising.

Many modern cars have very castrated ignition advance curves. They don't know where the car will be driven, what quality of fuels are available, and have a great margin for error [safety].

That is why aftermarket tuning chips or programmers advance the timing. We used to do this with a turn of the distributor, or lighter advance springs. Now you gotta pay $400!