Reading Spark Plugs on 22re

[JZiggy]

So my 22re has an intermittent pre-ignition problem. It seems to happen on the highway, 2000-3000 rpm, at moderate throttle position. When it happens it will stop if I floor it.

The engine has about 40k on a rebuild, Engnldr 268 cam, fuel injectors have been serviced. It has plenty of power, gets decent mileage, and passes emissions. The EGR and PAIR system was recently removed. O2 sensor is also pretty new. Timing is set at 5* and the valve lash is set at IN/EX 7/9 thou. as per Engnbldr's recommendation.

Here are some pics of my spark plugs with 5k miles on them. They are the factory spec Denso's. Can one of you gurus take a look and see if they tell you anything about my pinging problem?

Only three because I dropped the 4th and messed it up

Closeup of #3

Closeup of #1

 

[Astro14]

What do you mean "EGR was removed"?

The distributor advance curve takes EGR into account...if you're running without EGR, you're going to have too much advance...and you guessed it, pre-ignition...

 

[spasm3]

#3 looks as if it has seen some oil. If you removed the egr system, then the egt is probably much higher that stock, i would go a heat range colder maybe 2 ranges colder on the plug. It goes away when you floor it, richer cooler mixture entering the cylinder. Egr does help lower the egt.

 

[mechtech2]

Removing the EGR made the engine more efficient in that range and now knocks at part throttle. There is more cylinder pressure at that point, now.
This is absolutely what is to be expected.

Recurve the distributor or put the EGR back on.
Maybe going up one step in octane would be best. the costs can be a wash if you get a bit better running.


The plugs are fine, but are getting a little dull. This increases the voltage necessary to fire them. Under load, they will eventually misfire as they wear.
File them sharp or get new ones. Or see if there is a double platinum available for longer life and better performance.

 

[tom slick]

Is the timing set at 5* with or without the vacuum hoses hooked to the dist.?

 

[JZiggy]

Wow thank for the fast responses, guys! I knew this was the place to ask!

I apologize as this was a copy-paste from a YotaTech.com thread I started earlier. The truck is an 88, and has EFI. The EGR was basically non-functional so I removed it. It still passes emissions LOL.

Thanks for the thoughts... keep em coming!

 

[Rican]

Have you been using fuel additives? If not, move to a colder plug. Any mods done to the engine that might have changed the compression?

 

[punisher]

Nothing overtly wrong with them, no signs of preignition/detonation. Doesn't mean it isn't happening, just means it isn't bad enough to show on your plugs yet. The discolorization is due to additives- sometimes yellow, sometimes red, even purple.

Reading plugs on a street driven vehicle is next to pointless. You might be able to pick out gross problems, oil consumption, constant detonation etc, but that's about it. Trying to read minutae from plugs that have to deal with idle/cruise/WOT conditions is about impossible. Thats the reason during drag races you shut the engine down as soon as you let out of the throttle so you don't confuse the spark plug reps/tech guys when they whip out their magnifiers to check your plugs for you. (Some of those techs are psychic I swear)

Different cam durations, valve lashes, cam timing adv or retarded, will effect cylinder pressures. Figure that EGR is also removed (not a smart move). Good cams are going to increase VE/combustion pressures in the midrange, thus meaning more pinging. Ignition timing should be checked when it is fully advanced, not at idle. Idle timing is only meaningful when you know your curve and your full advance. When you know what your timing is at cruise speed, at part throttle, then you have a number you can use.

 

[mechanicx]

Most likely you have too much ignition advance at cruise with all the mods and no EGR. Idealy the ECM should be reprogrammed for the mods. The O2 sensor is probably not allowing the engine to go too lean in cruise but those plugs look to me like they are running too hot. Maybe go one step colder but I think the ignition advance is the main problem.